To see the other types of publications on this topic, follow the link: 1/f noise spectroscopy.
Dissertations / Theses on the topic '1/f noise spectroscopy'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic '1/f noise spectroscopy.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Hassis, Wala. "Etude de structures avancées pour la détection IR quantique à haute température." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY013/document.
Full textAbstract:
La détection IR quantique met classiquement en jeu l'absorption de photons dans le matériau semi-conducteur II-VI CdHgTe. Cet alliage présente la particularité de permettre un ajustage du gap du semi-conducteur aux longueurs d'onde couvrant toute la gamme IR en jouant simplement sur la composition de l'alliage, ce qui en fait un matériau de choix. Cependant,les petits gaps en jeu ici imposent un refroidissement des plans focaux à des températures généralement cryogéniques (typiquement la centaine de Kelvins). Ce refroidissement représente naturellement une limite importante dans l'exploitation, l'encombrement et le coût de tels détecteurs.Un des grands défis à venir dans le domaine de la détection IR quantique est la détection à plus haute température. Une figure de mérite populaire pour examiner le fonctionnement de ces détecteurs est le courant d'obscurité qui reflète son bruit, dans le cas d'un détecteur limité par le bruit de courant (shot noise). Or, du fait des propriétés électriques du matériau semi-conducteur utilisé, ce courant d'obscurité augmente fortement avec le réchauffement du détecteur et rend son utilisation impossible à haute température. De plus, un autre phénomène apparaît également limiter le fonctionnement de nos photo-détecteurs : à hautes températures apparaît du bruit 1/f dont l'origine n'est pas parfaitement comprise aujourd'hui (matériau bulk ou interfaces, le débats reste ouvert…).Ce travail de thèse a pour objectif de comprendre les phénomènes physique régissant le bruit 1/f dans les photodiodes CdHgTe à travers la variation d'un bon nombre de paramètres physique et géométriques en vue de mettre en évidence la ou les corrélations de ce bruit avec ces variantes<br>The IR sensor makes quantum conventionally involves the absorption of photons in the semiconductor CdHgTe II -VI material . This alloy has a feature to allow an adjustment of the gap of the semiconductor at wavelengths covering the whole IR range by simply varying the composition of the alloy, which makes it a material of choice . However, small gaps at stake here impose a focal cooling to cryogenic temperatures generally planes ( typically hundred Kelvins ) . This cooling naturally represents an important limitation in the operation , the size and cost of such detectors .One of the great challenges ahead in the field of quantum IR detection is the detection at higher temperatures . A figure of merit for popular review the operation of these sensors is the dark current , which reflects its sound , in the case of a noise-limited current ( shot noise) detector. However, because the electrical properties of the semiconductor material used , the dark current increases sharply with the heating of the detector and makes it impossible to use at high temperature . In addition, another phenomenon also appears to limit the functionality of our photo-detectors: high temperature appears on the 1 / f noise whose origin is not fully understood today ( or bulk material interfaces , the debate remains open ... ) .To understand the physical phenomena governing the 1 / f noise in HgCdTe photodiodes through the variation this thesis aims to lots of physical and geometrical parameters in order to highlight the correlations or noise with these variants
2
Andreev, Alexey. "Šumová spektroskopie detektorů záření." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-233425.
Full textAbstract:
Kadmium telurid je velmi důležitý materiál jak základního, tak i aplikovaného výzkumu. Je to dáno zejména jeho výhodnými elektronickými, optickými a strukturními vlastnostmi, které ho předurčují pro náročné technické aplikace. Dnes se hlavně používá pro jeho vysoké rozlišení k detekci a X-záření. Hlavní výhodou detektorů na bázi CdTe je, že nepotřebují chlazení a mohou spolehlivě fungovat i při pokojové teplotě. To způsobuje efektivnější interakce fotonů než je tomu u Si nebo jiných polovodičových materiálů. Obsahem této práce byla analýza a interpretace výsledků získaných studiem šumových a transportních charakteristik CdTe vzorků. Měření ukázaly že odpor homogenní části CdTe krystalů mírně klesá při připojení elektrického pole na vzorku. Při změně teploty navíc dochází k odlišné reakci u CdTe typu p a n. Právě těmto efektům je v práci věnována pozornost. Pomocí šumové spektroskopie bylo zjištěno, že při nízkých frekvencích je u vzorků dominantní šum typu 1/f, zatímco při vyšších frekvencích je sledován generačně-rekombinační šum a tepelný šum. Všechny měřené vzorky vykazovaly mnohem vyšší hodnotu šumu na nízkých frekvencích než udává Hoogeova rovnice. Byly nalezeny a popsány zdroje nadbytečného šumu.
3
Toro, Clemente. "Improved 1/f noise measurements for microwave transistors." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000371.
Full text
4
Toro, Clemente Jr. "Improved 1/f Noise Measurements for Microwave Transistors." Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/1271.
Full textAbstract:
Minimizing electrical noise is an increasingly important topic. New systems and modulation techniques require a lower noise threshold. Therefore, the design of RF and microwave systems using low noise devices is a consideration that the circuit design engineer must take into account. Properly measuring noise for a given device is also vital for proper characterization and modeling of device noise. In the case of an oscillator, a vital part of a wireless receiver, the phase noise that it produces affects the overall noise of the system. Factors such as biasing, selectivity of the input and output networks, and selectivity of the active device (e.g. a transistor) affect the phase noise performance of the oscillator. Thus, properly selecting a device that produces low noise is vital to low noise design. In an oscillator, 1/f noise that is present in transistors at low frequencies is upconverted and added to the phase noise around the carrier signal. Hence, proper characterization of 1/f noise and its effects on phase noise is an important topic of research.
This thesis focuses on the design of a microwave transistor 1/f noise (flicker noise) measurement system. Ultra-low noise operational amplifier circuits are constructed and used as part of a system designed to measure 1/f noise over a broad frequency range. The system directly measures the 1/f noise current sources generated by transistors with the use of a transimpedance (current) amplifier. Voltage amplifiers are used to provide the additional gain. The system was designed to provide a wide frequency response in order to determine corner frequencies for various devices. Problems such as biasing filter networks, and load resistances are examined as they have an effect on the measured data; and, solutions to these problems are provided. Proper representation of measured 1/f noise data is also presented. Measured and modeled data are compared in order to validate the accuracy of the measurements. As a result, 1/f noise modeling parameters extracted from the measured 1/f noise data are used to provide improved prediction of oscillator phase noise.
5
Gesley, Mark Alan. "Spectral analysis of field emission flicker (1/f) noise." Full text open access at:, 1985. http://content.ohsu.edu/u?/etd,85.
Full text
6
Haigh, Mary K. "1/f noise in mercury cadmium telluride semiconductor diodes." Thesis, Heriot-Watt University, 2005. http://hdl.handle.net/10399/200.
Full text
7
Gross, Blaine Jeffrey. "1/f noise in MOSFETs with ultrathin gate dielectrics." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13192.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.<br>Includes bibliographical references (p. 176-184).<br>by Blaine Jeffrey Gross.<br>Ph.D.
8
Jong, Yeung-dong. "Fiber-optic interferometer for high 1/f noise environments /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
Full text
9
Tobias, David Andrew. "1/f noise and Luttinger liquid phenomena in carbon nanotubes." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7334.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.<br>Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
10
Siabi-Shahrivar, Nasser. "A study of 1/f noise in polysilicon emitter transistors." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314728.
Full text
11
Timpe, Jason T. (Jason Thomas) 1977. "Measurement and analysis of 1/f noise in uncooled microbolometers." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86827.
Full text
12
Kuhler, Kent A. (Kent Alan). "Design of a high speed 1/f noise test station." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43300.
Full text
13
Guinedor, Pierre. "Etude des bruits basse fréquence et des défauts électriquement actifs dans les détecteurs infrarouge refroidis." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT120.
Full textAbstract:
Dans le contexte des technologies HOT (High Operating Temperature) visant l’augmentation de la température de fonctionnement, les bruits basse fréquence 1/f et RTS (Random Telegraph Signal) sont les principaux détracteurs dégradant la qualité image des détecteurs infrarouge refroidis à base de HgCdTe. Ce travail est donc consacré à la détermination des défauts qui en sont à l’origine pour, à terme, pouvoir espérer améliorer la qualité image. A cette fin, deux voies d’étude ont été empruntées : la caractérisation électro-optique des bruits basse fréquence et la caractérisation spectroscopique des défauts électriquement actifs dans le matériau. Après avoir décrit les généralités sur la détection infrarouge et présenté les différentes techniques de spectroscopie employées lors de ce travail, les bruits basse fréquence sont étudiés pour affiner la compréhension de leur mécanisme physique. Enfin, des études de DLTS (Deep Level Transient Spectroscopy) sont menées pour deux technologie de fabrication en bande SWIR (Short Wave InfraRed, λc = 2,5 µm) et MWIR bleu (Mid Wave Infrared, λc = 4,2 µm) pour tenter de remonter aux défauts du matériau qui sont à l’origine de ces bruits<br>The current trend in the infrared market is to address HOT (High Operating Temperature) applications, which exacerbates the impact of low frequency noises (Random Telegraph Signal (RTS) and 1/f) and then degrades the image quality of cooled HgCdTe detectors. In this work, the focus was laid on the analysis of defects at the root of these noises to, eventually, improve the image quality. Two paths are introduced: the electro-optical characterization of low frequency noises and the spectroscopic characterization of electrically active defects in the material. First generalities on infrared detection and spectroscopic techniques used in this work are described. Then low frequency noises characterizations are realized to refine the comprehension of their physical mechanisms. Finally DLTS (Deep Level Transient Spectroscopy) studies are performed on two technologies for SWIR (Short Wave InfraRed, λc = 2.5 µm) and MWIR blue ((Mid Wave Infrared, λc = 4.2 µm) bands in order to get to the root of low frequency noises
14
Wang, Xiawa. "On the 1/f noise of atomic-layer-deposition metal films." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77000.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2012.<br>"February 2011." Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 77-81).<br>This thesis presents the measurement techniques and results of low-frequency noise for atomic-layer-deposition Pt films. Atomic-layer-deposition has been developed as an approach to make ultra-thin and conformal films. It has been employed to make detectors of bolometers. 1/f noise is a fundamental limit to the resolution. The experiments are designed to characterize the 1/f noise of the ALD fabricated Pt films. The measurement results show that for 7nm and 13nm ALD fabricated Pt films, 1/f noise is about two orders of magnitude larger than reported for continuous Pt films in literature. The thin film is also very likely to suffer from electromigration damage.<br>by Xiawa Wang.<br>M.Eng.
15
Matharoo, Rishi. "1/f Additive Phase Noise Analysis for One-Port Injection Locked Oscillators." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1430772754.
Full text
16
Liu, Chengxin. "Jitter in oscillators with 1/f noise sources and application to true RNG for cryptography." Link to electronic dissertation, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-011006-221104/.
Full text
17
Rodda, Lasya. "Baseband Noise Suppression in Ofdm Using Kalman Filter." Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc115147/.
Full textAbstract:
As the technology is advances the reduced size of hardware gives rise to an additive 1/f baseband noise. This additive 1/f noise is a system noise generated due to miniaturization of hardware and affects the lower frequencies. Though 1/f noise does not show much effect in wide band channels because of its nature to affect only certain frequencies, 1/f noise becomes a prominent in OFDM communication systems where narrow band channels are used. in this thesis, I study the effects of 1/f noise on the OFDM systems and implement algorithms for estimation and suppression of the noise using Kalman filter. Suppression of the noise is achieved by subtracting the estimated noise from the received noise. I show that the performance of the system is considerably improved by applying the 1/f noise suppression.
18
Jayaraman, Rajsekhar. "Reliability and 1/f noise properties of MOSFETs with nitrided oxide gate dielectrics." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/41582.
Full text
19
Cardon, Christopher Don. "1/f AM and PM noise in a common source heterojunction field effect transistor amplifier." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1317343431&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Full text
20
Chiteme, Cosmas. "The conductivity, dielectric constant 1/f noise and magnetic properties in percolating three-dimensional cellular composites." Thesis, University of the Witwatersrand, Johannesburg, 2000. http://hdl.handle.net/10539/21447.
Full textAbstract:
Thesis (Ph.D.)--University of the Witwatersrand, Science Faculty (Physics), 2000.<br>Percolation phenomena are studied in a series of composites, each with a cellular
structure (small conductor particles embedded on the surfaces of large insulator
particles). The DC and AC conductivities, l/f noise and magnetic properties (in some
series) are measured in the systems consisting of Graphite, Graphite-Boron Nitride,
Carbon Black, Niobium Carbide, Nickel and Magnetite (Fe304) as the conducting
components with Talc-wax (Talc powder coated with 4% wax by volume) being the
common insulating component. Compressed discs of 26mm diameter and about 3mm
thickness (with various conductor volume fractions covering both the insulating and
conducting region) were made from the respective powders at a pressure of 380MPa
and all measurements were taken in the axial (pressure) direction.
The conductivity (σm) and dielectric constant (εm) of percolation systems obey the
equations: σm = σc( ɸ - ɸc)t for ɸ >ɸc; σm = σi( ɸc - ɸ-s and εm = εi( ɸc - ɸ-s' for ɸ < ɸc;
outside of the crossover region given by ɸc± (δdc ~=(σi/σc)1/(t+s). Here ɸc is the critical
volume fraction of the conductor (with conductivity σ = σc) and cri is the conductivity
of the insulator, t and s are the conductivity exponents in the conducting and
insulating regions respectively and S’ is the dielectric exponent. The values of s and t
are obtained by fitting the DC conductivity results to the combined Percolation or the
two exponent phenomenological equations. Both universal and non-universal values
of the sand t exponents were obtained. The dielectric exponent S’, obtained from the
low frequency AC measurements, is found to be frequency-dependent. The real part
of the dielectric constant of the systems, has been studied as a function of the volume
fraction (ɸ) of the conducting component. In systems where it is measurable beyond
the DC percolation threshold, the dielectric constant has a peak at ɸ > ɸ, which
differs from key predictions of the original Percolation Theory. This behaviour of the
dielectric constant can be qualitatively modeled by the phenomenological two
exponent equation given in Chapter two of this thesis. Even better fits to the data are
obtained when the same equation is used in conjunction with ideas from Balberg's
extensions to the Random Void model (Balberg 1998a and 1998b).
At high frequency and closer to the percolation threshold, the AC conductivity and
dielectric constant follow the power laws: σm( ɸ,שּׂ) ~ שּׂX and εm( ɸ,שּׂ) ~ שּׂ-Y
respectively. In some of the systems studied, the x and y exponents do not sum up to
unity as expected from the relation x + y = 1. Furthermore, the exponent q obtained
from שּׂ x σm( ɸ,O)q in all but the Graphite-containing systems is greater than 1, which
agrees with the inter-cluster model prediction (q = (s + t)/t). The Niobium Carbide
system is the first to give an experimental q exponent greater than the value calculated
from the measured DC s and t exponents.
l/f or flicker noise (Sv) on the conducting side (ɸ > ɸc) of some of the systems has
been measured, which gives the exponents k and w from the well-established
relationships Sv/V2 = D(ɸ - ɸc)-k and Sv/V2 = KRw. V is the DC voltage across the
sample with resistance R while D and K are constants. A change in the value of the
exponent k and w has been observed with k taking the values kl ~ 0.92 - 5.30 close to
ɸc and k2 ~ 2.55 - 3.65 further into the conducting region. Values of WI range from
0.36 -1.1 and W2 ~ 1.2 - 1.4. These values of ware generally well within the limits of
the noise exponents proposed by Balberg (1998a and 1998b) for the Random Void
model. The t exponents calculated from k2 and W2 (using t = k/w) are self-consistent
with the t values from DC conductivity measurements. Magnetic measurements in
two of the systems (Fe304 and Nickel) show unexpected behaviour of the coercive
field and remnant magnetisation plotted as a function of magnetic volume fraction.
Fitting the permeability results to the two exponent phenomenological equation gives
t values much smaller than the corresponding DC conductivity exponents.
A substantial amount of data was obtained and analysed as part of this thesis.
Experimental results, mostly in the form of exponents obtained from the various
scaling laws of Percolation Theory, are presented in tabular form throughout the
relevant chapters. The results have been tested against various models and compare
with previous studies. While there is some agreement with previous work, there are
some serious discrepancies between the present work and some aspects of the
standard or original Percolation Theory, for example the dielectric constant behaviour
with conductor volume fraction close to but above ɸc. New results have also emerged
from the present work. This includes the change in the noise exponent k with (ɸ - ɸc),
the variation of the dielectric exponent s' with frequency and some DC scaling results
from the Fe304 system. The present work has dealt with some intriguing aspects of
Percolation Theory in real continuum composites and hopefully opened avenues for
further theoretical and experimental research.<br>AC 2016
21
Erturk, Mete. "The Bias Dependence of CMOS 1/F Noise Statistics, its Modeling and Impact on RF Circuits." ScholarWorks @ UVM, 2008. http://scholarworks.uvm.edu/graddis/79.
Full textAbstract:
In the last decade, wireless network routers, multi-media devices with Bluetooth© or similar communication capabilities, mobile cell-phones, and other “RF” devices have found widespread use in the consumer market. The integration and cost advantages of CMOS-only chips have attracted circuit designers in academia and industry, and CMOS technology is now a strong contender along with BiCMOS, and III-V semiconductors for analog / mixed signal and radio frequency applications. RF CMOS technology has numerous advantages that come with the feasibility of system-on-chip. These advantages include reduced fabrication cost and reduced pin count due to die sharing between analog and digital portions. Perhaps the most critical disadvantage of RF CMOS is the very high 1/f noise levels observed in MOSFETs in comparison to BJTs (bipolar-junction transistor). The silicon – silicondioxide interface is crucial to the operation of all MOSFETs, and unlike bipolar devices, MOSFETs are largely surface conductive devices, with device current flowing at or near the interface. This leads to the large 1/f noise associated with FETs. There has been on-going research to study the physical mechanism of 1/f noise. The compact models used to predict device noise in circuit simulations have also been improved. It has recently been observed that 1/f noise increases during the lifetime of a transistor. Also, large statistical variations in noise level have been reported. The existing models fail to explain such variability in 1/f noise. The work presented here extends the state-of-the art of 1/f noise modeling through experimental and theoretical analysis of noise reliability and statistics. A new model is developed based on a novel theory that investigates the relationship between the spatial profile of interface traps and the bias dependence of 1/f noise. The theory is tested against device noise measurements, as well as RF circuit phase noise measurements.
22
Mayorov, Alexander. "Tunnelling and noise in GaAs and graphene nanostructures." Thesis, University of Exeter, 2008. http://hdl.handle.net/10036/46914.
Full textAbstract:
Experimental studies presented in this thesis have shown the first realisation of resonant tunnelling transport through two impurities in a vertical double-barrier tunnelling diode; have proved the chiral nature of charge carriers in graphene by studying ballistic transport through graphene $p$-$n$ junctions; have demonstrated significant differences of $1/f$ noise in graphene compared with conventional two-dimensional systems. Magnetic field parallel to the current has been used to investigate resonant tunnelling through a double impurity in a vertical double-barrier resonant tunnelling diode, by measuring the current-voltage and differential conductance-voltage characteristics of the structure. It is shown that such experiments allow one to obtain the energy levels, the effective electron mass and spatial positions of the impurities. The chiral nature of the carriers in graphene has been demonstrated by comparing measurements of the conductance of a graphene $p$-$n$-$p$ structure with the predictions of diffusive models. This allowed us to find, unambiguously, the contribution of ballistic resistance of graphene $p$-$n$ junctions to the total resistance of the $p$-$n$-$p$ structure. In order to do this, the band profile of the $p$-$n$-$p$ structure has been calculated using the realistic density of states in graphene. It has been shown that the developed models of diffusive transport can be applied to explain the main features of the magnetoresistance of $p$-$n$-$p$ structures. It was shown that $1/f$ noise in graphene has much more complicated concentration and temperature dependences near the Dirac point than in usual metallic systems, possibly due to the existence of the electron-hole puddles in the electro-neutrality region. In the regions of high carrier concentration where no inhomogeneity is expected, the noise has an inverse square root dependence on the concentration, which is also in contradiction with the Hooge relation.
23
Ghosh, Santunu. "Study on the origin of 1/f in bulk acoustic wave resonators." Thesis, Besançon, 2014. http://www.theses.fr/2014BESA2046/document.
Full textAbstract:
Depuis quelques décennies, la technologie de contrôle de la fréquence a été au coeur de l'électronique des tempsmodernes grâce à son vaste domaine d'applications dans les systèmes de communication, les ordinateurs, les systèmesde navigation ou de défense militaire. Les dispositifs temps-fréquence fournissent des stabilités de fréquence et despuretés spectrales élevées dans le domaine de la stabilité court-terme. L'amélioration de la performance de cesdispositifs reste un grand défi pour les chercheurs. La réduction du bruit afin d'augmenter cette stabilité court-terme etd'éviter les commutations non souhaitées entre les canaux est donc très souhaitable. Il est communément admis que lalimitation fondamentale à cette stabilité court-terme est due au bruit flicker de fréquence des résonateurs. Dans cemanuscrit, un premier chapitre rappelle quelques faits de base sur l’acoustique, la cristallographie et les définitions dudomaine temps-fréquence nécessaires à l’étude des résonateurs et oscillateurs ultra-stables. Le deuxième chapitre estconsacré à un résumé de la littérature sur le bruit de fréquence en 1/f. Ensuite, le troisième chapitre concerne nos étudessur le modèle quantique de bruit en 1/f du Pr. Handel, qui, bien que critiqué par beaucoup, est encore le seul qui fournitune estimation de l'amplitude de plancher de bruit en 1/f et qui n'est pas infirmé par les données expérimentales. Dans lequatrième chapitre, une autre approche, basée sur le théorème de fluctuation-dissipation, est utilisée afin de mettre descontraintes numériques sur un modèle de bruit en 1/f causé par une dissipation interne (ou de structure) proportionnelleà l'amplitude, et non à la vitesse. Le dernier chapitre est consacré aux résultats expérimentaux. Le design et lesparamètres du résonateur ultra-stable utilisé lors de cette étude sont décrits. Les mesures de bruit de phase sur plusieurslots de résonateurs sont données. Les mesures des paramètres de résonateur ont été effectuées à basse température afinde les corréler avec les résultats de bruit. Afin d'évaluer rapidement la qualité des différents résonateurs, une autreapproche dans le domaine temporel a été testée. Elle utilise des oscillations pseudo-périodiques transitoires mettant lesoscilloscopes numériques actuellement disponibles à leurs limites de capacité. Enfin, les conclusions et perspectivessont présentées<br>Since a few decades, frequency control technology has been at the heart of modern day electronics due to its huge areaof applications in communication systems, computers, navigation systems or military defense. Frequency controldevices provide high frequency stabilities and spectral purities in the short term domain. However, improvement of theperformance of these devices, in terms of frequency stability, remains a big challenge for researchers. Reducing noise inorder to increase the short term stability and avoid unwanted switching between channels is thus very desirable. It iscommonly admitted that the fundamental limitation to this short-term stability is due to flicker frequency noise in theresonators. In this manuscript, a first chapter recalls some basic facts about acoustic, crystallography and definitions oftime and frequency domain needed to explore ultra-stable resonators and oscillators. The second chapter is devoted to asummary of the literature on flicker frequency noise. Then, the third chapter concerns our studies on Handel’s quantum1/f noise model, which although criticized by many, is still the only one that provides an estimation of the flooramplitude of 1/f noise that is not invalidated by experimental data. In the fourth chapter, another approach, based on thefluctuation-dissipation theorem, is used in order to put numerical constraints on a model of 1/f noise caused by aninternal (or structural) dissipation proportional to the amplitude and not to the speed. The last chapter is devoted toexperimental results. An ultra-stable resonator used during this study is described. Phase noise measurements on severalbatches of resonators are given. Measurements of resonator parameters have been done at low temperature in order tocorrelate them with noise results. Another approach with a procedure that use transient pseudo periodic oscillations andput to their limits the capacities of presently available digital oscilloscopes, is presented, in order to assess rapidly thequality of various resonators. Finally, conclusions and perspectives are given
24
Wu, Junjie. "The conductivity, dielectric constant, magnetoresistivity, 1/f noise and thermoelectric power in percolating randomgraphite-- hexagonal boronnitride composites." Thesis, University of the Witwatersrand, 1997. http://hdl.handle.net/10539/19443.
Full textAbstract:
ii
ABSTRACT
Percolation phenomena involving the electrical conductivity, dielectric constant,
Hall coefficient, magnetoconductivity, relative magnetoresistivity, 1/ f noise and thermoelectric power are investigated in graphite (G) and hexagonal boron-nitride (BN)
powder mixtures. Two kinds of systems are used in the experiments: highly compressed
discs and parallelepipeds, cut from these discs, as well as 50%G-50%BN and 55%G-45%BN powder mixtures undergoing compression.
The measured DC conductivities follow the power-laws 0"( <p, 0) ex: (<p-<Pc)t (<p > <Pc)
and O"(<p, 0) ex: (<Pc-<Pti (<p < <Pc), and the low frequency (lOOHz & 1000Hz) dielectric constant varies as c( <p, W ~ 0) ex: (<Pc - <P )-S( <P < <Pc), where <Pc is the percolation threshold, t and s are the conductivity exponents, and s is the dielectric exponent.
Near the percolation threshold and at high frequencies, the AC conductivity varies with frequency as 0"( <p, w) ex: WX and the AC dielectric constant varies as c( <p, w) ex: w-Y,
where the exponents x and y satisfy the scaling relation x + y = 1. The crossover frequency We scales with DC conductivity as Wc ex: O"q( <p, 0) (<p > <Pc), while on the
insulating side, Wc ~ 1, resulting in q ~O for the three G-BN systems. The loss tangent tan t5( <p, w) (<p < <Pc) is found to have a global minimum, in contrary to the results of computer simulations.
The Hall constant could not be measured using existing instrumentation. The measured magnetoconductivity and relative magnetoresistivity follow the power-laws - 6. 0" ex: (<p - <Pc)3.08 and 6.R/ R ex: (<p - <Pc)O.28 respectively. These two exponents, iii 3.08 and 0.28, are not in agreement with theory.
The 1/ f noise was measured for the conducting discs and parallelepipeds. The normalized 1/ f noise power varies as Sv I V2 ex RW with the exponents w = 1.47 and
1.72 for the disc and parallelepiped samples respectively. Furthermore, the normalized
noise power near the percolation threshold is, for the first time, observed to vary
inversely with the square-root of sample volume.
Based on the Milgrom-Shtrikman-Bergman-Levy (MSBL) formula, thermoelectric
power of a binary composite is shown to be a linear function of the WiedemanFranz
ratio. A scaling scheme for the Wiedeman-Franz ratio for percolation systems
is proposed, which yields power-law behavior for the thermoelectric power. The
proposed power-laws for the thermoelectric power can be written as (Sm - Md ex
(<p - <Pc)h 1 for <P > <Pc and as (Sm - /~1d ex (<Pc - <p)-h2 for <p < <Pc, where Sm is
the thermoelectric power for the composites, Afl is a constant for a given percolation
system, and hI and h2 are the two critical exponents. The experimental thermoelectric
power data for the G-BN conducting parallelepipeds was fitted to the above powerlaw
for <p > <Pc. A least squares fit yielded the exponent hI = -1.13 and parameter
MI =9.511l V I I< respectively.
25
Testa, Joseph Anthony. "Experimental studies of 1/f noise in high-critical-temperature superconductors in the normal and superconducting states /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487587604133792.
Full text
26
Both, Thiago Hanna. "Autocorrelation analysis in frequency domain as a tool for MOSFET low frequency noise characterization." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/174487.
Full textAbstract:
O ruído de baixa frequência é um limitador de desempenho em circuitos analógicos, digitais e de radiofrequência, introduzindo ruído de fase em osciladores e reduzindo a estabilidade de células SRAM, por exemplo. Transistores de efeito de campo de metalóxido- semicondutor (MOSFETs) são conhecidos pelos elevados níveis de ruído 1= f e telegráfico, cuja potência pode ser ordens de magnitude maior do que a observada para ruído térmico para frequências de até dezenas de kHz. Além disso, com o avanço da tecnologia, a frequência de corner —isto é, a frequência na qual as contribuições dos ruídos térmico e shot superam a contribuição do ruído 1= f — aumenta, tornando os ruídos 1= f e telegráfico os mecanismos dominantes de ruído na tecnologia CMOS para frequências de até centenas de MHz. Mais ainda, o ruído de baixa frequência em transistores nanométricos pode variar significativamente de dispositivo para dispositivo, o que torna a variabilidade de ruído um aspecto importante para tecnologias MOS modernas. Para assegurar o projeto adequado de circuitos do ponto de vista de ruído, é necessário, portanto, identificar os mecanismos fundamentais responsáveis pelo ruído de baixa frequência em MOSFETs e desenvolver modelos capazes de considerar as dependências do ruído com geometria, polarização e temperatura. Neste trabalho é proposta uma técnica para análise de ruído de baixa frequência baseada na autocorrelação dos espectros de ruído em função de parâmetros como frequência, polarização e temperatura. A metodologia apresentada revela informações importantes sobre os mecanismos responsáveis pelo ruído 1= f que são difíceis de obter de outras formas. As análises de correlação realizadas em três tecnologias CMOS comerciais (140 nm, 65 nm e 45 nm) fornecem evidências contundentes de que o ruído de baixa frequência em transistores MOS tipo-n e tipo-p é composto por um somatório de sinais telegráficos termicamente ativados.<br>Low-frequency noise (LFN) is a performance limiter for analog, digital and RF circuits, introducing phase noise in oscillators and reducing the stability of SRAM cells, for example. Metal-oxide-semiconductor field-effect-transistors (MOSFETs) are known for their particularly high 1= f and random telegraph noise levels, whose power may be orders of magnitude larger than thermal noise for frequencies up to dozens of kHz. With the technology scaling, the corner frequency — i.e. the frequency at which the contributions of thermal and shot noises to noise power overshadow that of the 1= f noise — is increased, making 1= f and random telegraph signal (RTS) the dominant noise mechanism in CMOS technologies for frequencies up to several MHz. Additionally, the LFN levels from device-to-device can vary several orders of magnitude in deeply-scaled devices, making LFN variability a major concern in advanced MOS technologies. Therefore, to assure proper circuit design in this scenario, it is necessary to identify the fundamental mechanisms responsible for MOSFET LFN, in order to provide accurate LFN models that account not only for the average noise power, but also for its variability and dependences on geometry, bias and temperature. In this work, a new variability-based LFN analysis technique is introduced, employing the autocorrelation of multiple LFN spectra in terms of parameters such as frequency, bias and temperature. This technique reveals information about the mechanisms responsible for the 1= f noise that is difficult to obtain otherwise. The correlation analyses performed on three different commercial mixed-signal CMOS technologies (140-nm, 65-nm and 40-nm) provide strong evidence that the LFN of both n- and p-type MOS transistors is primarily composed of the superposition of thermally activated random telegraph signals (RTS).
27
Viklund, Jonas. "Developing of an ultra low noise bolometer biasing circuit." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296698.
Full textAbstract:
Noise in electronic circuits can sometimes cause problems. It is especially problematic in for example high sensitive sensors and high end audio and video equipment. In audio and video equipment the noise will make its way into the sound and picture reducing the overall quality. Sensors that are constructed to sense extremely small changes can only pick up changes larger than the noise floor of the circuit. By lowering the noise, sensors can achieve higher accuracy. This thesis presents an ultra low noise solution of the biasing circuitry to the bolometer used in one of FLIR Systems high end cameras. The bolometer uses different adjustable direct current voltage sources and is extremely sensitive to noise. The purpose is to improve the picture quality and the thermal measurement resolution. A prototype circuit was constructed and in the end of the thesis a final circuit with successful result will be presented.
28
Macků, Robert. "Analýza fluktuačních procesů v solárních článcích." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-233560.
Full textAbstract:
The thesis deals issue of the silicon solar cells non-destructive testing. The manufacturing technology of solar cells currently features a very high level of perfection. Its further development appears to be limited by amongst other issues imperfect diagnostic methods. The objective of presented research consists in non-destructive studies of processes that influence specimen life and reliability. To this end, I will employ mainly noise based analytical methods in connection with observation of defect optical activities, capacitance measurement etc. These methods are closely related to some specimen bulk imperfections, crystal-lattice defect induced traps, local-stress-subjected regions and, finally, breakdowns, which might bring about specimen destruction. Based on a detailed study and understanding of transport processes, regions in which noise is generated can be identified and appropriate technological measures can be proposed and adopted. Presented research focuses, first of all, on the real solar cell structures, which are inhomogeneous in their nature and are difficult to diagnose. The significant part of this study is attend to the random n-level (in most case just two-level) impulse noise, usually referred to as microplasma noise. This noise is a consequence of local breakdowns in micro-sized regions and brings about reduction of lifetime or destruction of the pn junction. The micro-sized regions have been studied separately by electrical and optical methods and defect properties have been put forward. Nevertheless, no less significant part of the thesis is devoted to the fluctuation modeling of the bulk imperfections in the semi-analytical form.
29
Babcock, Jeffrey Archimedes 1961. "Characterization of the effects of radiation-induced charge on the 1/f noise properties of power DMOS transistors." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277934.
Full textAbstract:
This thesis investigates the effects of ionizing radiation on the noise properties of n-channel power DMOS transistors. The pre-irradiation noise power spectral density of these transistors was found to vary as 1/ flambda where lambda (the slope of the noise power spectral density when plotted on a log-log scale) ranged from approximately 0.5 to 1.0. Radiation-induced trapped charge density was found to have a large effect on the magnitude and slope of the noise. Irradiation of devices was found to produce a more uniform distribution in time constants leading to the more ideal 1/f noise power spectrum as total dose increased. Polarity of bias applied during post-radiation anneal was found to force a distribution in time constants leading to an increase in lambda for devices under negative gate bias and a decrease in lambda for devices under positive gate bias. Radiation hardness of power MOSFETs was investigated as a function of their pre-irradiation 1/f noise. No correlation was found between noise magnitude and device hardness.
30
Naude, Natali. "Proton magnetic resonance spectroscopy to evaluate in vivo breast tissue chemistry at 3.0 Tesla." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/225943/1/Natali_Naude_Thesis.pdf.
Full textAbstract:
The research utilised in vivo 2D magnetic resonance spectroscopy in conjunction with standard breast MRI to investigate MR-visible characteristics associated with breast density and menopausal status. Statistically significant differences were recorded in various neutral lipids and metabolites, and with further development, may enable non-contrast MRI to evaluate breast cancer risk, avoiding the use of gadolinium-based contrast media. The tentative assignment of methylmalonic acid (MMA), which has been associated with cancer proliferation, was also made. Another spectral region was identified relating to polyunsaturated fatty acid content in breast tissue. PUFAs have been shown to have a protective effect against breast cancer.
31
Jin, Zhenrong. "Low-Frequency Noise in Silicon-Germanium BiCMOS Technology." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4827.
Full textAbstract:
Low-frequency noise (LFN) is characterized using in-house measurement systems in a variety of SiGe HBT generations. As technology scales to improve the performance and integration level, a large low-frequency noise variation in small geometry SiGe HBTs is first observed in 90 GHz peak fT devices. The fundamental mechanism of this geometry dependent noise variation is thought to be the superposition of individual Lorentzian spectra due to the presence of G/R centers in the device. The observed noise variation is the result of a trap quantization effect, and is thus best described by number fluctuation theory rather than mobility fluctuation theory. This noise variation continues to be observed in 120 GHz and 210 GHz peak fT SiGe HBT BiCMOS technology. Interestingly, the noise variation in the 210 GHz technology generation shows anomalous scaling behavior below about 0.2-0.3um2 emitter geometry, where the noise variation rapidly decreases. Data shows that the collector current noise is no longer masked by the base current noise as it is in other technology generations, and becomes the dominant noise source in these tiny 210 GHz fT SiGe HBTs. The proton response of LFN in SiGe HBTs is also investigated in this thesis. The results show that the relative increase of LFN is minor in transistors with small emitter areas, but significant in transistors with large emitter areas after radiation. A noise degradation model is proposed to explain this observed geometry dependent LFN degradation. A 2-D LFN simulation is applied to SiGe HBTs for the first time in order to shed light on the physical mechanisms responsible for LFN. A spatial distribution of base current noise and collector current noise reveals the relevant importance of the physical locations of noise sources. The impact of LFN in SiGe HBTs on circuits is also examined. The impact of LFN variation on phase noise is demonstrated, showing VCOs with small geometry devices have relatively large phase noise variation across samples.
32
Franceschin, Alessandro. "Ultra-Low Noise Oscillators enabling Frequency Generation for Radar Systems in Scaled CMOS Technologies." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422821.
Full textAbstract:
In those systems where it is important to synthesize a precise frequency signal, such as the carrier of a transmission system, phase noise is certainly one of the most important aspects that define the performance. Because of the ever increasing data rate in modern communication systems (5G), the interest of low phase noise frequency synthesizer is high. Radar systems are another example in which the phase noise has an important role: by exploiting the Doppler effect, informations on distance and speed of the target are obtained by comparing the frequency of the transmitted and received signal. Radar systems are precise but also expensive due to their complexity. As an example, radar are used in air plane to detect perturbations. In recent years, however, radar systems have also been spreading in the automotive field, as advanced driving assistance systems (ADAS). Although this is not new: the first car to have a radar system appeared in the market in 1990, only luxury models were employing radar. Nowadays, ultrascaled CMOS technology has made the widespread deployment of radar on low-cost cars economically advantageous. The challenge is to obtain good performances comparable with bipolar technology. For this reason, oscillators, which are the heart of a frequency synthesizer, in CMOS technology, are the main topic of this thesis. After a brief introduction about the operating principle of a typical car radar, we enter into the merits of the design of an analog circuit by developing a methodology to identify the optimum oscillation frequency, that is, the frequency that allows us to obtain the best performance. Then the designs of two oscillator topologies are described, both operating at 20GHz: the first is a hybrid class B/D oscillator, while the second one a class C. The latter in particular proves to be effective in reducing the contribution of the flicker noise from the active devices, one of the biggest imitations of modern CMOS technologies. Finally, a method to extract the fourth harmonic from the class C oscillator is presented. This allows to employ the class C oscillator for automotive radar application, as described by regulations.<br>In qualunque sistema in cui sia necessario generare una segnale di frequenza preciso, come ad esempio la portante di un sistema di trasmissione, il rumore di fase è certamente uno degli aspetti più importanti che definiscono le prestazioni dell’apparato. L’interesse per sistemi a basso rumore di fase è al giorno d’oggi grande vista la diffusione di sistemi di comunicazione 5G. Un’altra applicazione in cui questo è importante è nei sistemi radar, dove sfruttando l’effetto Doppler, le informazioni su distanza e velocita del bersaglio vengono ottenute dal confronto tra frequenza del segnale trasmesso e ricevuto. Il radar è un apparato di misura preciso ma anche complesso e perciò costoso; in ambito civile trova applicazione soprattutto a bordo di aerei per individuare, ad esempio, perturbazioni meteo. Negli ultimi anni però, si sta assistendo alla diffusione di sistemi radar anche nel campo automibilistico, come sistemi di aiuto alla guida, i così detti ADAS. Per quanto questo non sia nuovo, la prima auto ad avere un sistema radar è comparsa nel mercato nel 1990, solo modelli di lusso montavano questi sistemi. Ora la tecnologia CMOS ha raggiunto una maturità tale da rendere econimicamente vantaggiosa la diffusione su larga scala di radar anche su auto a basso costo. La sfida è quella di ottenere prestazioni da tecnologie digitali CMOS comparabili a quelle a bipolari. Per questo motivo, questa tesi, tratta di oscillatori, che sono il cuore di un sintetizzatore di frequenza, realizzati in tecnologia CMOS. Dopo una breve introduzione su quello che è il principio di funzionamento di un tipico radar per auto, si entra nel merito del design di un circuito analogico sviluppando una metodologia per individuare la frequenza di oscillazione ottima, cioè quella frequenza che consente di ottenere le prestazioni migliori. Dopodiché vengono descritti i design di due topologie di oscillatori entrambi operanti a 20GHz: il primo è un ibrido classe B/D, il secondo un classe C. Quest’ultimo in particolare si dimostra essere efficace a ridurre il contributo del rumore flicker dei dispostivi attivi, uno dei più grossi limiti delle tecnologie CMOS moderne. Infine viene mostrato un metodo per estrarre una componente di quarta armonica, ovvero a 80 GHz, dall’oscillatore in classe C cosicché il radar possa operare a frequenze concesse dalle normative.
33
Bennett, Marc. "Synthesis of high temperature superconductors HgBaâ†2CuOâ†4â†+â†#delta# and YBaâ†2Cuâ†3Oâ†7â†-#delta# and characterisation by 1/f noise." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297841.
Full text
34
Olyaei, Maryam. "Low-frequency noise in high-k gate stacks with interfacial layer engineering." Doctoral thesis, KTH, Integrerade komponenter och kretsar, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177911.
Full textAbstract:
The rapid progress of complementary-metal-oxide-semiconductor (CMOS) integrated circuit technology became feasible through continuous device scaling. The implementation of high-k/metal gates had a significantcontribution to this progress during the last decade. However, there are still challenges regarding the reliability of these devices. One of the main issues is the escalating 1/fnoise level, which leads to degradation of signal-to-noise ratio (SNR) in electronic circuits. The focus of this thesis is on low-frequency noise characterization and modeling of various novel CMOS devices. The devices include PtSi Schottky-barriers for source/drain contactsand different high-kgatestacksusingHfO2, LaLuO3 and Tm2O3 with different interlayers. These devices vary in the high-k material, high-k thickness, high-k deposition method and interlayermaterial. Comprehensive electrical characterization and low-frequency noise characterization were performed on various devices at different operating conditions. The noise results were analyzed and models were suggested in order to investigate the origin of 1/f noise in these devices. Moreover, the results were compared to state-of-the-art devices. High constant dielectrics limit the leakage current by offering a higher physical dielectric thickness while keeping the Equivalent Oxide Thickness (EOT) low. Yet, the 1/f noise increases due to higher number of traps in the dielectric and also deterioration of the interface with silicon compared to SiO2. Therefore, in order to improve the interface quality, applying an interfacial layer (IL) between the high-k layer and silicon is inevitable. Very thin, uniform insitu fabricated SiO2 interlayers with HfO2 high-k dielectric have been characterized. The required thickness of SiO2 as IL for further scaling has now reached below 0.5 nm. Thus, one of the main challenges at the current technology node is engineering the interfacial layer in order to achieve both high quality interface and low EOT. High-k ILs are therefore proposed to substitute SiOx dielectrics to fulfill this need. In this work, we have made the first experiments on low-frequency noise studies on TmSiO as a high-k interlayer with Tm2O3 or HfO2 on top as high-k dielectric. The TmSiO/Tm2O3 shows a lower level of noise which is suggested to be related to smoother interface between the TmSiO and Tm2O3. We have achieved excellentnoise performancefor TmSiO/Tm2O3 and TmSiO/HfO2 gate stacks which are comparableto state-of-the-art SiO2/HfO2 gate stacks.<br><p>QC 20151130</p>
35
Calabrese, Joseph John. "Three dimensional random percolating composites : electrical and mechanical properties of metal/high temperature superconductor composites and 1/F noise in metal/insulator composites /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487673114112979.
Full text
36
Husák, Marek. "Využití šumové diagnostiky k analýze vlastností solárních článků." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217922.
Full textAbstract:
The master’s thesis deals with the noise diagnostic in the solar cells. Describes the main kinds of noises. The samples were quality and reliability screened using noise reliability indicators. The samples were surveyed by measuring the I-V characteristics, the noise spectral density as a function of forward voltage and frequency. It was calculated the noise spectral density as a function of forward current.
37
Sassine, Gilbert. "Etude du transport et du bruit dans les couches 2D de nanotubes de carbone." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20182/document.
Full textAbstract:
Les travaux de la thèse ont porté sur l'étude, la réalisation, la caractérisation et la modélisation de films 2D à base de nanotubes de carbone. Dans le premier chapitre nous avons présenté des généralités sur les nanotubes de carbone. Ensuite, nous nous sommes intéressés aux jonctions nanotube-nanotube et plus particulièrement à la modélisation du transport dans les différents types de jonction (M/M), (M/SC) et (SC/SC). Avec le deuxième chapitre nous avons entamé l'étude des films 2D à base de nanotubes de carbone. Dans un premier temps nous nous sommes intéressés au transport électrique dans ces structures fortement inhomogènes, en particulier en décrivant les modèles analytiques rendant compte du phénomène de percolation tant au niveau de la conductance que du bruit en 1/f. La seconde partie du chapitre est entièrement consacrée à la fabrication et la caractérisation physico-chimique des films 2D L'objectif principal du troisième chapitre est la modélisation des films 2D de nanotubes de carbone. Par rapport aux autres modèles utilisés dans la littérature, le modèle développé dans cette partie est le seul à prendre en compte la nature physique de chaque jonction tube-tube : (M/M) ou (M/SC) ou (SC/SC). Notre modèle prend ainsi en compte les non linéarités des jonctions. La résolution numérique de ce système est optimisée : i) en utilisant la technique MNA, technique dont le principe consiste à linéariser chaque dipôle du circuit. ii) en parallélisant les calculs sur un cluster informatique d'une centaine de cœurs. Pour le calcul du bruit la même technique est utilisée mais avec, dans ce cas, l'utilisation de la méthode du réseau adjoint. Dans le quatrième chapitre, nous avons, dans un premier temps, présentés et analysés nos résultats expérimentaux concernant la mesure de la conductance et du bruit en 1/f. Quelles que soient les conditions de dépôt nous avons toujours observé un comportement de type percolation au niveau des grandeurs mesurées, conductance et niveau de bruit en 1/f. Nous avons utilisé les paramètres d'ajustement des lois de percolation pour comparer et analyser nos résultats. Il en ressort que l'impact du surfactant sur l'homogénéité de la solution, se retrouve au niveau des résultats électriques des couches déposées, montrant l'avantage d'utiliser du sel biliaire. Quant à l'influence de la densité des tubes, comme attendu, la conductance augmente avec celle-ci. Par contre nous avons remarqué que le bruit en 1/f était beaucoup plus sensible à ce paramètre, avec en particulier un changement significatif au niveau des paramètres de percolation en bruit mis en évidence à forte densité de nanotubes. La deuxième partie de ce chapitre est dédiée à la simulation des paramètres électriques de nos structures expérimentales. Nous avons paramétré l'énergie et la largeur des barrières de potentiel entre chaque jonction. Ces paramètres sont ajustés à partir des résultats expérimentaux et sont fonction de la nature du surfactant. Les résultats de ces simulations concernant la conductance et le niveau de bruit en 1/f s'accordent avec les mesures et dans tous les cas les lois de percolation macroscopique sont respectées, ce qui valide nos modèles ainsi que la possibilité d'intégrer de façon réaliste la différence structurale des surfactants. Pour rendre compte de la déviation de la loi macroscopique de percolation du bruit en 1/f, observée sur les films déposés à partir de solution à forte densité de surfactant, nous avons au niveau des simulations introduit et modulé le nombre d'amas (clusters) de nanotubes en fonction de la densité des couches. Là encore le bon accord observé avec les résultats expérimentaux nous permet de valider la présence d'inhomogénéités dues aux clusters de nanotubes dans nos dépôts<br>In this thesis we have focused on the fabrication, the characterization, and the modeling of 2D films based on carbon nanotubes.In the first chapter, we have presented general informations on carbon nanotubes. Then we are interested in the nanotube-nanotube junctions and particularly the modeling of transport in different types of junction (M/M), (M/SC) and (SC/SC).In the second chapter we have presented a study of 2D films based on carbon nanotubes. At first we present the electrical transport in these structures strongly inhomogeneous, especially in describing the analytical models accounting for the percolation phenomenon both in the conductance and 1/f noise. The second part of the chapter is devoted entirely to the manufacture and physico-chemical characterization of 2D films.The main objective of the third chapter is the modeling of 2D films of carbon nanotubes. Compared to other models described in the literature, the model developed in this section is the only one that take into account the physical nature of each tube-tube junction (M/M) or (M/SC) or (SC/SC). Our model takes into account the junction nonlinearity. The numerical solution of the system is optimized: i) using the MNA technique whose principle is to linearize each dipole in the circuit. ii) parallelizing computations on a computer cluster of a hundred core. For the noise simulation, the same technique is used but in this case, we have used the adjoint network method. In the fourth chapter, we have, at first, presented and analyzed our experimental results for conductance and 1/f noise. Whatever the deposition conditions we always observed a percolation-like behavior of our results. We used the fitting parameters of the percolation laws to compare and analyze our results. It appears that the impact of the surfactant on the homogeneity of the solution is found in the electrical measurement results of deposited films. As for the influence of the density of the tubes, as expected, the conductance increases with the increase of nanotubes density. We noticed that the 1/f noise was much more sensitive to this parameter, with in particular a significant change in the noise percolation parameters revealed at high density of nanotubes. The second part of this chapter is dedicated to the simulation of the electrical parameters of our experimental structures. These parameters are adjusted on the basis of experimental results and are based on the nature of the surfactant. The results of these simulations for the conductance and 1/f noise agree with measurements and in all cases the macroscopic percolation laws are respected, which validate our models. To bring to the fore the deviation from the noise percolation law observed in films deposited from solution with a high density of surfactant, we have introduced in our simulated structures a number of clusters of nanotubes according to the density of the deposited layers. Once again we observed a good agreement with the experimental results allowing us to validate the presence of clusters of nanotubes in our deposited films
38
Majzner, Jiří. "Elektronický šum piezokeramických snímačů akustické emise." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-233423.
Full textAbstract:
In our work the analysis of electrical and noise characteristics of piezoceramic acoustic emission sensors is accomplished. The objective of our work is to analyze and optimize the signal-to-noise ratio. The starting point is the explanation of the noise origin in the acoustic emission sensors. The voltage fluctuation is caused by the dipole vibrations due to their interaction with phonons. The frequencies of dipoles vibrations have statistical distribution and the total energy of these vibrations is proportional to the temperature. The statistical distribution of vibration frequencies leads to the origination of the 1/f type noise spectral density. The interaction between the phonons and electric dipoles is characterized by the imaginary part of susceptibility which is related to the transformation of electric energy to the mechanical energy of vibrations. This process is irreversible and this forms important theoretical question whether the Callen-Welton fluctuation dissipation theorem could be used for the description of fluctuation processes in the acoustic emission sensors. In our work the influence of the real and imaginary part of the susceptibility on the noise and electrical characteristics is solved, the dissipation of electrical energy characterized by the imaginary part of susceptibility is described and the connection between the imaginary part of susceptibility and the noise power spectral density is discussed. Due to the fact that these processes originate in the interaction between electrical dipoles and phonons, we give account of the temperature dependencies of equivalent series resistance and power spectral density of noise voltage, respectively. Piezoceramics stiffness contribute significantly to the resonance creation hence the pressure influence on the sensor noise characteristics was studied. The signal-to-noise ration improvement requires the piezoceramic sample diameter increase for its constant thickness. The ratio of the noise spectral density and sensitivity is independent on the sample thickness. The noise voltage is proportional to the square root of spectral density and frequency bandwidth that is why for the high signal-to-noise ratio it is necessary to minimize the signal amplifier frequency bandwidth. The noise voltage power spectral density increases with the temperature while the activation energy is 20 meV for the temperature 300 K, and 80 meV for the temperature 400 K, respectively. The power spectral density of planar oscillations decreases with increasing pressure and simultaneously the resonant frequency increases. The bandwidth of the normalized spectral density increases with the pressure for the planar oscillations while is invariable for the thickness oscillations. For the examination of the influence of the piezoceramic electrical polarization on the electrical and noise characteristics the experimental study of these dependencies was accomplished for samples without polarization, and samples polarized by electric field EP = 500V/mm and 1000V/mm, respectively. The samples without polarization show the noise of 1/f type only which corresponds to the Callen-Welton fluctuation dissipation theorem. The polarization leads to the generation of planar and thickness oscillations and the power spectral density of voltage fluctuation on the electrodes is proportional to the temperature, and inversely proportional to the imaginary part of permittivity, to the sample area S, and the frequency f.
39
Amon, Mary Jean. "Examining Coordination and Emergence During Individual and Distributed Cognitive Tasks." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1468336815.
Full text
40
Mouchel, Myckael. "Développement de jonctions tunnel magnétiques bas bruit pour les capteurs de champ magnétique." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY104.
Full textAbstract:
Les capteurs de champ magnétique à base de jonctions tunnel magnétiques sont parmi les solutions les plus prometteuses dans le cadre de la miniaturisation toujours plus poussée des composants. Crocus Technology, entreprise partenaire de cette thèse, conçoit depuis plusieurs années des capteurs parmi les plus petits du marché. Malgré leur très bonne sensibilité, ils présentent un bruit en 1/f très important dégradant fortement leur capacité à détecter des champs magnétiques de faible amplitude. Les travaux de cette thèse s’inscrivent dans un contexte de réduction du bruit et d’amélioration de la détection de ces capteurs. Des études approfondies du bruit dans les capteurs commerciaux de Crocus ont été conduites afin de bâtir une bonne compréhension des mécanismes à l’origine de ce bruit. Ces études ont été menées grâce à un banc d’expérience spécifiquement destiné à la réalisation de mesures de bruit conjointement à une caractérisation magnéto-électrique des échantillons. Ainsi, nous avons pu relier le bruit mesuré au comportement des capteurs sous différentes conditions de champ magnétique en développant un modèle explicatif sur la base de « l’empreinte des propriétés magnétiques des échantillons sur leur bruit ». Cette thèse s’est achevée par un projet 6-sigma piloté par l’auteur et ayant permis de mettre en place les solutions nécessaires à la réalisation d’un objectif ambitieux de réduction du bruit. La détectivité a ainsi pu être améliorée de presque deux ordres de grandeur et ainsi atteindre les 13 nT/√Hz à 10 Hz en l’espace de quelques mois, sans dégrader l’intégrabilité des capteurs et en respectant des contraintes industrielles<br>Magnetic tunnel junctions based magnetic field sensors are one of the most promising solutions in the framework of electronic components miniaturization. Crocus Technology, the industrial stakeholder of this thesis, has been designing some of the market smallest TMR sensors for several years. Despite their good sensitivity, they exhibit a large 1/f noise, deteriorating their capability to detect low magnetic fields. This thesis falls within a context of noise reduction and detection improvement of the sensors. In-depth noise studies of existing sensors have been performed in order to better apprehend the origins of such noise. These studies have been carried out thanks to a specifically designed experimental bench allowing simultaneous noise and magneto-electrical characterizations of the devices. Thereby, we have been able to link the observed noise to the response of the sensors under specific magnetic field conditions by developing an illustrative model based on “magnetic-to-noise fingerprint of the sensors”. This thesis was further completed by a 6-sigma project, led by the author, which allowed us to implement the needful solutions to answer an ambitious objective of noise reduction. The detectivity has been improved by nearly two orders of magnitude, thus reaching 13 nT/√Hz at 10 Hz in a few months, without deteriorating the integrability of the sensors while satisfying industrial constraints
41
Šik, Ondřej. "Studium šumových charakteristik detektorů radioaktivního záření." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218099.
Full textAbstract:
The main goal of this Master’s thesis is to describe relationship between low frequency noise spectral characteristics of Cadmium-Telluride radiation detectors depending on applied voltage and detectors reaction to illumination of various wavelengths. Also, the reaction and influence of higher operating temperatures were investigated. The noise measurements shown that the dominant noise type at low frequencies is the 1/f noise. Several samples with different resistivity were tested. By comparing results, we are able to estimate the quality of detectors and their sensibility to illumination and higher operating temperatures. We have found that all the studied CdTe detectors are sensitive to one particular wavelength of 548nm. Resulting data were processed by EasyPlot program that provided graphical representation of spectral noise characteristics. All measured characteristics of tested samples are compared and it’s estimated the similarity between the samples.
42
von, Haartman Martin. "Low-frequency noise characterization, evaluation and modeling of advanced Si- and SiGe-based CMOS transistors." Doctoral thesis, KTH, Mikroelektronik och Informationsteknik, IMIT, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3888.
Full textAbstract:
A wide variety of novel complementary-metal-oxide-semiconductor (CMOS) devices that are strong contenders for future high-speed and low-noise RF circuits have been evaluated by means of static electrical measurements and low-frequency noise characterizations in this thesis. These novel field-effect transistors (FETs) include (i) compressively strained SiGe channel pMOSFETs, (ii) tensile strained Si nMOSFETs, (iii) MOSFETs with high-k gate dielectrics, (iv) metal gate and (v) silicon-on-insulator (SOI) devices. The low-frequency noise was comprehensively characterized for different types of operating conditions where the gate and bulk terminal voltages were varied. Detailed studies were made of the relationship between the 1/f noise and the device architecture, strain, device geometry, location of the conduction path, surface cleaning, gate oxide charges and traps, water vapour annealing, carrier mobility and other technological factors. The locations of the dominant noise sources as well as their physical mechanisms were investigated. Model parameters and physical properties were extracted and compared. Several important new insights and refinements of the existing 1/f noise theories and models were also suggested and analyzed. The continuing trend of miniaturizing device sizes and building devices with more advanced architectures and complex materials can lead to escalating 1/f noise levels, which degrades the signal-to-noise (SNR) ratio in electronic circuits. For example, the 1/f noise of some critical transistors in a radio receiver may ultimately limit the information capacity of the communication system. Therefore, analyzing electronic devices in order to control and find ways to diminish the 1/f noise is a very important and challenging research subject. We present compelling evidence that the 1/f noise is affected by the distance of the conduction channel from the gate oxide/semiconductor substrate interface, or alternatively the vertical electric field pushing the carriers towards the gate oxide. The location of the conduction channel can be varied by the voltage on the bulk and gate terminals as well by device engineering. Devices with a buried channel architecture such as buried SiGe channel pMOSFETs and accumulation mode MOSFETs on SOI show significantly reduced 1/f noise. The same observation is made when the substrate/source junction is forward biased which decreases the vertical electric field in the channel and increases the inversion layer separation from the gate oxide interface. A 1/f noise model based on mobility fluctuations originating from the scattering of electrons with phonons or surface roughness was proposed. Materials with a high dielectric constant (high-k) is necessary to replace the conventional SiO2 as gate dielectrics in the future in order to maintain a low leakage current at the same time as the capacitance of the gate dielectrics is scaled up. In this work, we have made some of the very first examinations of 1/f noise in MOSFETs with high-k structures composed by layers of HfO2, HfAlOx and Al2O3. The 1/f noise level was found to be elevated (up to 3 orders of magnitude) in the MOSFETs with high-k gate dielectrics compared to the reference devices with SiO2. The reason behind the higher 1/f noise is a high density of traps in the high-k stacks and increased mobility fluctuation noise, the latter possibly due to noise generation in the electron-phonon scattering that originates from remote phonon modes in the high-k. The combination of a TiN metal gate, HfAlOx and a compressively strained surface SiGe channel was found to be superior in terms of both high mobility and low 1/f noise.<br>QC 20100928
43
Dong, Quan. "HEMTs cryogéniques à faible puissance dissipée et à bas bruit." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112035.
Full textAbstract:
Les transistors ayant un faible niveau de bruit à basse fréquence, une faible puissance de dissipation et fonctionnant à basse température (≤ 4.2 K) sont actuellement inexistants alors qu’ils sont très demandés pour la réalisation de préamplificateurs à installer au plus près des détecteurs ou des dispositifs à la température de quelques dizaines de mK, dans le domaine de l’astrophysique, de la physique mésoscopique et de l’électronique spatiale. Une recherche menée depuis de nombreuses années au LPN vise à réaliser une nouvelle génération de HEMTs (High Electron Mobility Transistors) cryogéniques à haute performance pour répondre à ces demandes. Cette thèse, dans le cadre d’une collaboration entre le CNRS/LPN et le CEA/IRFU, a pour but la réalisation de préamplificateurs cryogéniques pour des microcalorimètres à 50 mK.Les travaux de cette thèse consistent en des caractérisations systématiques des paramètres électriques et des bruits des HEMTs (fabriqués au LPN) à basse température. En se basant sur les résultats expérimentaux, l’une des sources de bruit à basse fréquence dans les HEMTs a pu être identifiée, c’est-à-dire la part du courant tunnel séquentiel dans le courant de fuite de grille. Grâce à ce résultat, les hétérostructures ont été optimisées pour minimiser le courant de fuite de grille ainsi que le niveau de bruit à basse fréquence. Au cours de cette thèse, différentes méthodes spécifiques ont été développées pour mesurer de très faibles valeurs de courant de fuite de grille, les capacités du transistor et le bruit 1/f du transistor avec une très haute impédance d’entrée. Deux relations expérimentales ont été observées, l’une sur le bruit 1/f et l’autre sur le bruit blanc dans ces HEMTs à 4.2 K. Des avancées notables ont été réalisées, à titre d’indication, les HEMTs avec une capacité de grille de 92 pF et une consommation de 100 µW peuvent atteindre un niveau de bruit en tension de 6.3 nV/√Hz à 1 Hz, un niveau de bruit blanc de 0.2 nV/√Hz et un niveau de bruit en courant de 50 aA/√Hz à 10 Hz. Enfin, une série de 400 HEMTs, qui répondent pleinement aux spécifications demandées pour la réalisation de préamplificateurs au CEA/IRFU, a été réalisée. Les résultats de cette thèse constitueront une base solide pour une meilleure compréhension du bruit 1/f et du bruit blanc dans les HEMTs cryogéniques afin de les améliorer pour les diverses applications envisagées<br>Transistors with low noise level at low frequency, low-power dissipation and operating at low temperature (≤ 4.2 K) are currently non-existent, however, they are widely required for realizing cryogenic preamplifiers which can be installed close to sensors or devices at a temperature of few tens of mK, in astrophysics, mesoscopic physics and space electronics. Research conducted over many years at LPN aims to a new generation of high-performance cryogenic HEMTs (High Electron Mobility Transistors) to meet these needs. This thesis, through the collaboration between the CNRS/LPN and the CEA/IRFU, aims for the realization of cryogenic preamplifiers for microcalorimeters at 50 mK.The work of this thesis consists of systematic characterizations of electrical and noise parameters of the HEMTs (fabricated at LPN) at low temperatures. Based on the experimental results, one of the low-frequency-noise sources in the HEMTs has been identified, i.e., the sequential tunneling part in the gate leakage current. Thanks to this result, heterostructures have been optimized to minimize the gate leakage current and the low frequency noise. During this thesis, specific methods have been developed to measure very low-gate-leakage-current values, transistor’s capacitances and the 1/f noise with a very high input impedance. Two experimental relationships have been observed, one for the 1/f noise and other for the white noise in these HEMTs at 4.2 K. Significant advances have been made, for information, the HEMTs with a gate capacitance of 92 pF and a consumption of 100 µW can reach a noise voltage of 6.3 nV/√ Hz at 1 Hz, a white noise voltage of 0.2 nV/√ Hz, and a noise current of 50 aA/√Hz at 10 Hz. Finally, a series of 400 HEMTs has been realized which fully meet the specifications required for realizing preamplifiers at CEA/IRFU. The results of this thesis will provide a solid base for a better understanding of 1/f noise and white noise in cryogenic HEMTs with the objective to improve them for various considered applications
44
Agnaou, Abicha. "Elaboration et caractérisation de AZO 2% en couches minces et son application à la détection de gaz par la mesure du bruit basse fréquence." Thesis, Littoral, 2019. http://www.theses.fr/2019DUNK0548.
Full textAbstract:
Dans ce travail, nous avons réalisé et caractérisé des couches minces de AZO pour des applications capteurs ultrasensibles fonctionnant à la température ambiante. La méthode de détection des gaz choisie est la méthode de mesure du bruit basse fréquence (BF). L'élaboration du matériau est réalisée au moyen d'un bâti de pulvérisation cathodique RF à magnétron. Nous avons investigué l’effet de différents paramètres de dépôt sur la résistivité électrique afin de trouver un compromis entre eux et nous conduire à une faible résistivité. Pour cela, nous avons étudié l’influence de l’épaisseur des couches minces de AZO (50 nm à 450 nm) sur les propriétés structurales, morphologiques, électriques (en continu et bruit BF). Puis une étude de l’effet de la puissance RF de dépôt et du recuit post-dépôt sur les différentes propriétés est présentée. Les propriétés de détection de la série AZO à épaisseurs variables à la température ambiante en présence d’argon ou d’oxygène à différentes pressions par la méthode du bruit BF sont exposées. Une plateforme d'analyse des gaz contenant l'ensemble de l'instrumentation associée à notre capteur a été développée et présentée. Nous avons étudié en détail la réponse de la série de AZO en fonction de l’épaisseur sous différentes pressions l’oxygène injectées, et évalué les performances des différents capteurs. Les résultats obtenus ont montré que la détection de l’oxygène par la mesure de bruit BF est plus sensible que par la méthode en continue. Nous avons conclu de cette étude que : i) le niveau du bruit en 1/f mesuré pour un courant continu donné en présence de l’oxygène diminué par rapport à son niveau atteint à l’air ambiant, ii) la sensibilité Gₙₒᵢₛₑ augmente avec l’augmentation de l’épaisseur de la couche active de AZO du capteur, iii) la sensibilité Gₙₒᵢₛₑ augmente avec la pression d’oxygène puis sature, iv) le temps de réponse (temps d'attente pour atteindre l'état stationnaire pour le bruit) augmente avec l’augmentation de l’épaisseur de la couche active<br>In this work, we realized and characterized thin films of AZO for ultra-sensitive sensor applications operating at ambient temperature. The gas detection method chosen is the method of measuring low frequency noise (LF). The development of the material is carried out by means of a magnetron RF sputtering frame. We investigated the effect of different deposition parameters on electrical resistivity in order to find a compromise between them and lead us to a low resistivity. For this, we studied the influence of the thickness of thin films of AZO (50 nm to 450 nm) on the structural, morphological, electrical properties (in continuous and noise LF). Then a study of the effect of RF deposition power and post-deposit annealing on the different properties is presented. The detection properties of the AZO series with varying thicknesses at room temperature in the presence of argon or oxygen at different pressures by the LF noise method are exposed. A gas analysis platform containing all the instrumentation associated with our sensor has been developed and presented. We have studied in detail the response of the AZO series as a function of the thickness under different injected oxygen pressures, and evaluated the performance of different sensors. The results obtained showed that the detection of oxygen by the measurement of LF noise is more sensitive than by the continuous method. We concluded from this study that: i) the noise level in 1/f measured for a given direct current in the presence of oxygen decreased compared to its level reached in the ambient air, ii) the sensitivity Gₙₒᵢₛₑ increases with the increase in the thickness of the active layer of AZO of the sensor, iii) the sensitivity Gₙₒᵢₛₑ increases with the pressure of oxygen then saturates, iv) the response time increases with increasing thickness of the active layer
45
Castillo, Guevara Ramon D. "Coordination of Local and Global Features: Fractal Patterns in a Categorization Task." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1321372828.
Full text
46
Unver, Alper. "Determination Of Stochastic Model Parameters Of Inertial Sensors." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615548/index.pdf.
Full textAbstract:
ABSTRACT
DETERMINATION OF STOCHASTIC MODEL PARAMETERS OF INERTIAL SENSORS
Ü<br>nver, Alper
PhD, Department of Electric Electronic Engineering
Supervisor: Prof. Dr. Mü<br>beccel Demirekler
January 2013, 82 pages
Gyro and accelerometer systematic errors due to biases, scale factors, and misalignments can be compensated via an on-board Kalman filtering approach in a Navigation System. On the other hand, sensor random noise sources such as Quantization Noise (QN), Angular Random Walk (ARW), Flicker Noise (FN), and Rate Random Walk (RRW) are not easily estimated by an on-board filter, due to their random characteristics.
In this thesis a new method based on the variance of difference sequences is proposed to compute the powers of the above mentioned noise sources. The method is capable of online or offline estimation of stochastic model parameters of the inertial sensors. Our aim in this study is the estimation of ARW, FN and RRW parameters besides the quantization and the Gauss-Markov noise parameters of the inertial sensors.
The proposed method is tested both on the simulated and the real sensor data and the results are compared with the Allan variance method. Comparison shows very satisfactory results for the performance of the method. Computational load of the new method is less than the computational load of the Allan variance on the order of tens.
One of the usages of this method is the individual noise characterization. A noise, whose power spectral density has a constant slope, can be identified accurately by the proposed method. In addition to this, the parameters of the GM noise can also be determined.
Another idea developed here is to approximate the overall error source as a combination of ARW and some number of GM sources only. The reasons of selecting such a structure is the feasibility of using these models in a Kalman filter framework for error propagation as well as their generality of modeling other noise sources.
47
RANIERI, IZILDA M. "Crescimento de cristais de LiY sub(1-x) TR sub(x) F sub(4):Nd (TR=Lu ou Gd) para aplicacoes opticas." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10935.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:45:47Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:07:17Z (GMT). No. of bitstreams: 1
07149.pdf: 7899411 bytes, checksum: 6ba368602f98f29e9401ef54276cdb45 (MD5)<br>Tese (Doutoramento)<br>IPEN/T<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
48
Guillaumont, Marc. "Variantes d’oxydes de métaux de transition : relations entre structure, transport et performances bolométriques." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI022.
Full textAbstract:
La détection infrarouge, autrefois réservée aux applications militaires et spatiales, connait depuis une dizaine d’années une mutation importante et s’ouvre de plus en plus vers des marchés "grand public". Cette démocratisation est principalement liée aux développements rapides que connaissent les technologies utilisant des bolomètres "non refroidis", qui profitent de leurs compatibilités avec les filières de la microélectronique.La technologie utilisée au CEA/LETI repose sur l’utilisation d’un matériau thermomètre à base de silicium amorphe (également noté "a-Si"). Ce dernier comporte de nombreux avantages dont, principalement, son excellente compatibilité avec les outils "classiques" de la microélectronique. Cependant, l’intégration d’un matériau thermomètre plus performant que le a-Si est nécessaire pour répondre aux défis à venir.Conscient de l’importance de cette problématique "matériau" le laboratoire CEA/LETI développe depuis plusieurs années des matériaux à base d’oxydes de métaux de transition déposés en couches minces.Cette étude s’appuie sur l’ensemble des variantes d’oxydes de métaux de transition étudié dans ce cadre. Cette palette de matériaux, qui se sont révélés très différents dans leur structure et, corrélativement, les mesures de transport dans chacun de ces types, nous ont permis de relier structure et mécanismes de conduction spécifiques à chacun. Une attention particulière a été portée aux mesures de TCR, ou « Temperature Coefficient of Resistance », (facteur à maximiser) et de bruit en 1/f (source de bruit à minimiser), les deux paramètres de choix pour le matériau thermistor.Des grandes tendances qui pilotent la performance d’un matériau thermistor pour la bolométrie ont pu être déduites de ces investigations. Les travaux présentés dans cette thèse permettent d’évaluer le potentiel de tel ou tel compétiteur avant d’en entreprendre le développement<br>InfraRed detection, formerly reserved to defense and spatial applications, is currently undergoing deep changes which open new opportunities. Uncooled microbolometer technologies, compatible with classical semiconductors processes, are now able to produce low cost thermal imagers and this will open the door to customer markets in a close future.The technology developed in the CEA/LETI laboratory use the amorphous silicon (noted "a-Si") as the thermistor material. This material has many advantages, in particular, its excellent compatibility with the classical tools used in microelectronic industry. However, better performance in the thermistor material is still needed to address future applications.To handle this challenge, CEA/LETI laboratory is currently developing thermistors made of transition metal oxides thin films. The study presented hereby is based on various transition metal oxides samples deposited in the CEA/LETI Laboratory.Characterization of the structure and the electronic transport for each of these samples allowed us to put in evidence correlations between microscopic structure and conduction mechanisms. Two main figures of merit impacting the overall material performance were investigated : the TCR, Temperature Coefficient of Resistance (which must be maximized) and the 1/f noise (which must be minimized).Finally we conclude this work by highlighting majors outlines governing the performance of a thermistor
49
Bourgeois, Florian. "Développement de matériaux thermistors pour applications bolométriques." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENI069.
Full textAbstract:
La technologie des microbolomètres est à ce jour la plus avancée pour l'imagerie IR non refroidie. Le LETI développe une technologie basée sur l'utilisation du silicium amorphe comme matériau thermistor. L'introduction d'un matériau alternatif doit permettre de poursuivre l'amélioration des performances. Cette étude considère une solution alternative à base de films minces d'oxydes nanocristallins. Deux procédés sont envisagés : le dépôt IBS et le dépôt MOCVD. L'étude des procédés ainsi que la caractérisation des matériaux ont permis la maîtrise et la compréhension des évolutions structurales et fonctionnelles mises en jeux. Des caractérisations électriques (résistivité, TCR, bruit en 1/f) sur dispositifs ont permis de débattre de l'intérêt de ces nouveaux matériaux. Une réflexion a été menée sur les relations microstructure-propriétés<br>Microbolometers FPAs are nowadays the most advanced technology for uncooled IR imaging. Developments at CEA-LETI are based on the use of amorphous silicon as thermistor material. Introduction of an alternative material is necessary to keep on improving detectors performances. This study considersnanocrystalline oxides thin films as an alternative material. Two deposition techniques have been studied : IBS and MOCVD. Process studies as well as materials characterizations allowed us to control and understand the involved micro-structural evolutions. Electrical characterizations (resistivity, TCR, 1/f noise) on integrated devices were achievedin order to estimate the potential of these new materials. Microstructure-property relationships are also discussed
50
Pokharel, Alok. "Analyse par des méthodes de “reverse engineering” de résonateurs piézoélectriques hautes performances et modélisation du bruit." Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCD025.
Full textAbstract:
Les résonateurs à ondes acoustiques de volume (BAW) ont été étudiés dans le domaine temps-fréquence à FEMTO-ST depuis longtemps et ont montré un rôle essentiel dans de nombreuses applications métrologiques telles que dans les dispositifs de positionnement comme GPS, Glonass, Galileo, etc. Ce travail de thèse présente la technique passive utilisée pour des mesures du bruit de phase dans les résonateurs BAW à quartz. Les résonateurs BAW de hautes performances ont été fabriqués par plusieurs fabricants européens et fournis par le CNES pour une étude de “reverse engineering” durant cette thèse. Le manuscrit commence par rappeler les bases de cristallographie du quartz, de piézoélectricité et de caractérisation du bruit dans les résonateurs ultra-stables. La deuxième partie du travail donne des détails sur la mesure de bruit dans les résonateurs par une technique de suppression de porteuse et sur une adaptation pour les résonateurs LGT d’impédance très faible (< 10 ohms).La troisième partie concerne l’interprétation avec le modèle de Steven-Tiersten des résultats de mesures du bruit de phase à différentes températures et leur classification en fonction du bruit. Une simulation par méthode d’éléments finis (FEM) permet de comparer ces résultats avec la théorie de Steven-Tiersten. La quatrième partie, présente un test de modélisation du bruit de phase à l'aide d’un modèle d’intermittence. Des comparaisons de nos résultats avec la distribution de Mittag-Leffler ainsi que des distributions stables semblent indiquer un rejet du modèle d’intermittence en loi de puissance, dans notre cas. Enfin, le travail de “reverse engineering” est réalisé en démontant les résonateurs pour l'analyse des défauts par diffraction des rayons X et diffusion laser. Le démontage du résonateur a révélé des imperfections macroscopiques. Les résultats préliminaires de diffraction des rayons X montrent la présence de dislocations qui pourraient être une cause de bruit de phase dans les résonateurs. Ceci devra être confirmé sur d’autres résonateurs<br>Bulk Acoustic Wave Resonators (BAW) have been studied in Time and Frequency domain for a long time, particularly at FEMTO-ST. They have an essential role in many metrological applications such as in positioning devices like GPS, Glonass, Galileo, etc. This thesis work presents the passive technic used for phase noise measurement in high-performance BAW resonators. These resonators were fabricated by several European manufacturers and provided for the thesis work by CNES for reverse engineering investigations.The work begins with recalling the basics of piezoelectricity in quartz and noise in ultra-stable resonators.The second part of the work gives details on noise measurement by carrier suppression technic with an alternative technic for low impedance resonators (< 10 ohms).The third part is about the comparison of Steven-Tiersten’s model with our phase noise measurement results at different temperatures and classification of resonators according to their short-term stability. A finite element simulation is used to compare the theory and experimental results.The fourth part presents tests using Mittag-Leffler distribution and stable distributions of a model of phase noise due to power law intermittency.Finally, the “reverse engineering” work is carried out by dismantling some resonators for defects analysis using X-rays diffraction and laser scattering. This revealed macroscopic imperfections and a few dislocations which could be a possible cause for phase noise in the resonators. This will have to be confirmed and quantified with other resonators