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Artykuły w czasopismach na temat "Electron Conduction - Disordered System"
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Xu, Hui, Yi-pu Song i Xin-mei Li. "Conduction mechanism studies on electron transfer of disordered system". Journal of Central South University of Technology 9, nr 2 (czerwiec 2002): 134–37. http://dx.doi.org/10.1007/s11771-002-0058-3.
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Efros, A. L., i B. I. Shklovskii. "Influence of electron-electron interaction on hopping conduction of disordered systems". Journal of Non-Crystalline Solids 97-98 (grudzień 1987): 31–38. http://dx.doi.org/10.1016/0022-3093(87)90010-x.
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Maiti, Santanu K. "Quantum Transport in Bridge Systems". Solid State Phenomena 155 (maj 2009): 71–85. http://dx.doi.org/10.4028/www.scientific.net/ssp.155.71.
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We study electron transport properties of some molecular wires and a unconventional disordered thin film within the tight-binding framework using Green's function technique. We show that electron transport is significantly affected by quantum interference of electronic wave functions, molecule-to-electrode coupling strengths, length of the molecular wire and disorder strength. Our model calculations provide a physical insight to the behavior of electron conduction across a bridge system.
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HWANG, J. R., M. F. TAI, H. C. KU, W. N. WANG i K. H. LII. "TRANSPORT PROPERTIES OF THE RARE EARTH DISORDERED SYSTEMS (R1−xYbx)Ba2Cu3O7 (R = Y, Sm)". International Journal of Modern Physics B 02, nr 06 (grudzień 1988): 1395–98. http://dx.doi.org/10.1142/s0217979288001219.
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Electrical and magnetic measurements have been carried out for the rare earth disordered superconducting copper oxide systems ( Y 1−x Yb x) Ba 2 Cu 3 O 7 (substitution with large rare earth mass difference) and ( Sm 1−x Yb x) Ba 2 Cu 3 O 7 (substitution with large rare earth ionic size difference). Effect of compositional variation upon room temperature electrical resistivity shows no disorder scattering contribution from the randomly distributed rare earth ions located on the (1/2, 1/2, 1/2) site of the space group Pmmm. This result indicates very low conduction electron density of states surrounding rare earth ions. On the contrary, negative deviation of electrical resistivity from the linear Vegard law was observed. This reduced conduction electron scattering was discussed through the variation of packing density, grain size and/or twin structure.
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Rezania, Hamed. "Electronic properties of disordered zigzag carbon nanotubes". International Journal of Modern Physics B 29, nr 05 (20.02.2015): 1550020. http://dx.doi.org/10.1142/s0217979215500204.
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We study the density of states of zigzag carbon nanotube (CNT) doped with both Boron and nitrogen atoms as donor and acceptor impurities, respectively. The effect of scattering of the electrons on the electronic spectrum of the system can be obtained via adding random on-site energy term to the tight binding model Hamiltonian which describes the clean system. Green's function approach has been implemented to find the behavior of electronic density. Due to Boron (Nitrogen) doping, Fermi surface tends to the valence (conduction) band of semiconductor CNT so that the energy gap width reduces. Furthermore the density of states of disordered metallic zigzag CNTs includes a peak near the Fermi energy.
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Hoon Lee, Chang, Dong Keun Oh i Cheol Eui Lee. "Electron Paramagnetic Resonance Observation of Critical Behaviors in a Disordered Conducting Polymer System". Journal of the Physical Society of Japan 72, nr 7 (15.07.2003): 1812–13. http://dx.doi.org/10.1143/jpsj.72.1812.
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Bergmann, Gerd. "WEAK LOCALIZATION AND ITS APPLICATIONS AS AN EXPERIMENTAL TOOL". International Journal of Modern Physics B 24, nr 12n13 (20.05.2010): 2015–52. http://dx.doi.org/10.1142/s021797921006468x.
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The resistance of two-dimensional electron systems such as thin disordered films shows deviations from Boltzmann theory, which are caused by quantum corrections and are called weak localization. The theoretical origin of weak localization is the Langer–Neal graph in Kubo formalism. It represents an interference experiment with conduction electrons split into pairs of waves interfering in the back-scattering direction. The intensity of the interference (integrated over the time) can easily be measured by the resistance of the film. The application of a magnetic field B destroys the phase coherence after a time which is proportional to 1/B. For a field of 1 T this time is of the order of 1 ps. Therefore with a dc experiment, one can measure characteristic times of the electron system in the range of picoseconds. Weak localization has been applied to measure dephasing, spin-orbit scattering, tunneling times, etc. One important field of application is the investigation of magnetic systems and magnetic impurities by measuring the magnetic dephasing time and its temperature dependence. Here the Kondo maximum of spin-flip scattering, spin-fluctuations, Fermi liquid behavior and magnetic d-resonances have been investigated. Another field is the detection of magnetic moments for very dilute alloys and surface impurities. This article given a brief survey of different applications of weak localization with a focus on magnetic impurities.
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RAVOT, D., O. GOROCHOV i A. MAUGER. "METAL-INSULATOR TRANSITION IN Yb1–x Gdx Te". International Journal of Modern Physics B 07, nr 01n03 (styczeń 1993): 814–17. http://dx.doi.org/10.1142/s0217979293001724.
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The metal-insulator transition of Yb1−xGdxTe has been studied by tuning x, since Gd3+ions act as donors. Transport and magnetic properties have been measured for 0<x<1 and T≥4.2K. For x>0.5, the material is a metallic antiferromagnet with a Néel temperature decreasing with x. An outstanding T–1 behavior of the resistivity is observed in a broad temperature range, which we attribute to electron-electron scattering in 3D dimension disordered systems. This behavior is observed in the metallic side, for x in the range 0.2<x≤0.5, and it can be regarded as a pretransition effect to the weak localization regime. This feature gives evidence that localization occurs because random fluctuations are enhanced by the magnetic interaction of the conduction electrons with Gd3+ ions favoring the formation of magnetic polarons. Only for x=0.2 can we observe an activated regime of the resistivity curve with a small activation energy ( ≈ 60K) typical of a thermal activation of the carriers above a mobility edge.
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Lau, Lik Nguong, Kean Pah Lim, Amirah Natasha Ishak, Mohd Mustafa Awang Kechik, Soo Kien Chen, Noor Baa’yah Ibrahim, Muralidhar Miryala, Masato Murakami i Abdul Halim Shaari. "The Physical Properties of Submicron and Nano-Grained La0.7Sr0.3MnO3 and Nd0.7Sr0.3MnO3 Synthesised by Sol–Gel and Solid-State Reaction Methods". Coatings 11, nr 3 (22.03.2021): 361. http://dx.doi.org/10.3390/coatings11030361.
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La0.7Sr0.3MnO3 (LSMO) and Nd0.7Sr0.3MnO3 (NSMO) possess excellent colossal magnetoresistance (CMR). However, research work on the neodymium-based system is limited to date. A comparative study between LSMO and NSMO prepared by sol–gel and solid-state reaction methods was undertaken to assess their structural, microstructural, magnetic, electrical, and magneto-transport properties. X-ray diffraction and structure refinement showed the formation of a single-phase composition. Sol–gel-synthesised NSMO was revealed to be a sample with single crystallite grains and exhibited intriguing magnetic and electrical transport behaviours. Magnetic characterisation highlighted that Curie temperature (TC) decreases with the grain size. Strong suppression of the metal–insulator transition temperature (TMI) was observed and attributed to the magnetically disordered grain surface and distortion of the MnO6 octahedra. The electrical resistivity in the metallic region was fitted with theoretical models, and the conduction mechanism could be explained by the grain/domain boundary, electron–electron, and electron–magnon scattering process. The increase in the scattering process was ascribed to the morphology changes. Enhancement of low-field magnetoresistance (LFMR) was observed in nano-grained samples. The obtained results show that the grain size and its distribution, as well as the crystallite formation, strongly affect the physical properties of hole-doped manganites.
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Luo, Yongkang, F. Ronning, N. Wakeham, Xin Lu, Tuson Park, Z. A. Xu i J. D. Thompson. "Pressure-tuned quantum criticality in the antiferromagnetic Kondo semimetal CeNi2−δAs2". Proceedings of the National Academy of Sciences 112, nr 44 (19.10.2015): 13520–24. http://dx.doi.org/10.1073/pnas.1509581112.
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The easily tuned balance among competing interactions in Kondo-lattice metals allows access to a zero-temperature, continuous transition between magnetically ordered and disordered phases, a quantum-critical point (QCP). Indeed, these highly correlated electron materials are prototypes for discovering and exploring quantum-critical states. Theoretical models proposed to account for the strange thermodynamic and electrical transport properties that emerge around the QCP of a Kondo lattice assume the presence of an indefinitely large number of itinerant charge carriers. Here, we report a systematic transport and thermodynamic investigation of the Kondo-lattice system CeNi2−δAs2 (δ ≈ 0.28) as its antiferromagnetic order is tuned by pressure and magnetic field to zero-temperature boundaries. These experiments show that the very small but finite carrier density of ∼0.032 e−/formular unit in CeNi2−δAs2 leads to unexpected transport signatures of quantum criticality and the delayed development of a fully coherent Kondo-lattice state with decreasing temperature. The small carrier density and associated semimetallicity of this Kondo-lattice material favor an unconventional, local-moment type of quantum criticality and raises the specter of the Nozières exhaustion idea that an insufficient number of conduction-electron spins to separately screen local moments requires collective Kondo screening.
Rozprawy doktorskie na temat "Electron Conduction - Disordered System"
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Shrestha, Kiran (Engineer). "Electrical Conduction Mechanisms in the Disordered Material System P-type Hydrogenated Amorphous Silicon". Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700106/.
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The electrical and optical properties of boron doped hydrogenated amorphous silicon thin films (a-Si) were investigated to determine the effect of boron and hydrogen incorporation on carrier transport. The a-Si thin films were grown by plasma enhanced chemical vapor deposition (PECVD) at various boron concentrations, hydrogen dilutions, and at differing growth temperatures. The temperature dependent conductivity generally follows the hopping conduction model. Above a critical temperature, the dominant conduction mechanism is Mott variable range hopping conductivity (M-VRH), where p = ¼, and the carrier hopping depends on energy. However, at lower temperatures, the coulomb interaction between charge carriers becomes important and Efros-Shklosvkii variable hopping (ES-VRH) conduction, where p=1/2, must be included to describe the total conductivity. To correlate changes in electrical conductivity to changes in the local crystalline order, the transverse optical (TO) and transverse acoustic (TA) modes of the Raman spectra were studied to relate changes in short- and mid-range order to the effects of growth temperature, boron, and hydrogen incorporation. With an increase of hydrogen and/or growth temperature, both short and mid-range order improve, whereas the addition of boron results in the degradation of short range order. It is seen that there is a direct correlation between the electrical conductivity and changes in the short and mid-range order resulting from the passivation of defects by hydrogen and the creation of trap states by boron. This work was done under the ARO grant W911NF-10-1-0410, William W. Clark Program Manager. The samples were provided by L-3 Communications.
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Merkt, Rainer. "Density of states and delocalization in low dimensional disordered electron systems". [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960264817.
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Kneten, Kristin Renae. "Effects of redox system structure on electron transfer kinetics at ordered graphite and disordered carbon electrodes /". The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487848078450307.
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Sayad, Mohammad [Verfasser], i Michael [Akademischer Betreuer] Potthoff. "Real-time dynamics of spins coupled to a conduction-electron system / Mohammad Sayad ; Betreuer: Michael Potthoff". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2017. http://d-nb.info/113326218X/34.
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Araki, Moto. "Steplike electric conduction in a classical two-dimensional electron system through a narrow constriction in a microchannel". 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175099.
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Langenfeld, Annette. "Etude de corrélations électroniques dans des systèmes désordonnés". Grenoble 1, 1993. http://www.theses.fr/1993GRE10081.
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Cette these est faite de deux parties independantes. La premiere partie traite les corrections quantiques a l'effet hall anormal. On peut montrer que les termes de l'anomalie coulombienne se compensent mutuellement en considerant la diffusion asymetrique des electrons de conduction par les moments magnetiques d'une couche metallique desordonnee. La contribution venant de la localisation faible est coupee par la diffusion asymetrique qui brise la coherence de phase. Les resultats sont en bon accord avec une experience recente sur des couches minces de fer desordonnees et ferromagnetiques. Dans la seconde partie, on etudie la formation de moments magnetiques localises dans des systemes comme des semiconducteurs dopes en phase metallique. Le calcul est base sur le modele de hubbard avec desordre hors-diagonal. En examinant le modele a une seule impurete faiblement rattachee au reseau, on trouve un moment magnetique localise, et cela meme dans l'approximation de hartree-fock pour la repulsion locale u. On associe a ce moment magnetique un effet kondo dont la nature et la dependance par rapport au desordre sont discutees. Les resultats sont compares a une experience recente mesurant le pouvoir thermoelectrique du si:p. La correspondance est satisfaisante
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Forestier, Guillaume. "Transport quantique dans les verres de spins". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY023/document.
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Les travaux expérimentaux présentés dans cette thèse associent deux pans de la physique de la matière condensée, avec d'un côté la physique des verres de spins et de l'autre la physique mésoscopique. Le verre de spins est un exemple emblématique de système désordonné et frustré, il se caractérise à basse température par un ordre magnétique non conventionnel, où le désordre magnétique apparaît gelé. De plus, celui-ci est considéré comme un système modèle pour étudier les verres en général et de ce fait, il a fait l'objet de nombreuses études expérimentales et théoriques. Après d'importants efforts de recherche, la description de l'état fondamental de ce système a abouti à deux approches très différentes. La première, donnée par la résolution non triviale du problème en champ moyen, met en avant un état fondamental composé d'une multitude d'états organisés et hiérarchisés. La deuxième approche, dite des "gouttelettes", se base quant à elle sur la dynamique hors équilibre d'un unique état. Cependant, en dépit de ces contributions, la compréhension de cette phase est loin d'être complète et la nature de l'état fondamental reste encore un débat ouvert. Dans un conducteur mésoscopique, le transport se fait de manière cohérente : les électrons gardent la mémoire de leur phase, ce qui permet d'observer des effets d'interférences électroniques. La motivation à la base de ce travail est d'utiliser ces effets d'interférences comme outil pour étudier le verre de spins. En effet, étant donné que les interférences électroniques dépendent intiment de la disposition du désordre statique du conducteur, le transport cohérent peut se révéler être une sonde microscopique très efficace pour étudier la configuration du désordre dans un conducteur. Bien que quelques expériences pionnières de transport cohérent existent dans des verres de spins, ce domaine de recherche n'a que très peu été exploré. Néanmoins, il a connu un récent renouveau grâce à des travaux théoriques qui montrent de quelle manière cette sonde est sensible au désordre magnétique gelé et comment elle peut fournir des informations sur la nature de l'état fondamental du verre de spins. Ainsi, ce travail de thèse expérimental présente l'implémentation de mesure de transport dans des verres de spins mésoscopiques. La première partie de l'étude est consacrée aux caractéristiques générales de transport classique et quantique de ces systèmes. Nous avons examiné les propriétés de la résistivité en fonction de la température et du champ magnétique et nous montrons que ces systèmes mésoscopiques possèdent bien des comportements attendus pour des verres de spins. Dans une deuxième partie, nous nous sommes intéressés au comportement de la magnétorésistance à bas. Nous avons mis en avant que celle-ci présente une forte hystérésis dont l'amplitude dépend fortement, de la température dans la phase vitreuse et de la vitesse de balayage du champ magnétique. Nous avons argumenté que ce comportement particulier traduit la mise hors équilibre du système et montrons comment la température et la vitesse de balayage du champ magnétique pilotent l'écart à l'équilibre. Dans cette partie, nous avons aussi examiné par des mesures de transport la relaxation du système vers l'équilibre, après l'avoir excité. Nous présentons également les propriétés de transport étonnantes que nous avons observées à bas champ, résultant de protocoles en températures et en champs magnétiques plus complexesThe experiments presented in this thesis associate two fields of condensed matter physic, on the one hand with the spin glass physic and the other hand with the mesoscopic physic. The spin glass state is one of the most emblematic of disordered and frustred system and at low temperature, it is caracterized by an unconventionel order where the magnetic disorder is quenched. Moroever, it is considered as a model system for glasses in general and thereby it has been extensively studied, both experimentally and theoreticlly. After extensive research efforts, the description of fundamental state of the system has lead towards two well different approaches. The first, given by the mean field solution, highlights a fundamental composed of mulitple states organised and hierarchical. The second, called droplet model is based on the off--equilibrium dynamic of a unique ground state. However, despite these contributions, the understanding ot this phase is far from being complete and the nature of the ground state still remains an open question. In a mesoscopic conductor, the transport of electron is coherent: electrons keep the memory of their phase, so that one can observe interference effects. The main motivation of this work is to use these interference effects in order to to probe the spin glass state. Indeed, as electronic interference depends of the position of the static disorder, coherent transport can be a useful tool to study the configuration of the microscopic disorder. Althought few coherent transport experiments exist to probe the spin glass, this field of research has very little explored. Nevertheless, this area has been a revival thanks to theoritical work, showing how coherent transport is sensitived to the quenched disorder and how it may provide informations of the nature of fundamental state of spin glass. So, this experimental work deals with the implementation of transport measurements in mesoscopic spin glasses. The first part of the study is focused on the general charateristics of classical and quatum transport of these system. We have examined the resistivity as a function of the temperature and magnetic field and we show that these mesoscopic systems have a spin glass-like behaviour. In a second part, we have focused on the low field magnetoresistivity. We show that it presents a strong hysteresis, whose the amplitude is strongly depends, both of the temperature in the glassy phase and sweeping rate of the magnetic field. We argue that this particular behaviour is related to the out off-equilibrium of the system and we show how the temperature and the sweeping rate control the deviation to the equilibrium. In this part, we also examine by transport measurements how the system relaxes towards the equilibrium just after its excitation. In addition, we present surprinsing transport propreties that we observed, resulting of experimental protocols more sophisticated in temperatures and magnetic fields
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Akkermans, Éric. "Propagation d'ondes dans les milieux désordonnés". Grenoble 1, 1986. http://www.theses.fr/1986GRE10050.
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Les phenomenes etudies font intervenir la phase de l'onde et la dimensionalite de l'espace de propagation. Dans le cas des systemes uni et bidimensionnels, les ondes subissant des collisions multiples elastiques interferent fortement et conduisent a des modes propres exponentiellement localises. Leur structure est etudiee sur la base d'un modele particulier de potentiel incommensurable. Le transport des phonons et des electrons dans les systemes unidimensionnels desordonnes a ete plus generalement caracterise
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Brötzmann, Marc. "Electrical characterization of Metal - Amorphous Semiconductor - Semiconductor diodes – a general conduction model". Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0019-E60D-D.
Pełny tekst źródłaKsiążki na temat "Electron Conduction - Disordered System"
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Davey, Kent. Magnetic field stimulation: the brain as a conductor. Redaktorzy Charles M. Epstein, Eric M. Wassermann i Ulf Ziemann. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780198568926.013.0005.
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For the purposes of magnetic stimulation, the brain can be treated as a homogeneous conductor. A properly designed brain stimulation system starts with the target stimulation depth, and it should incorporate the neural strength–duration response characteristics. Higher-frequency pulses require stronger electric fields. The background of this article is the theoretical base determining, where in the brain TMS induces electrical activity, and whether this shifts as a function of differences in the conductivity and organization of gray matter, white matter, and cerebrospinal fluid. The use of strong electric fields to treat many neurological disorders is well established. Both in the treatment of incontinence and clinical depression, the electric field should be sufficiently strong to initiate an action potential. The frequency, system voltage, capacitance, core stimulator size, and number of turns are treated as unknowns in a TMS stimulation design. This article presents the possible topological changes to be considered in the future.
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Brady, Peter A. Evaluation and Treatment of Arrhythmias. Oxford University Press, 2012. http://dx.doi.org/10.1093/med/9780199755691.003.0043.
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Abnormal cardiac arrhythmias may be due to reentry, abnormal automaticity, or triggered activity. Reentrant rhythms may be microreentrant or macroreentrant. Ambulatory (Holter) monitoring is useful for the evaluation of both symptomatic and asymptomatic rhythm disturbances and their relationship to daily activity. Treadmill exercise testing is very useful in the evaluation of patients who present with bradycardia and symptoms of palpitations because it allows both documentation of the adequacy of heart rate response to exercise and the recording of the cardiac rhythm during exercise in a controlled setting with ECG monitoring. An electrophysiologic study is useful for assessing sinus node function and the cardiac conduction system and for attempting to induce atrial or ventricular arrhythmias that could explain the clinical presentation. Electrophysiologic study requires placement of electrode catheters in the heart to record and to stimulate heart rhythm. Several therapeutic options are available for heart rhythm disorders, including drug therapy, radiofrequency ablation, and device therapy.
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Shaibani, Aziz. Pseudoneurologic Syndromes. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190661304.003.0022.
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The term functional has almost replaced psychogenic in the neuromuscular literature for two reasons. It implies a disturbance of function, not structural damage; therefore, it defies laboratory testing such as MRIS, electromyography (EMG), and nerve conduction study (NCS). It is convenient to draw a parallel to the patients between migraine and brain tumors, as both cause headache, but brain MRI is negative in the former without minimizing the suffering of the patient. It is a “software” and not a “hardware” problem. It avoids irritating the patient by misunderstanding the word psychogenic which to many means “madness.”The cause of this functional impairment may fall into one of the following categories:• Conversion reaction: conversion of psychological stress to physical symptoms. This may include paralysis, hemisensory or distal sensory loss, or conversion spasms. It affects younger age groups.• Somatization: chronic multiple physical and cognitive symptoms due to chronic stress. It affects older age groups.• Factions disorder: induced real physical symptoms due to the need to be cared for, such as injecting oneself with insulin to produce hypoglycemia.• Hypochondriasis: overconcern about body functions such as suspicion of ALS due to the presence of rare fasciclutations that are normal during stress and after ingestion of a large amount of coffee. Medical students in particular are targets for this disorder.The following points are to be made on this topic. FNMD should be diagnosed by neuromuscular specialists who are trained to recognize actual syndrome whether typical or atypical. Presentations that fall out of the recognition pattern of a neuromuscular specialist, after the investigations are negative, they should be considered as FNMDs. Sometimes serial examinations are useful to confirm this suspicion. Psychatrists or psychologists are to be consulted to formulate a plan to discover the underlying stress and to treat any associated psychiatric disorder or psychological aberration. Most patients think that they are stressed due to the illness and they fail to connect the neuromuscular manifestations and the underlying stress. They offer shop around due to lack of satisfaction, especially those with somatization disorders. Some patients learn how to imitate certain conditions well, and they can deceive health care professionals. EMG and NCS are invaluable in revealing FNMD. A normal needle EMG of a weak muscles mostly indicates a central etiology (organic or functional). Normal sensory responses of a severely numb limb mean that a lesion is preganglionic (like roots avulsion, CISP, etc.) or the cause is central (a doral column lesion or functional). Management of FNMD is difficult, and many patients end up being chronic cases that wander into clinics and hospitals seeking solutions and exhausting the health care system with unnecessary expenses.It is time for these disorders to be studied in detail and be classified and have criteria set for their diagnosis so that they will not remain diagnosed only by exclusion. This chapter will describe some examples of these disorders. A video clip can tell the story better than many pages of writing. Improvement of digital cameras and electronic media has improved the diagnosis of these conditions, and it is advisable that patients record some of their symptoms when they happen. It is not uncommon for some Neuromuscular disorders (NMDs), such as myasthenia gravis (MG), small fiber neuropathy, and CISP, to be diagnosed as functional due to the lack of solid physical findings during the time of the examination. Therefore, a neuromuscular evaluation is important before these disorders are labeled as such. Some patients have genuine NMDs, but the majority of their symptoms are related to what Joseph Marsden called “sickness behavior.” A patient with carpal tunnel syndrome (CTS) may unconsciously develop numbness of the entire side of the body because he thinks that he may have a stroke.
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Saitoh, E., i K. Ando. Experimental observation of the spin Hall effect using spin dynamics. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198787075.003.0015.
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This chapter describes an experiment on the inverse spin Hall effect (ISHE) induced by spin pumping. Spin pumping is the generation of spin currents as a result of magnetization M(t) precession; in a ferromagnetic/paramagnetic bilayer system, a conduction-electron spin current is pumped out of the ferromagnetic layer into the paramagnetic conduction layer in a ferromagnetic resonance condition. The sample used in the experiment is a Ni81Fe19/Pt bilayer film comprising a 10-nm-thick ferromagnetic Ni81Fe19layer and a 10-nm-thick paramagnetic Pt layer. For the measurement, the sample system is placed near the centre of a TE011 microwave cavity at which the magnetic-field component of the microwave mode is maximized while the electric-field component is minimized.
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Kimura, T. Introduction of spin torques. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198787075.003.0019.
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This chapter discusses the spin-transfer effect, which is described as the transfer of the spin angular momentum between the conduction electrons and the magnetization of the ferromagnet that occurs due to the conservation of the spin angular momentum. L. Berger, who introduced the concept in 1984, considered the exchange interaction between the conduction electron and the localized magnetic moment, and predicted that a magnetic domain wall can be moved by flowing the spin current. The spin-transfer effect was brought into the limelight by the progress in microfabrication techniques and the discovery of the giant magnetoresistance effect in magnetic multilayers. Berger, at the same time, separately studied the spin-transfer torque in a system similar to Slonczewski’s magnetic multilayered system and predicted spontaneous magnetization precession.
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Horing, Norman J. Morgenstern. Quantum Statistical Field Theory. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198791942.001.0001.
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The methods of coupled quantum field theory, which had great initial success in relativistic elementary particle physics and have subsequently played a major role in the extensive development of non-relativistic quantum many-particle theory and condensed matter physics, are at the core of this book. As an introduction to the subject, this presentation is intended to facilitate delivery of the material in an easily digestible form to students at a relatively early stage of their scientific development, specifically advanced undergraduates (rather than second or third year graduate students), who are mathematically strong physics majors. The mechanism to accomplish this is the early introduction of variational calculus with particle sources and the Schwinger Action Principle, accompanied by Green’s functions, and, in addition, a brief derivation of quantum mechanical ensemble theory introducing statistical thermodynamics. Important achievements of the theory in condensed matter and quantum statistical physics are reviewed in detail to help develop research capability. These include the derivation of coupled field Green’s function equations of motion for a model electron-hole-phonon system, extensive discussions of retarded, thermodynamic and non-equilibrium Green’s functions, and their associated spectral representations and approximation procedures. Phenomenology emerging in these discussions includes quantum plasma dynamic, nonlocal screening, plasmons, polaritons, linear electromagnetic response, excitons, polarons, phonons, magnetic Landau quantization, van der Waals interactions, chemisorption, etc. Considerable attention is also given to low-dimensional and nanostructured systems, including quantum wells, wires, dots and superlattices, as well as materials having exceptional conduction properties such as superconductors, superfluids and graphene.
Części książek na temat "Electron Conduction - Disordered System"
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Wada, Y. "Doping and Disorder in Conducting Polymers". W New Horizons in Low-Dimensional Electron Systems, 415–32. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-3190-2_27.
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Oka, T., i H. Aoki. "Nonequilibrium Quantum Breakdown in a Strongly Correlated Electron System". W Quantum and Semi-classical Percolation and Breakdown in Disordered Solids, 1–35. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-85428-9_9.
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"4. Electron states and charge transport in disordered systems". W Hopping Conduction in Solids, 88–104. De Gruyter, 1985. http://dx.doi.org/10.1515/9783112618189-005.
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GOR'KOV, LEV P. "Disorder and Interactions in the System of Quasi One-dimensional Electrons". W Electron–Electron Interactions in Disordered Systems, 619–69. Elsevier, 1985. http://dx.doi.org/10.1016/b978-0-444-86916-6.50014-4.
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MOTT, N. F. "Conduction in Non-crystalline Systems I. Localized Electronic States in Disordered Systems". W World Scientific Series in 20th Century Physics, 429–39. WORLD SCIENTIFIC, 1995. http://dx.doi.org/10.1142/9789812794086_0024.
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Cecilia Vega-Corredor, Maria, Simon Hoermann, Alison Watkins i Melanie Tomintz. "Design Insights to Support the Development of Effective Virtual Reality Nicotine and Vaping Dependency Therapy Scenarios for Future Telehealth". W Biomedical Engineering. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106958.
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Vaping, or the use of electronic nicotine delivery systems (ENDS), has grown rapidly worldwide and is becoming an epidemic among youth in many countries. Invented as a method to help to quit smoking, ENDS are very popular, reaching increasing numbers of users and becoming a health concern. Virtual reality technology (VRT) represents an important tool for conducting addiction-associated interventions, including telemedicine. The design and quality of virtual reality scenarios (VRS) used for VR interventions are fundamental. How well VRS can replicate real-world scenarios has an impact on how realistic the VR immersion experiences are. Thus, VRS development influences therapeutic outcomes. VRT is used for interventions and treatments for smoking-related nicotine addiction but has yet to be validated for vaping-related disorders. Since vaping represents a technological step forward in nicotine consumption, the accurate contextualization of environments surrounding vapers is fundamental for developing advanced VR tools for the prevention and treatment of vaping disorders. Here, we present the results of focus group discussion with young vapers in New Zealand. The knowledge gained from this study will be used to design VRS for cue exposure and reactivity as a first step toward developing effective solutions for vaping disorders using VR interventions and telemedicine.
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Schroeder, Daniel V. "Quantum Statistics". W An Introduction to Thermal Physics, 257–326. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192895547.003.0007.
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This chapter begins by extending the Boltzmann distribution to the case of a system that exchanges particles with its environment. This idea finds direct applications ranging from hemoglobin adsorption to ionization of atoms in stars. But the main applications are to dense “gases” in which the quantum behavior of identical particles comes into play. Examples include conduction electrons in metals and semiconductors; white dwarf and neutron stars; photon gases and thermal radiation from incandescent objects; neutrino and electron-positron production in the early universe; quasiparticles associated with vibrations and magnetic excitations in solids; and Bose-Einstein condensation of ultracold clouds of atoms.
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Kwaśnicki, Paweł. "Quantum Dots as Material for Efficient Energy Harvesting". W Quantum Dots - Recent Advances, New Perspectives and Contemporary Applications [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106579.
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The essence of the photovoltaic effect is the generation of electric current with the help of light. Absorption of a quantum of the energy of light (photon) generates the appearance of an electron in the conduction band and holes in the valence band. The illumination of the material, in general, is not uniform, which leads to the appearance of spatially inhomogeneous charge in the band valence and conductivity. Besides, electrons and holes generally diffuse with different velocities, which leads to the creation of a separated space charge and generation of an electric field (sometimes called the Dember field). This field inhibits further separation of cargo. The reverse processes also take place in the system, i.e. electron recombination and holes. These processes are destructive from the point of view of photovoltaics and should be minimized, which is achieved; thanks to the spatial separation of electrons and holes. The point is that electrons and holes were carried away from the area where they formed as quickly as possible, yes to prevent their spontaneous recombination. The use of semiconductor quantum dots introduced into the photoelectric material is currently a very important and effective way to increase the efficiency of photoelectric devices and photovoltaic cells. This is due to the fact that in semiconductor photoelectric materials with no quantum dots, there is always some upper limit of the wavelength λgrgr≃1,24/EgeV for absorbed light, above which the light is not absorbed.
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Murali Manoj, Kelath, Nikolai Bazhin, Yanyou Wu i Afsal Manekkathodi. "Murburn Model of Photosynthesis: Effect of Additives like Chloride and Bicarbonate". W Chlorophylls [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.103132.
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Oxygenic photosynthesis essentially involves photo-lysis (splitting of water to release oxygen), photo-reduction (formation of NADPH), and photo-phosphorylation (synthesis of ATP) reactions. These reactions use photoactive pigments such as chlorophylls and carotenoids. Z-scheme and Kok-Joliot cycle, the acclaimed and deterministic model of photosynthesis, are founded on the classical enzyme reaction mechanisms that depend solely on affinity-based interactions of enzymes with the substrates at defined active sites, for explaining electron/moiety transfers. In contrast, the new murburn model is built on stochastic collisions between diffusible reactive species (DRS) and other milieu components (including enzymes, substrates and ions). This novel perspective explains fast kinetics and action spectrum, and affords a spontaneously probable/evolvable biochemical system. The murburn perspective proposes that the photo-excitation of pigments in the chloroplast leads to effective charge separation and DRS-formation. DRS are stabilized/utilized by a pool of redox-active components via disordered/parallel bimolecular interactions at the thylakoid membrane interface. Herein, we provide details of how murburn model is a thermodynamically, kinetically, and mechanistically viable mechanism for the formation of ATP, NADPH and oxygen. The murburn model also provides more viable explanations for several classical experimental observations in photosynthesis (Emerson enhancement effect, Jagendorf/Racker experiments, etc.) and the non-specific effects of diverse additives (such as chloride and bicarbonate).
Streszczenia konferencji na temat "Electron Conduction - Disordered System"
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Samuel, B. A., C. M. Lentz i M. A. Haque. "Experimental Study of Structure-Electrical Transport Correlation in Single Disordered Carbon Nanowires". W ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11739.
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We present experimental results characterizing the changes in electrical transport of single disordered carbon nanowires (diameter 150–250 nm) to the changes in microstructure within the nanowires induced by synthesis temperature. The material system studied is a nanoporous, semiconducting disordered carbon nanowire obtained from the pyrolysis of a polymeric precursor (polyfurfuryl alcohol). Unlike the other allotropes of carbon such as diamond, graphite (graphenes) and fullerenes (CNT, buckyballs), disordered carbons lack crystalline order and hence can exhibit a range of electronic properties, dependent on the degree of disorder and the local microstructure. Such disordered carbon nanowires are therefore materials whose electronic properties can be engineered to specifications if we understand the structure-property correlations. Using dark DC conductivity tests, measurements were performed from 300K to 450K. The charge transport behavior in the nanowires is found to follow an activation-energy based conduction at high temperatures. The conductivity for nanowires synthesized from 600°C to 2000°C is calculated and is linked to changes in the microstructure using data obtained from SEM, TEM and Raman spectroscopy. The electrical properties of the nanowire are shown to be linked intrinsically to the microstructure and the degree of disorder, which in turn can be controlled to a great extent just by controlling the pyrolysis temperature. This ability to tune the electrical property, specifically conductivity, and map it to the structural changes within the disordered material makes it a candidate material for use in active/passive electronic components, and as versatile transducers for sensors.
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Saeta, P. N., J. K. Wang, Y. Siegal, N. Bloembergen i E. Mazur. "Femtosecond, Electronically-Induced Disordering of GaAs". W International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/up.1992.mc8.
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Picosecond laser pulse experiments on semiconductors show that a thermal melting model can explain the behavior of these materials when irradiated with such pulses.1 This model assumes that energy is quickly transferred from the electrons excited by the laser pulse to the lattice through phonon emission. The lattice then heats up to the melting temperature and undergoes a phase transition to the liquid phase. However, the thermal model breaks down if the energy of the laser pulse is deposited into the electronic system on a time scale which is short compared to the electron-lattice energy relaxation time, as in the case of femtosecond laser pulses exciting semiconductors with relaxation times of a few picoseconds.2 In this case, the bond breaking which occurs through excitation of valence electrons to the conduction band can lead directly to ionic disordering while the lattice is still cold.3 Experiments performed on silicon with femtosecond laser pulses indeed suggest disordering of a cold lattice.4 We have performed a series of measurements on GaAs using 160-fs pulses which show that above a threshold pump fluence of 0.1 J/cm2, the material undergoes an ultrafast transition to a disordered, metallic phase in less than 0.5 ps.
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Krauß, J., T. Kippenberg, P. Kiesel, G. H. Döhler, E. Greger, H. P. Schweizer i M. Moser. "Polarization threshold switches based on ordered GaInP". W The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/cleo_europe.1998.ctul3.
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The material system (Al) GaInP is very interesting for opto-electronic devices in the visible spectral range. Under suitable growth conditions (Al)GaInP epitaxial layers show a spontaneous self ordering of the CuPtB-type [1]. For growth in the [100]-direction this ordering results in alternating Ga-rich and In-rich {111}B planes. The mono-atomic superlattice causes significant changes of the electronic structure compared to the normal disordered alloy. In particular, ordered crystals exhibit a band gap reduction and a valence band splitting at the T-point. As a consequence of dipole selection rules, transitions between the highest valence band and the conduction band are forbidden for light polarized parallel to the ordering direction. This leads to a strong polarization anisotropy even for light propagating normal to the {100} crystal surface.
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Hopkins, Patrick E. "Contribution of D-Band Electrons to Ballistic Electron Transport and Interfacial Scattering During Electron-Phonon Nonequilibrium in Thin Metal Films". W ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88270.
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Electron-interface scattering during electron-phonon nonequilibrium in thin films creates another pathway for electron system energy loss as characteristic lengths of thin films continue to decrease. As power densities in nanodevices increase, excitations of electrons from sub-conduction-band energy levels will become more probable. These sub-conduction-band electronic excitations significantly affect the material’s thermophysical properties. In this work, the effects of d-band electronic excitations are considered in electron energy transfer processes in thin metal films. In thin films with thicknesses less than the electron mean free path, ballistic electron transport leads to electron-interface scattering. The ballistic component of electron transport, leading to electron-interface scattering, is studied by a ballistic-diffusive approximation of the Boltzmann Transport Equation. The effects of d-band excitations on electron-interface energy transfer is analyzed during electron-phonon nonequilibrium after short pulsed laser heating in thin films.
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Kash, J. A., J. C. Tsang i J. Hvam. "Sub-picosecond Raman Spectroscopy of Electron - LO Phonon Dynamics in GaAs". W Picosecond Electronics and Optoelectronics. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/peo.1985.wc5.
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Highly excited ("hot") conduction band electrons in GaAs lose their energy primarily by the emission of zone center LO phonons1. The quantitative study of this emission process requires the ability to measure the vibrational spectrum of GaAs on a sub-picosecond time scale. We have combined a sync-pumped dye laser with a filtered fiber optic pulse compressor to obtain spectrally clean 600 femtosecond pulses for wavelengths between 580 nm and 610 nm. A pump pulse generates excited carriers and a weaker, delayed probe pulse measures the Raman scattering from the phonons created by these carriers. Because the average probe beam power is of the order of 1 milliwatt and has a spectral full width at half maximum of about 30 cm-1, the weak Raman scattered spectrum is detected by a cooled, microchannel plate photomultiplier with a position sensitive resistive anode. Changes of less than 10% from the equilibrium room temperature phonon population can be observed using this system. Spectral shifts of the order of 10 cm-1 can be resolved.
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Wang, Haidong, Weigang Ma, Xing Zhang i Wei Wang. "Mass Nature of Heat and Its Applications IV: Thermal Wave and Periodic Temperature Oscillation in Metallic Films Heated by Ultra-Short Pulsed Lasers". W 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22368.
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The ultra-fast heat transfer in metallic films has attracted great interest in modern femtosecond laser processing and metallic film manufacturing. Considering the unphysical infinite propagation speed of heat disturbances based on Fourier’s model, some hyperbolic heat transfer models have been developed in the past decades, leading to the character of thermal wave in metallic films under ultra-fast laser heating conditions. In this paper the thermomass model is applied to obtain the governing equation for heat conduction in the thin films under pulsed laser heating, which is a damped wave equation and identical with that based on the Hyperbolic Two-Step (HTS) model. The semi-implicit Crank-Nicholson scheme is used to solve governing equations. Numerical results show that there may be two kinds of temperature oscillations existed in metallic films heated by ultra-short pulsed lasers, and the thermally oscillating boundary condition usually dominates over that caused by thermal wave induced oscillation of the electron temperature, which is validated by the measurement of the temperature response at the rear surface using a femtosecond laser pump-probe system. The measured electron temperature curve agrees well with the theoretically predicted one.
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Brown, J. Teye, Ajay M. Popat, Chad B. O’Neal i Yixiang Xie. "Intermetallic Effects of Electroplated Lead-Free Solder Bumps Using a Novel Single Chamber Electroplating Process for Large Diameter Wafers". W ASME 2007 InterPACK Conference collocated with the ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ipack2007-33906.
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In this study solder bumps of various alloys and less than 100 microns in diameter were electroplated using a novel single chamber electroplating process in which the plating baths are exchanged between the different metal plating layers. This equipment is new to the manufacturing arena. The reflow profile and process was then optimized for the various alloys such as SnAg, and electroplated layered SnPb, and PbSn 95/5%, with PbSn 95/5% being the control leaded solder for comparison. Various fluxes were also used during the reflow of these bumps. The solder bumps were reflowed on a conduction reflow oven in a nitrogen environment such that the temperature profile could be carefully controlled. The bumps were analyzed by examining the bump diameter and height uniformity, surface quality, and elemental composition and distribution inside the bumps. These analyses were done by visual inspection by optical microscopy, scanning electron microscopy, and electron dispersive spectroscopy (EDS). The wafers were diced near a row of solder bumps, then podded and polished using a metallographic polishing system to the center of solder bumps. These bump cross-sections were then examined by EDS to perform elemental mapping of the alloy constituents.
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Zah, C. E., R. Bhat i T. P. Lee. "High Temperature Uncooled Lasers". W Semiconductor Lasers: Advanced Devices and Applications. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/slada.1995.wa.2.
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An uncooled laser transmitter is cheaper and more reliable than a thermo-electrically cooled laser transmitter because of its simplicity in packaging. A low-cost, highly-reliable uncooled laser may have a strong influence on pushing fiber deployment closer to the home. For loop applications, the laser transmitter must operate reliably over the temperature range from -40 to 85°C. It is rather difficult to make high performance uncooled lasers in the long wavelength region (1.3-1.55 μm) using the conventional GaxIn1-xASyP1-y/InP materials system because the laser temperature performance suffers from Auger recombination in the low bandgap material and poor electron confinement resulting from the small conduction band offset (ΔEc=0.4ΔEg). We will discuss the design of uncooled lasers to minimize the changes in both threshold current and slope efficiency over the temperature range from -40 to 85 °C. To prevent carrier overflow under high-temperature operation, the electron confinement energy is increased by using the AlxGayIn1-x-yAs/InP materials system instead of the conventional GaxIn1-xASyP1-y/InP materials system. Experimental results of the AlxGayIn1-x-yAs/InP strained quantum well lasers show superior high temperature performances as discussed below.
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Brennan, Kevin. "Theoretical comparison of multiquantum well, staircase, and doped quantum well avalanche photodiodes". W OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/oam.1986.tub5.
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A comparison of the multiquantum well, staircase, and doped quantum well avalanche photodiodes is presented based on the calculated gain and excess noise factor. The gain is determined from the electron and hole ionization probabilities per stage derived from an ensemble Monte Carlo calculation. The Monte Carlo calculation is particularly well adapted to study impact ionization in APDs since it includes the full details of the conduction and valence bonds as well as collisional broadening. Various device geometries are examined (different layer widths, dopings, and overall effective field strength) among the three different device types. In each case an optimized structure, in terms of the overall gain and excess noise factor, is presented. The results for devices made from the GalnAs/AllnAs material system indicate that the doped quantum well device gives the largest gain at the lowest excess noise factor of the three device types.
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DePoy, D. M., R. J. Dziendziel, G. W. Charache, P. F. Baldasaro i B. C. Campbell. "Interference Filters for Thermophotovoltaic Applications". W Optical Interference Coatings. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/oic.1998.thc.5.
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Direct conversion of heat to electricity using Thermophotovoltaic (TPV) systems is attracting renewed attention due to recent advances on low bandgap (0.5-0.7 eV) III-V semiconductor materials and devices. TPV systems utilize the same principle of operation as solar cells. In particular, a heat source radiatively emits photons which are incident on a semiconductor TPV device. Photons with energy greater than the semiconductor bandgap, Eg (typically ranging from 0.50 eV to 0.73 eV for TPV devices), excite electrons from the valence band to the conduction band. The resultant electron-hole pairs are then collected by metal contacts and can power electrical loads. Photons with energy less than the semiconductor bandgap are parasitically absorbed as heat. In order to increase the efficiency of a TPV system, some form of spectral control is used to reflect photons with energy less than the semiconductor bandgap back to the radiator.