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Zhou, Kaichang. "Novel Electrowetting Display Devices." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1248958684.
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Reddick, William Michael. "Novel silicon tunnelling devices." Thesis, University of Cambridge, 1997. https://www.repository.cam.ac.uk/handle/1810/251612.
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Huminiuc, Teodor. "Novel antiferromagnets for spintronic devices." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/18864/.
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Spin electronic or spintronic devices which are used in hard disk drive (HDD) read heads are expected to replace the current silicon based transistor technology used in volatile memories. A prime example for the net advantage of employing spin rather than electric charge manipulation is found in the newly developed magnetic random access memory (MRAM) which is proposed as a replacement for the dynamic random access memory (DRAM) based on three terminal metal-oxide-semiconductor (MOS) devices. Besides the decrease of energy consumption by a factor three arising from manipulating electron angular momentum, the magnetic memories are non-volatile hence they do not require constant power to store information. This allows for additional energy saving due to data stability when the storage device is powered off.
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Emmerson, Gregory Daniel. "Novel direct UV written devices." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/42435/.
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This thesis reports a series of developments based on UV writing of novel waveguide structures. The first section is an investigation into the production of Direct UV-written channel waveguides on the perimeter of a cylindrical substrate. Cylindrical waveguides were produced using variants of the Modified Chemical Vapour Deposition (MCVD) and Flame Hydrolysis Deposition for the fabrication of thin films on either surface of the cylinder. Three layer, buried waveguide structures were produced using three techniques, and channel waveguides Directly UV-written into one of the samples. The second section concerns the simultaneous definition of channel waveguides and Bragg grating structures in planar substrates. This new process used two overlapped, tightly focused UV laser beams to generate a ~3μm writing spot with an interference pattern within the intensity profile. Translation of the writing spot with the power set to a continuous value averages out the effect of the interference pattern, defining channel waveguides. Modulation of the intensity of the writing spot in the fabrication process results in the definition of channel waveguides and Bragg gratings at the same time. The structure of the grating is defined by the precise motion and modulation of the writing spot, a function controlled by a computer and is not an absolute function of the interference pattern. Using this Direct Grating Writing technique, grating and channel structures were written into blank photosensitive 3-layer silica-on-silicon samples producing gratings with peak reflection intensities between OdB and >30dB. Bragg gratings with peak centre wavelength reflections spanning 488nm were written in a single fabrication run, all with equalised grating strengths. Direct Grating Writing was also used to produce a range of 2-dimensional planar structures including y-splitters and directional couplers. The gratings produced using this new technique were used to investigate sample photosensitivity and waveguide dispersion. Other results include; superimposed gratings, the superposition of a grating onto an etched structure and a Bragg grating based sensor
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Deng, Zhijie. "Novel optical devices for information processing." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5863.
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Optics has the inherent advantages of parallelism and wide bandwidths in processing
information. However, the need to interface with electronics creates a bottleneck
that eliminates many of these advantages. The proposed research explores novel
optical devices and techniques to overcome some of these bottlenecks. To address
parallelism issues we take a specific example of a content-addressable memory that can
recognize images. Image recognition is an important task that in principle can be done
rapidly using the natural parallelism of optics. However in practice, when presented
with incomplete or erroneous information, image recognition often fails to give the
correct answer. To address this problem we examine a scheme based on free-space
interconnects implemented with diffractive optics. For bandwidth issues, we study
possible ways to eliminate the electronic conversion bottleneck by exploring all-optical
buffer memories and all-optical processing elements. For buffer memories we examine
the specific example of slow light delay lines. Although this is currently a popular
research topic, there are fundamental issues of the delay-time-bandwidth product
that must be solved before slow light delay lines can find practical applications. For
all-optical processing we examine the feasibility of constructing circuit elements that
operate directly at optical frequencies to perform simple processing tasks. Here we
concentrate on the simplest element, a sub-wavelength optical wire, along with a
grating coupler to interface with conventional optical elements such as lenses and
fibers. Even such a simple element as a wire has numerous potential applications. In conclusion, information processing by all-optical devices are demonstrated with
an associative memory using diffractive optics, an all-optical delay line using room
temperature slow light in photorefractive crystals, and a subwavelength optical circuit
by surface plasmon effects.
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Kieu, Khanh Quoc. "Novel Devices for Fiber Laser Application." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/193657.
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In this thesis, several novel devices for fiber laser are proposed and demonstrated. The first type of device is based on modal interference in non-adiabatic fiber tapers. Using such tapers, we demonstrate a simple technique to tune the wavelength of an all-fiber erbium-doped laser. Next, we systematically investigate the use of non-adiabatic fiber tapers for sensing purposes. As a result of this investigation, we have built and characterized several simple and sensitive sensors for highly accurate measurements of strain, temperature, and refractive index.Another class of devices investigated in this dissertation is based on micro-cavities. We propose and demonstrate, for the first time, the use of high-Q micro-spherical resonators as feedback mirrors for fiber lasers. The advantages of these new "mirrors" include compactness, low cost, tunability of the reflection coefficient, and an extremely narrow reflection bandwidth.We demonstrate single-frequency and Q-switched fiber lasers based on micro-spherical mirrors. The next natural step in the development of fiber-lasers involves the phenomenon of mode-locking. For this purpose, we developed a novel type of saturable absorber based on a fiber-taper embedded in a carbon nanotube/polymer composite material (FTECntPC). Subsequently, mode-locking was successfully demonstrated in an erbium-doped fiber laser using the aforementioned FTECntPC saturable absorber. We have thoroughly investigated the dynamics of passively mode-locked fiber lasers that incorporate the FTECntPC saturable absorber. With this new saturable absorber we have been able to obtain the highest pulse energies that have been generated to date directly from a soliton all-fiber laser. In addition, with the help of the novel saturable absorber, we have been able to build and analyze the first bi-directional passively mode-locked fiber laser.
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de, Souza Savita. "Digital watermarking and novel security devices." Thesis, De Montfort University, 2003. http://hdl.handle.net/2086/5847.
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This research is in the field of document security and the investigation of existing security devices. Security documents can be of two types; those that have commercial value, namely currency, articles of value and those that have legal value, namely, passports, identification cards etc. It is of vital importance in today's world, where fraud and counterfeiting are the order of the day, to protect any article or document of aesthetic importance and value. After the tragic events of September 11th 2001, security and the lack of security in every sense of the word is a much talked and researched subject. The literature review in Chapter Two will reveal that there are many security devices being currently used for various applications and each of them has many advantages and disadvantages. Devices such as magnetic cards, chip cards, biometric technology, optically variable devices, holograms and kinegrams and others have been described and their uses explained. Chapter Three is a continuation of literature review on Digital Watermarking and the available Digimarc technologies and applications in the field of security. Digimarc Corporation, based in Tualatin, Oregon, United States has been the pioneer in the field of Digital Watermarking. Microbar Security Limited, a subsidiary company of Durand Technology Limited, based at the Shrivenam 100 Business Park, Shrivenam, Oxfordshire, United Kingdom has developed its own watermarking technique, which has many advantages in comparison to the Digimarc Technology has also been described here.In Chapter Four, an optical variable device, namely, the Lippmann Optical Variable Device, named after the nineteenth century scientist Gabriel Lippmann (1845-1921), has been studied in thorough detail. Much work has been done to prove it and to understand the principle behind the theory he proposed. Currently, this type of technique based on interferential photography can be applied as a unique security device on passports, identification cards etc. The principles and theory of Lippmann photography has been explained in considerable detail. Experimental work done using various methods and using different photographic materials has also been described along with the results obtained. The application that has been emphasized here, is for passports for which this research was conducted in collaboration with Holographic Dimensions, Florida. Chapter Five, explains the principle of Covert Bar Coding which is the basis of the Microbar Watermarking Technique. Experimental results have been presented, these have been obtained using the MATLAB software. Finally, Chapter Six gives some ideas that can be pursued for future work. This work has produced two papers on Lippmann Photography and the mathematical evaluation of the emulsion co-authored by the author of the thesis. Abstracts from the papers have been used in this thesis. Also, it has produced two patents, one by `Holographic Dimensions', Florida on the Lippmann Photography and second, `Microbar Security Limited' on the `Covert Bar Coding Technique'.
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Russell, Ben. "Modelling of novel opto-electronic devices." Thesis, University of York, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444759.
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Hsieh, Pei-Shan. "IGBT design, modelling and novel devices." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708993.
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Choi, DongWoong. "Novel materials for energy storage devices." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10045888/.
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Andreakou, Peristera. "Hybrid nanomaterials for novel photonic devices." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/347152/.
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This PhD thesis investigates the optical properties of colloidal semiconductor nanocrystals and evaluates concepts regarding the development of novel photonic devices. Spectroscopic studies of the exciton dynamics in colloidal lead sulfide (PbS) quantum dots (QDs) by tuning the temperature are presented. The lowest exciton splitting for a range of PbS QDs sizes is calculated and a transfer of the oscillator strength from dark to bright states as the size increases is demonstrated. Hybrid structures with PbS QDs deposited on silicon substrates were also studied in order to explore whether excitons can be created in this material by means of resonant energy transfer. Furthermore, elongated asymmetric cadmium selenide/cadmium sulfide (CdSe/CdS) quantum rods are used as gain medium for the development of whispering gallery mode microlasers. Single-mode operation of hybrid lasers based on colloidal CdSe/CdS core/shell QRs in silica microspheres is for the first time reported. Laser-emission tunability over a range of 2.1 nm is also demonstrated, by heating the microsphere cavity with a 3.5-μm laser. In the last part of this thesis, unstructured and micro structured LiNbO3 are presented as excellent substrates for cell culture. Two commonly used neuron-like cells have been successfully proliferated and differentiated on both polar (±z) faces of LiNbO3 crystal substrates. Spatially selective attachment of neuron-like cells onto the domain engineered micro-structured substrates is also shown, providing the opportunity for the development of functional materials for the study of neuronal networks.
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Smith, Helen. "Novel organic materials for photovoltaic devices." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5859/.
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Organic materials offer key advantages over their inorganic counterparts for photovoltaics due to the ability to easily tune the physical properties and develop cheaper, more flexible, photovoltaic devices. This thesis describes the synthesis and characterisation of a variety of compounds from small-molecule to supramolecular and polymeric systems with the potential to be used in organic electronics. Herein is described an optimised synthetic route for the synthesis of two flavins and the synthesis and characterisation of a novel flavin and fluorene polymer. Also described is the synthesis of two novel rotaxane structures with the potential for use in organic field effect transistors. The synthesis of a novel polymer incorporating the naphthalene diimide moiety and a P3HT functionality utilising click methodology is also described. Finally the synthesis of a thiophene based star shaped molecule as electron transporting material is also described along with a flavin based organic dye for use in dye-sensitised solar cells.
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Chen, Feng. "Ferroelectric electron emission induced by high voltage polarization switching." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275328.
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Stevenson, Paul. "Novel plasma sources for the plasma opening switch." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/13632.
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The plasma opening switch (POS) is used in pulsed power systems where a fast opening and very high current switch is required. Plasma is injected into the switch, which carries a large conduction current before it opens in a process that lasts for a few nanoseconds and transfers the current to a parallel-connected load The conduction and opening times of the switch are dependent on the plasma parameters such as distribution, speed, temperature and species, which are all determined by the plasma source. This thesis begins with a description of the POS, with its conduction and opening mechanisms and the techniques of plasma generation all being considered, before it concentrates on the simple and inexpensive carbon gun. Plasma is normally produced by a pulsed discharge that evolves plasma from the evaporation and ionisation of a carbon based insulator. The first prototype carbon gun discussed in the thesis uses a classical coaxial arrangement that successfully produces dense, fast and hot plasma, although this is only capable of filling a small region with plasma. A number of plasma diagnostic techniques are described, before details are provided of the electrical probes that were used to characterise the plasma In a large POS a well-distributed plasma is obtained by combining a large number of guns in a complex and large system. This restncts the compactness of the POS resulting in a problem for any future commercial applications. A succession of developments to the prototype gun has led to a novel ring-shaped version that produces a much improved distribution of plasma, without the need for additional guns. In this, a pulsed discharge is initiated at a single point and the self-generated magnetic field forces the discharge to spread and to travel around the gun, whilst continuously ejecting plasma into the POS. The ideas and theories that explain how a discharge can be forced to move are described, together with details of the prototype designs. Results are given to confirm the operation of the gun, using high speed photography and electrical probes.
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Holcroft, B. "Novel electronic devices incorporating Langmuir-Blodgett films." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235171.
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Bhuwalka, Krishna K. "Novel tunneling devices for future CMOS technologies." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980688434.
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Persson, Stefan. "Modeling and characterization of novel MOS devices." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3720.
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Challenges with integrating high-κ gate dielectric,retrograde Si1-xGexchannel and silicided contacts in future CMOStechnologies are investigated experimentally and theoreticallyin this thesis. ρMOSFETs with either Si or strained Si1-xGex surface-channel and different high-κgate dielectric are examined. Si1-xGex ρMOSFETs with an Al2O3/HfAlOx/Al2O3nano-laminate gate dielectric prepared by means ofAtomic Layer Deposition (ALD) exhibit a great-than-30% increasein current drive and peak transconductance compared toreference Si ρMOSFETs with the same gate dielectric. Apoor high-κ/Si interface leading to carrier mobilitydegradation has often been reported in the literature, but thisdoes not seem to be the case for our Si ρMOSFETs whoseeffective mobility coincides with the universal hole mobilitycurve for Si. For the Si1-xGexρMOSFETs, however, a high density ofinterface states giving riseto reduced carrier mobility isobserved. A method to extract the correct mobility in thepresence of high-density traps is presented. Coulomb scatteringfrom the charged traps or trapped charges at the interface isfound to play a dominant role in the observed mobilitydegradation in the Si1-xGexρMOSFETs.
Studying contacts with metal silicides constitutes a majorpart of this thesis. With the conventional device fabrication,the Si1-xGexincorporated for channel applications inevitablyextends to the source-drain areas. Measurement and modelingshow that the presence of Ge in the source/drain areaspositively affects the contact resistivity in such a way thatit is decreased by an order of magnitude for the contact of TiWto p-type Si1-xGex/Si when the Ge content is increased from 0 to 30at. %. Modeling and extraction of contact resistivity are firstcarried out for the traditional TiSi2-Si contact but with an emphasis on the influenceof a Nb interlayer for the silicide formation. Atwo-dimensional numerical model is employed to account foreffects due to current crowding. For more advanced contacts toultra-shallow junctions, Ni-based metallization scheme is used.NiSi1-xGex is found to form on selectively grown p-typeSi1-xGexused as low-resistivity source/drain. Since theformed NiSi1-xGex with a specific resistivity of 20 mWcmreplaces a significant fraction of the shallow junction, athree-dimensional numerical model is employed in order to takethe complex interface geometry and morphology into account. Thelowest contact resistivity obtained for our NiSi1-xGex/p-type Si1-xGexcontacts is 5´10-8Ωcm2, which satisfies the requirement for the 45-nmtechnology node in 2010.
When the Si1-xGexchannel is incorporated in a MOSFET, it usuallyforms a retrograde channel with an undoped surface region on amoderately doped substrate. Charge sheet models are used tostudy the effects of a Si retrograde channel on surfacepotential, drain current, intrinsic charges and intrinsiccapacitances. Closed-form solutions are found for an abruptretrograde channel and results implicative for circuitdesigners are obtained. The model can be extended to include aSi1-xGexretrograde channel. Although the analytical modeldeveloped in this thesis is one-dimensional for long-channeltransistors with the retrograde channel profile varying alongthe depth of the transistor, it should also be applicable forshort-channel transistors provided that the short channeleffects are perfectly controlled.
Key Words:MOSFET, SiGe, high-k dielectric, metal gate,mobility, charge sheet model, retrograde channel structure,intrinsic charge, intrinsic capacitance, contactresistivity.
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Murray, James Thomas. "Novel devices and techniques in nonlinear optics." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/187519.
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A novel nonlinear frequency conversion technique based on intracavity stimulated Raman scattering in solid-state media is discussed. Devices have been built which are based on this technique. Standard first-order resonator eigenmode routines as well as paraxial diffraction-propagation, laser gain and nonlinear conversion routines have been integrated into a generalized laser resonator design software package which can accurately model the growth and evolution of the transverse field distribution in arbitrary intra- or extra-cavity nonlinear frequency converted laser sources. This package has been implemented as a design tool and has been utilized to model intracavity Raman beam cleanup. The macroscopic and microscopic pulse dynamics are modeled by rate equation and roundtrip pulse intensity iterator routines, respectively. A host of dynamical features are predicted theoretically and confirmed by experiment; such as, nonlinear cavity dumping, gain switching, dynamical chaos, and self-mode-locking. A new theory based on probabilistic arguments is developed to describe the spectral properties of intracavity Raman lasers. It is shown that under normal conditions, the Raman gain profile which results from multimode pumping is inhomogeneously broadened. Questions of efficiency, cavity matching, injection seeding and locking are addressed. Phase-matching and conversion efficiency in optically active second-order nonlinear materials is treated theoretically. Also examined are the conditions under which optical activity significantly alters the nonlinear optical properties of a material and show how this mechanism might be used in designing a nonlinear optical device. Corrections to the standard theoretical expressions for birefringent phase-matching angles and conversion efficiency are obtained for application to biaxial crystals with large natural birefringence. A generalized quasi-phase-matching scheme based on optical activity is formulated for three-wave interactions in second-order nonlinear crystals. A technique based on optical parametric generation and amplification is utilized to accurately determine the dispersion of the nonlinear susceptibilities in thin-film samples. Intrinsic pump-energy instabilities are taken into account in the data analysis.
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Richards, Gary J. "Novel organic materials for electroluminescent display devices." Thesis, University of Hull, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342862.
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Jennings, Michael Robert. "Novel Contact Formation for 4H-SiCPower Devices." Thesis, University of Warwick, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504862.
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SiC is seen as the material of choice for the next generation of power semiconductor devices because of its potential to deliver high power densities whilst maintaining high efficiency levels. The novel contact formation examined in this· thesis is aimed at improving the robustness and ohmicity of contacts to 4H-SiC. Innovative triple and multiple metallisations based on a combination of Al/Ti and Al/Ni layers have been fabricated, which are aimed at reducing the contact resistance and improving the contact morphology to p-type 4H-SiC. The lowest specific contact resistivity obtained was based on a triple layer AI/Ti/Al contact, measured at 5.0 x 10-6 Ocm2 This value approaches the state of the art. The multiple layered contacts all dis- . played Schottky-like characteristics even after high temperature annealing. X-ray diffraction scans have indicated enhanced formation of metal silicides with respect to the ohmic triple layered contacts based on Al/Ti (Ti3SiC2) and Al/Ni (NiSix ). Low levels of silicide formation have been found in multiple layered contacts. Scanning electron microscope examination and wavelength dispersive analysis point to the fact that multiple layered contacts display a superior morphology, reducing the amount of Al spreading, which is known to be problematic during a high temperature anneal. A physical and electrical investigation of silicon contact layers grown by molecular beam epitaxy on n-type 4H-SiC (Si/SiC) has been conducted. The effect of the silicon doping concentration, growth temperature and SiC surface cleaning prior to growth have been evaluated. X-ray diffraction and scanning electron microscope analysis have been utilised for the purpose of evaluating the morphology and crystal structure of grown silicon layers. I-V and e-V measurements have shown the rectifying properties of the Si/SiC heterojunction along with their corresponding built-in potentials and energy band offsets. Modelling of Si/SiC heterojunction diodes revealed that the current characteristics can be explained by an isojunction drift-diffusion and thermionic emission model. The modelling results point to the fact that I-V properties of Si/SiC n-N heterojunction diodes are relatively independent of the doping concentration of the grown silicon layer. Preliminary . results obtained from p-type silicon grown by molecular beam epitaxy on n-type 4H-SiC have been presented. A possible application for Si/SiC layers is a vertical heterojunction MOSFET. The establishment of 4H-SiC PiN diode technology is discussed. Scanning electron microscope examination has been utilised for the purpose of evaluating PiN diode fabrication based on shadow masking and liftoff techniques. Reverse bias I-V measurements highlight the fact that mesa isolated PiN diodes display around 5 orders of magnitude lower leakage currents with respect to their un-isolated counterparts. Forward bias I-V measurements have compared performances of diodes with different anode metallisations based on AI, Ni and Ti layers. PiN diodes based on Ti show lower turn-on voltages while mesa isolated PiN diodes displayed higher current densities and more ideal forward characteristics when compared to their un-isolated counterparts. __.
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Jollivet, Clemence. "Specialty Fiber Lasers and Novel Fiber Devices." Doctoral diss., University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6295.
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At the Dawn of the 21st century, the field of specialty optical fibers experienced a scientific revolution with the introduction of the stack-and-draw technique, a multi-steps and advanced fiber fabrication method, which enabled the creation of well-controlled micro-structured designs. Since then, an extremely wide variety of finely tuned fiber structures have been demonstrated including novel materials and novel designs.
As the complexity of the fiber design increased, highly-controlled fabrication processes became critical. To determine the ability of a novel fiber design to deliver light with properties tailored according to a specific application, several mode analysis techniques were reported, addressing the recurring needs for in-depth fiber characterization.
The first part of this dissertation details a novel experiment that was demonstrated to achieve modal decomposition with extended capabilities, reaching beyond the limits set by the existing mode analysis techniques. As a result, individual transverse modes carrying between ~0.01% and ~30% of the total light were resolved with unmatched accuracy. Furthermore, this approach was employed to decompose the light guided in Large-Mode Area (LMA) fiber, Photonic Crystal Fiber (PCF) and Leakage Channel Fiber (LCF). The single-mode performances were evaluated and compared. As a result, the suitability of each specialty fiber design to be implemented for power-scaling applications of fiber laser systems was experimentally determined.
The second part of this dissertation is dedicated to novel specialty fiber laser systems. First, challenges related to the monolithic integration of novel and complex specialty fiber designs in all-fiber systems were addressed. The poor design and size compatibility between specialty fibers and conventional fiber-based components limits their monolithic integration due to high coupling loss and unstable performances. Here, novel all-fiber Mode-Field Adapter (MFA) devices made of selected segments of Graded Index Multimode Fiber (GIMF) were implemented to mitigate the coupling losses between a LMA PCF and a conventional Single-Mode Fiber (SMF), presenting an initial 18-fold mode-field area mismatch. It was experimentally demonstrated that the overall transmission in the mode-matched fiber chain was increased by more than 11 dB (the MFA was a 250 ?m piece of 50 ?m core diameter GIMF). This approach was further employed to assemble monolithic fiber laser cavities combining an active LMA PCF and fiber Bragg gratings (FBG) in conventional SMF. It was demonstrated that intra-cavity mode-matching results in an efficient (60%) and narrow-linewidth (200 pm) laser emission at the FBG wavelength.
In the last section of this dissertation, monolithic Multi-Core Fiber (MCF) laser cavities were reported for the first time. Compared to existing MCF lasers, renown for high-brightness beam delivery after selection of the in-phase supermode, the present new generation of 7-coupled-cores Yb-doped fiber laser uses the gain from several supermodes simultaneously. In order to uncover mode competition mechanisms during amplification and the complex dynamics of multi-supermode lasing, novel diagnostic approaches were demonstrated. After characterizing the laser behavior, the first observations of self-mode-locking in linear MCF laser cavities were discovered.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics and Photonics
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Young, Sue Y. "Characterization of novel III-V semiconductor devices." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37094.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 68-69).
This thesis presents the characterization of tunnel junctions and tunnel-junction-coupled lasers. The reverse-biased leakage current in a tunnel junction can be exploited to tunnel electrons from the valence band of one active region to the conduction band of a second active region. Thus, tunnel-junction-coupled lasers are highly efficient as they allow electrons to stimulate the emission of photons in more than one active region. The electrical characterization of InGaAs/GaAs tunnel junctions is presented. This thesis also gives an overview of the electrical and optical behavior of single-stage lasers as well as two-stage lasers coupled by InGaAs/GaAs tunnel junctions. Telecommunication applications motivated the use of InAs quantum dots and InAsP quantum dashes in the active layer design to provide near-infrared emission.
by Sue Y. Young.
M.Eng.
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Pathirana, Gamarachchi Pathiranage Vasantha. "Novel lateral power devices on insulating substrates." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613830.
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Chai, Zheng. "Characterisation of novel resistive switching memory devices." Thesis, Liverpool John Moores University, 2017. http://researchonline.ljmu.ac.uk/6937/.
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Resistive random access memory (RRAM) is widely considered as a disruptive technology that will revolutionize not only non-volatile data storage, but also potentially digital logic and neuromorphic computing. The resistive switching mechanism is generally conceived as the rupture/restoration of defect-formed conductive filament (CF) or defect profile modulation, for filamentary and non-filamentary devices respectively. However, details of the underlying microscopic behaviour of the resistive switching in RRAM are still largely missing. In this thesis, a defect probing technique based on the random telegraph noise (RTN) is developed for both filamentary and non-filamentary devices, which can reveal the resistive switching mechanism at defect level and can also be used to analyse the device performance issues. HfO2 is one of the most matured metal-oxide materials in semiconductor industry and HfO2 RRAM shows promising potential in practical application. An RTN-based defect extraction technique is developed for the HfO2 devices to detect individual defect movement and provide statistical information of CF modification during normal operations. A critical filament region (CFR) is observed and further verified by defect movement tracking. Both defect movements and CFR modification are correlated with operation conditions, endurance failure and recovery. Non-filamentary devices have areal switching characteristics, and are promising in overcoming the drawbacks of filamentary devices that mainly come from the stochastic nature of the CF. a-VMCO is an outstanding non-filamentary device with a set of unique characteristics, but its resistive switching mechanism has not been clearly understood yet. By utilizing the RTN-based defect profiling technique, defect profile modulation in the switching layer is identified and correlated with digital and analogue switching behaviours, for the first time. State instability is analysed and a stable resistance window of 10 for >106 cycles is restored through combining optimizations of device structure and operation conditions, paving the way for its practical application. TaOx-based RRAM has shown fast switching in the sub-nanosecond regime, good CMOS compatibility and record endurance of more than 1012 cycles. Several inconsistent models have been proposed for the Ta2O5/TaOx bilayered structure, and it is difficult to quantify and optimize the performance, largely due to the lack of microscopic description of resistive switching based on experimental results. An indepth analysis of the TiN/Ta2O5/TaOx/TiN structured RRAM is carried out with the RTN-based defect probing technique, for both bipolar and unipolar switching modes. Significant differences in defect profile have been observed and explanations have been provided.
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Abernethy, Joyce Anne. "Novel devices in periodically poled lithium niobate." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/15473/.
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This thesis describes the research carried out to develop several novel periodically poled lithium niobate (PPLN) devices. These devices exploit the ability to invert micro-domains of spontaneous polarisation in ferroelectrics such as lithium niobate. The fabrication of PPLN devices is described and extensive studies into factors influencing the poling quality are presented. In particular a comparison of material properties of unprocessed lithium niobate material from a range of different suppliers is carried out. Several novel PPLN devices are reviewed and two main devices are investigated - an electro-optically controlled Bragg grating modulator for laser beam switching and modulation and a titanium indiffused waveguide in PPLN for frequency conversion. The design, fabrication and operation of the electro-optic Bragg modulators is described and results for the first infrared operation at 1064nm of such a device are presented. Several discrepancies are seen between experimental results, both in this thesis and previously published results, and a theoretical model based on Kogelnick?s coupled wave analysis. These anomalies are further investigated at visible operation (633nm and 488nm) and solutions and methods for alleviating the discrepancies are presented. Work on titanium indiffused channel waveguides in PPLN is reported, including a study into fabrication issues and the demonstration of second harmonic generation of 416nm in such a device.
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Middendorf, John Raymond. "Novel Devices and Components for THz Systems." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1400252710.
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Al-Amer, Itihad Abd Al-Hameed Abd. "A stable doubly-fed machine with novel rotor design." Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335349.
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Thong, Yee Keat. "A novel computer interface tool using low cost inertial sensors." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246360.
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Wong, J. N. H. "Novel techniques for improving the performance of MESFET power amplifiers." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/843448/.
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This thesis describes the research activities that have been investigated for improving the 3rd order intermodulation distortion products (IM3) and power added efficiency (PAE) and bandwidth performance of microwave GaAs MESFET power amplifiers. Two novel circuit techniques, one for improving the 3dB bandwidth performance and the other for improving the IM3 and PAE performance, were proposed and verified through simulation and practical measurements. The technique of including lumped elements matching networks within the package encapsulation (Close-to-Chip lumped element matching) of a 2GHz MESFET device is described for the first time. Simulation results showed that the amplifier using this technique had a 3dB bandwidth 3 times wider than the amplifier with Off-Chip distributed element matching. The linearity and efficiency performance of a 2GHz MESFET was improved significantly by presenting a difference frequency shunt short-circuit termination across the drain terminal. A 16dB reduction in IM3 and an improvement of 4% in PAE performance was measured on the bench. Success with this technique was further demonstrated with digitally modulated signals.
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Udrea, Florin. "Novel MOS-gated bipolar device concepts towards a new generation of power semiconductor devices." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/265438.
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Research in MOS-gated power semiconductor devices with combined bipolarlVIOS action has been motivated by the continuous industrial need for highly efficient devices with reduced power losses and high impedance gate control. The Insulated Gate Bipolar Transistor (IGBT) and the IVIOS Controlled Thyristor (MCT) have been among the first :tvIOS-gated bipolar devices with high blocking capability and reduced on-state power losses. Presently these devices are fabricated using the conventional DIVIOS technology. Recently, a new technology, trench technology, has emerged in the field of low voltage power :tvIOSFETs. This thesis discusses the fundamental physical and geometrical advantages of the trench technology over the conventional technologies for high voltage devices. New physical phenomena such as channel length modulation, enhanced channel charge and the PIN diode effect are reported for the first time. A physically-based on-state analytical model for Trench Insulated Gate Bipolar Transistors (Trench IGBTs) is developed. Furthermore, the present study proposes a novel bipolar-MOS concept, termed Inversion Layer Injection. Unlike in conventional bipolar-MOS devices where the bipolar emitter is formed by a "static" semiconductor layer (e.g. n+ type), in this case the bipolar emitter is constituted by mobile carriers ( e.g. electrons), which can be directly controlled by an external gate electric field. Based on this physical principle, a trench-gated device termed the Inversion Layer Emitter Thyristor is proposed. The ILET has the potential to achieve an optimum on-state/turn-off performance and is suitable for a very wide range of applications which require voltage ratings from 400 V up to 5 KV and operating current densities from 100 A/cm2 to 500 A/cm2 . The Inversion Layer Injection concept is further employed in a novel class of power semiconductor devices called Lateral In version Layer Emitter Transistors (LILETs ). The LILETs exhibit low on-state losses, very fast switching time, improved gate control and flexible mode operation. It is concluded that the Trench IGBT and ILET will play the major role in the next generation of high voltage vertical power devices. At the same time, the LILETs are regarded as potential CMOS compatible structures for power int egrated circui ts which can replace the conventional Lateral In sulated Gate Bipolar Transistors (LIGBTs).
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Tian, Zhaobing. "Novel optical fiber devices for emerging optical applications." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114472.
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With dramatically increasing internet bandwidth, electrons as information carriers are being continually replaced with photons. This exchange has been fully completed in the long-haul high-speed backbone network, now occurs in short-reach data centers and radio frequency communications, and eventually will reach the chip level. Various emerging optical technologies have been developed during this time; with performance and cost being the two major factors to be considered for these technologies. In this work, we propose and design several novel optical fiber devices to enhance the performance or lower the associated cost of emerging technologies in the areas of microcavities and dual-mode fibers. Self-rolled-up semiconductor microtubes have been very promising in integrated optical circuits due to their unique fabrication method and their smooth surfaces. In spite of extensive study on various materials and applications, the properties of these microtubes at telecom wavelengths have not been explored. We propose and demonstrate a fiber-based solution to obtain precise single device transfer, the highest Q-factor (1.5×105) measurement, selective polarization excitation, optical-optical modulation, and the thermal dynamic effect of these microtubes. The microtubes exhibit ideal optical performance at telecom wavelengths and are a good microcavity candidate for integration with silicon photonics.Compared to semiconductor microcavities, optical fiber microcavities have the advantages of a single device fabrication process, ultra smooth surface, and easy characterization with fiber optics. The microcavities have been reported in the shapes of spheres, bottles, and bubbles. Here we propose and demonstrate a novel optical fiber microdisk with a small free spectral range and a small mode cross section. The Q-factor of the microdisk is 7.8×106 and it is demonstrated as a narrow reflection mirror in a fiber ring laser. This microdisk would be of great interest for optical nonlinear applications. We propose three optical fiber devices for dual-mode fiber emerging technologies. First, we design an in-line Mach-Zehnder interferometer by offset splicing a length of dual-mode fiber with two regular single-mode fibers. This interferometer has been successfully applied for picoseconds flat-top pulse generation. Secondly, we propose and demonstrate a mode multiplexer consisting of a LP11 mode spatial rotator and a LP01/LP11 mode coupler. This mode multiplexer can be used in both short-reach data centers and long-haul mode division multiplexing. Thirdly, we propose a fiber coupler enabling conversion of a phase modulation to a mode modulation, which could lead to low cost ultra-wide band signal generation, novel advanced modulation formats, and optical switching.Avec les bandes passantes Internet qui augmentent considérablement, les électrons sont continuellement remplacées par des photons comme porteurs d'information. Cet échange, qui a été entièrement effectué dans le réseau fédérateur long-courrier à grande vitesse, se produit maintenant dans les centres de données de courte portée ainsi que pour les communications par fréquences radio et finiront par atteindre le niveau de la puce. Diverses nouvelles technologies optiques ont été développées durant cette période et la performance et le coût sont les deux principaux facteurs à prendre en considération pour ces technologies. Dans cette thèse, nous proposons et concevons plusieurs nouveaux dispositifs à fibres optiques pour améliorer la performance et réduire le coût des technologies émergentes dans les domaines des micro-cavités et des fibres bimodales.Les microtubes semi-conducteurs enroulés sur eux-même ont été très prometteurs dans les circuits optiques intégrés en raison de leur procédé de fabrication unique et de leurs surfaces lisses. En dépit d'une étude approfondie sur les différents matériaux et applications, les propriétés de ces microtubes n'ont pas été explorées pour les longueurs d'onde des télécommunications. Nous proposons et démontrons une solution avec fibres optiques pour obtenir le transfert précis d'un seul dispositif, la plus haut mesure de facteur Q (1.5 × 105), l'excitation d'une polarisation sélective, la modulation optique et l'effet thermique dynamique de ces microtubes. Les microtubes présentent des performances optiques idéales aux longueurs d'onde des télécommunications et sont de bons candidats pour l'intégration avec la photonique sur silicium.Par rapport aux microcavités semi-conductrices, les microcavités à fibres optiques ont l'avantage de posséder un procédé de fabrication pour un seul dispositif, d'avoir une surface ultra-lisse et d'être faciles à caractériser avec une fibre optique. Les microcavités ont été signalées sous les formes de sphères, de bouteilles et de bulles. Ici, nous proposons et démontrons une nouvelle fibre optique en forme de microdisque avec un petit intervalle spectral libre et un profil d'intensité étroit. Le facteur Q du microdisque est 7.8 × 106 et il est indiqué comme un miroir de réflexion étroit dans un laser à fibre en anneau. Ce microdisque serait d'un grand intérêt pour les applications optiques non linéaires.Nous proposons trois dispositifs à fibres optiques pour les technologies de fibres bimodales émergentes. Tout d'abord, nous concevons un filtre Mach-Zehnder par l'épissage d'une longueur de fibre bimodale entre deux fibres monomodes régulières. Cet interféromètre a été utilisé avec succès pour la génération d'impulsions picosecondes à sommet plat. Deuxièmement, nous proposons et démontrons un multiplexeur composé d'un rotateur spatial de mode LP11 et d'un coupleur de mode LP01/LP11. Ce multiplexeur de modes peut être utilisé à la fois dans les centres de données de courte portée et le multiplexage par réseau fédérateur long-courrier. Troisièmement, nous proposons un coupleur de fibres permettant une conversion de la modulation de phase à une modulation de mode, ce qui pourrait conduire à la génération de signaux à bandes ultra-large et à faibles coûts, à de nouveaux formats de modulation avancés ainsi qu'à la commutation optique.
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Texidó, Bartes Robert. "Novel electronic stretchable materials for future medical devices." Doctoral thesis, Universitat Ramon Llull, 2017. http://hdl.handle.net/10803/402945.
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L’electrònica convencional basada en el silici te grans dificultats a l’hora de ser implementada en dispositius electrònics que estiguin en contacte amb les corbes i las plasticitat dels teixits del cos humà. Futures aplicacions mèdiques como la pell electrònica, sistemes de alliberació de fàrmac transdèrmic o nous bio-sensors requereixen de sistemes electrònics capaços de ser doblegats, retorçats o enrotllats en superfícies corbes. Tot i els prometedors resultats mostrats por la investigació en electrònica flexible, no hi ha aplicacions comercials directes dins de l’àrea mèdica. La dependència de components només presents en l’electrònica convencional limita el complet desenvolupament d’aquests dispositius posant de manifest la necessitat de trobar nous materials en aquest camp.
Amb l’objectiu de potenciar nous sistemes electrònics flexibles, en aquest treball es proposen noves estratègies per proveir de flexibilitat als materials utilitzats en electrònica sense perdre de vista la directa aplicabilitat. Primerament, s’ha estudiat l’aplicació de polímers conductors mitjançant impressió inkjet. Aquesta tecnologia permet l’obtenció de films polimèrics molt fins sobre sistemes flexibles més complexos. Anant un pas més enllà, s’han desenvolupat noves metodologies per poder depositar polímers conductors sobre substrats elastomèrics mantenint el bon rendiment elèctric. Aquesta part culmina amb l’estudi d’un nou polielectròlit per la síntesis del polipirrol basat en l’àcid hialurònic modificat amb grups dopamina. Aquest polielectròlit aporta noves propietats que milloren l’adaptabilitat del polipirrol obtenint nanosuspensions estables que poden ser depositades directament sobre substrats elastomèrics.
Centrant-nos en los materials metàl·lics de la electrònica, s’ha desenvolupat un mètode per la deposició selectiva de plata conductora sobre substrats elastomèrics. Les pistes fabricades amb aquest procediment han demostrat un comportament de galga extensomètrica sota deformació mecànica.
Finalment la aplicabilitat de las estratègies desenvolupades ha estat avaluada per veure como es poden aplicar en dispositius mèdics actuals y futurs tals como sensors fisiològics, galgas extensomètriques portables para seguiment o nous stents de tràquea electrònics.La implementación de la electrónica convencional basada en el silicio en dispositivos electrónicos que entren en contacto con la plasticidad y las curvas de los tejidos del cuerpo humano presenta serias dificultades. Futuras aplicaciones médicas como la piel electrónica, sistemas de liberación de fármaco transdérmico o nuevos bio-sensores requieren sistemas electrónicos capaces de ser doblados, retorcidos o enrollados en superficies curvas. A pesar de los prometedores resultados mostrados por la investigación en electrónica flexible, muy pocas tecnologías se han visto adaptadas en una aplicación comercial dentro del área médica. Problemas como la dependencia de componentes solo presentes en la electrónica convencional limita el completo desarrollo de estos dispositivos poniendo de manifiesto la necesidad de encontrar nuevos materiales en este campo. Con el objetivo de potenciar nuevos sistemas electrónicos flexibles, este trabajo propone nuevas estrategias para aportar flexibilidad a los materiales empleado para la electrónica sin perder de vista su aplicabilidad. Primeramente, se ha estudiado la aplicación de polímeros conductores usando impresión inkjet. Esta tecnología permite la obtención de films poliméricos muy delgados sobre sistemas flexibles más complejos. Dando un paso más allá, se han desarrollado nuevas metodologías para poder depositar polímeros conductores sobre substratos elastómericos manteniendo un buen rendimiento eléctrico. Esta parte culmina con el estudio de un nuevo polielectrolito para la síntesis del polipirrol basado en el ácido hyaluronico modificado con dopamina. Este polielectrolito aporta nuevas propiedades que mejoran la adaptabilidad del polipirrol obteniendo nanosuspensiones estables que pueden ser depositadas directamente sobre substratos elastómeros. Estudiando también los materiales metálicos en la electrónica, se ha desarrollado un método para la deposición selectiva de plata conductora sobre substratos elastómeros. Las pistas fabricadas con este procedimiento han mostrado un interesante comportamiento de galga extensométrica cuando son sometidas a una deformación. Finalmente, la aplicabilidad de las estrategias desarrolladas ha sido evaluada para ver cómo se puede aplicar en dispositivos médicos actuales y futuros tales como sensores fisiológicos, galgas extenso métricas portables para seguimiento o nuevos stents traqueales electrónicos.
Conventional electronics based in rigid and planar silicon wafers presents several difficulties to be implemented in systems where a direct contact with the soft and curved geometries of the tissues of the human body is required. The future medical devices such as electronic skin, transdermal drug delivery systems or novel wearable biosensors requires electronic materials with the ability to be twisted, folded and conformably wrapped onto arbitrarily curved surfaces. Despite the promising results on stretchable electronic research, the applications have not yet been translated into commercial medical devices. The dependence of components still only present in conventional silicon electronics limits the full development of the stretchable strategies, revealing the need for new materials in this field. Aiming to potentiate new electronic stretchable systems, this works proposes novel strategies to provide stretchability to electronic materials always having in mind the final application. Firstly, the study of conducting polymers to be deposited using ink jet printing have been performed. This kind of implementation allows the formation of conductive thin films on more complex flexible systems. Going further, it has been developed novel methodologies using plasma treatments to fabricate conducting polymeric coating on stretchable substrate with good electrical performance. The culmination of this part consisted in the synthesis of polypyrrole with a novel polyelectrolyte based on a hyaluronic acid modified with dopamine groups that allows stable nanosuspension able to directly form a film onto stretchable substrates. Focusing on metallic materials, conductive silver deposition on selective stretchable substrate have been developed. The electrical performance under mechanical deformation revealed strange gauge sensor behaviour of the silver paths with promising applicability in the medical device. Finally, the applicability of the approaches developed in this work have been studied to evaluate its suitability on actual and future applications in the field of medical devices such as physiological sensors, wearable strain gauge sensors or tracheal stent able to monitor deformations.
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Yang, Rusen. "Oxide nanomaterials synthesis, structure, properties and novel devices /." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-06212007-161309/.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.Peter J. Hesketh, Committee Member ; Zhong Lin Wang, Committee Chair ; C.P. Wong, Committee Member ; Robert L. Snyder, Committee Member ; Christopher Summers, Committee Member.
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Ohbi, Daljit Singh. "Novel Elastomer Compositions for Medical Drug Delivery Devices." Thesis, University of Bolton, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494268.
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Dougall, Ewan A. "Investigation of oxygen transfer in novel medical devices." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16796.
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Kleemann, Hans. "Organic Electronic Devices - Fundamentals, Applications, and Novel Concepts." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-105059.
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This work addresses two substantial problems of organic electronic devices: the controllability and adjustability of performance, and the integration using scalable, high resolution patterning techniques for planar thin-film transistors and novel vertical transistor devices. Both problems are of particular importance for the success of transparent and flexible organic electronics in the future.
To begin with, the static behavior in molecular doped organic pin-diodes is investigated. This allows to deduce important diode parameters such as the depletion capacitance, the number of active dopant states, and the breakdown field. Applying this knowledge, organic pin-diodes are designed for ultra-high-frequency applications and a cut-off-frequency of up to 1GHz can be achieved using optimized parameters for device geometry, layer thickness, and dopant concentration.
The second part of this work is devoted to organic thin-film transistors, high resolution patterning techniques, as well as novel vertical transistor concepts. In particular, fluorine based photo-lithography, a high resolution patterning technique compatible to organic semiconductors, is introduced fielding the integration of organic thin-film transistors under ambient conditions. However, as it will be shown, horizontal organic thin-film transistors are substantially limited in their performance by charge carrier injection. Hence, down-scaling is inappropriate to enlarge the transconductance of such transistors. To overcome this drawback, a novel vertical thin-film transistor concept with a vertical channel length of ∼50nm is realized using fluorine based photo-lithography. These vertical devices can surpass the performance of planar transistors and hence are prospective candidates for future integration in complex electronic circuits.
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Penty, Richard Vincent. "Novel optical fibre Kerr devices for signal processing." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291606.
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Stienen, A. H. A. "Development of novel devices for upper-extremity rehabilitation." Enschede : University of Twente [Host], 2008. http://doc.utwente.nl/60511.
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Ring, Josh. "Novel fabrication and testing of light confinement devices." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/novel-fabrication-and-testing-of-light-confinement-devices(51572720-0c49-482e-8523-e44ca877117f).html.
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The goal of this project is to study novel nanoscale excitation volumes, sensitive enoughto study individual chromophores and go on to study new and exciting self assemblyapproaches to this problem. Small excitation volumes may be engineered using light con-finement inside apertures in metal films. These apertures enhance fluorescence emissionrates, quantum yields, decrease fluorescence quenching, enable higher signal-to-noiseratios and allow higher concentration single chromophore fluorescence, to be studied byrestricting this excitation volume. Excitation volumes are reported on using the chro-mophore's fluorescence by utilising fluorescence correlation spectroscopy, which monitorsfluctuations in fluorescence intensity. From the correlation in time, we can find the res-idence time, the number of chromophores, the volume in which they are diffusing andtherefore the fluorescence emission efficiency. Fluorescence properties are a probe ofthe local environment, a particularly powerful tool due to the high brightness (quantumyield) fluorescent dyes and sensitive photo-detection equipment both of which are readilyavailable, (such as avalanche photodiodes and photomultiplier tubes). Novel materialscombining the properties of conducting and non-conducting materials at scales muchsmaller than the incident wavelength are known as meta-materials. These allow combi-nations of properties not usually possible in natural materials at optical frequencies. Theproperties reported so far include; negative refraction, negative phase velocity, fluorescenceemission enhancement, lensing and therefore light confinement has also been proposed tobe possible. Instead of expensive and slow lithography methods many of these materialsmay be fabricated with self assembly techniques, which are truly nanoscopic and otherwiseinaccessible with even the most sophisticated equipment. It was found that nanoscaled volumes from ZMW and HMMs based on NW arrays wereall inefficient at enhancing fluorescence. The primary cause was the reduced fluorescencelifetime reducing the fluorescence efficiency, which runs contrary to some commentatorsin the literature. NW based lensing was found to possible in the blue region of the opticalspectrum in a HMM, without the background fluorescence normally associated with a PAAtemplate. This was achieved using a pseudo-ordered array of relatively large nanowireswith a period just smaller than lambda / 2 which minimised losses. Nanowires in the traditionalregime lambda / 10 produced significant scattering and lead to diffraction, such that they werewholly unsuitable for an optical lensing application.
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Bushell, Zoe L. "Development of novel infrared photonic materials and devices." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/841718/.
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This thesis investigates a range of novel photonic devices and their constituent semiconductor materials with emission in the infrared (IR) region of the spectrum. These have a variety of potential applications, including in telecoms, sensing and defence systems. Studies focus on aspects of the electronic and photonic band structures, and how these impact upon device performance. Type-II interband cascade lasers and LEDs emitting in the mid-IR region of 3 – 4 μm are characterised using temperature and hydrostatic pressure dependent techniques. The key finding is that the threshold current density exhibits a minimum for emission around 0.35 eV (~3.5 μm), in both the pressure dependent results and data for many devices with different design wavelengths. The increase in threshold current density towards lower energies can be explained by an increase in CHCC Auger recombination. The increase in threshold current towards higher energies cannot be well explained by an Auger process, and it is concluded that this may be evidence of defect-related recombination. Dilute bismide alloys are an interesting new material system for IR applications. The electronic and optical properties of several dilute bismide alloys are determined by spectroscopic ellipsometry. Key findings include the first experimental measurements of the spin-orbit splitting in GaNAsBi, which show that it is approximately independent of N content, and the first evidence for a decrease in the direct band gap of GaP with the addition of bismuth, reducing by 130 ± 20 meV/%Bi. The refractive index was determined for all the materials and in the transparency region the real part of the refractive index was found to decrease approximately linearly with increasing band gap. In addition to modifying the electronic properties, photonic effects can be used to develop new IR devices. Finite difference time domain simulations of photonic crystal cavity structures within thick multi-layer slabs were carried out. These showed that it is possible to achieve high Q-factors, > 10^4, in slabs with refractive indices corresponding to typical semiconductor heterostructures. This opens up possibilities for designing photonic crystal lasers that do not require the thin suspended membranes typically found in the literature, with applications in integrated photonic circuits and on-chip sensors.
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Klasner, Scott A. "Novel capillary and microfluidic devices for biological analyses." Diss., Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/3747.
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Cariello, Michele. "Synthesis of novel organic semiconductors for optoelectronic devices." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7805/.
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This thesis describes the synthesis and characterisation of novel conjugated organic materials with optoelectronic application. The first chapter provides an introduction about organic semiconductors and in particular about their working principle from a physical and chemical point of view. An overview of the most common types of solar cells is provided, including examples of some of the best performing materials. The second chapter describes the synthesis of a new library of flavin derivatives as potential active materials for optoelectronic applications. Flavins are natural redox-active molecules, which show potential application in optoelectronics, thanks to their stability and versatility. FPF-Flavins, for instance, could be used either as acceptor units in push-pull polyconjugated systems or as acceptor unit in dyes for DSSCs. In the same chapter a first attempt of synthesising bis-flavins to be used as N-type semiconductors in BHJ devices is described. The third chapter describes the successful synthesis and characterization of a series of conjugated organic molecules based on the benzothiadiazole moiety. Among these, three molecules containing ferrocene as donor unit were tested as sensitizers for DSSCs, reporting a PCE of 0.3% as the best result. Further studies indicated a significant problem of charge recombination which limits the performance. A near-infrared absorbing push-pull polymer, based on BbT as acceptor unit, was also synthesised and tested in BHJ devices as P-type semiconductor in blend with PC71BM, showing a VOC of 0.71 V. Finally, the last chapter describes the synthesis of several tetrathiafulvalene derivatives in order to explore this moiety as donor unit in dyes for DSSCs and as HTM for perovskite-based solar cells. In particular, two very simple dyes were synthesised and implemented in DSSCs reporting a PCE 0.2% and 0.4%, respectively. The low efficiency was associated to the tendency to aggregate at the solid state, with the absorption shifting from the visible to the infrared range. A conjugated molecule, containing a DPP core, was also synthesised and tested as HTM for perovskite solar cells. The best reported PCE of 7.7% was obtained without any additives. A case study about dehalogenation and “halogen dance” in TTF iodide is also presented.
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Dong, Liang. "Novel optical fibre devices based on MCVD method." Thesis, University of Southampton, 1992. https://eprints.soton.ac.uk/404723/.
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In this thesis, several new optical fibre devices are described. These devices are based on fibres with special structures or materials, fabricated by the MCVD technique. Light propagation and intermodal coupling in twin-core (TC) fibres are investigated both theoretically and experimentally. A cascaded TC fibre filter is demonstrated and so are TC fibre intermodal couplers using both mechanical gratings and fibre acoustic flexural waves, which can be used as filters, wavelength-division multiplexing (WDM) taps and frequency shifters. Photosensitivity in both transition-metal-doped fibre and cerium-doped fibre with applications for making fibre in-core gratings are also studied. UV-induced absorption and refractive index change are investigated. A large absorption change occurs when fibre is exposed to pulsed UV. The fibre IR loss eventually recovers to its original level. The UV-induced refractive index change in cerium fibre is found to be the same order of magnitude as that reported in germanosilicate fibres. Some other devices and effects, including a gold-implanted fibre polariser, excitation poling in second harmonic generation and a spatial model converter, are also studied. The gold-implanted polariser is much easier to be massproduced and spliced to an ordinary fibre with a low loss than its liquid-metal-implanted counterpart. Excitation poling gives an improved efficiency in second harmonic generation. The spatial model converter provides an easy low-loss connection for waveguides with different spatial modes.
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Gawith, Corin B. E. "Novel active waveguide devices in direct-bonded structures." Thesis, University of Southampton, 2002. https://eprints.soton.ac.uk/15488/.
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This thesis describes a series of experimental studies on the use of direct bonding for optical waveguide fabrication. The direct bonding technique involves contacting two ultra-clean polished surfaces to form an adhesive-free vacuum-tight bond. Optical materials bonded in this way can be formed into waveguide devices, and this work extends direct bonding to include periodically poled materials and a new solid-state ion-exchange process. The first result of this work describes the fabrication of a 5.5-mm-long, 12-µm-thick periodically poled LiNbO3 planar waveguide buried in LiTaO3. Frequency doubling experiments performed with this device demonstrate a conversion efficiency of 4.3 %W-1, a value 40% greater than that calculated for an optimised bulk device of similar length. Also demonstrated is a photorefractive iron-doped LiNbO3 waveguide buried in non-photorefractive magnesium-doped LiNbO3. In optical limiting experiments this device demonstrates a change in optical density of 2 and photorefractive response time of 5 milliseconds, representing 20 times greater optical limiting and 60 times faster operational speed than the bulk material. K+-Na+ ion-exchange between direct-bonded glass layers is studied and used as a novel solid-state technique for waveguide fabrication. This process is also developed to incorporate direct-UV-written channel waveguides in an ion-exchanged buried photosensitive glass layer. Finally, operation of a single-mode channel waveguide laser in neodymium-doped photosensitive SGBN glass (based on a composition of silica, germania, boron, and sodium) is demonstrated, with propagation losses of < 0.3 dB cm-1 and milliwatt-order lasing thresholds.
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Peacock, Anna Claire. "Applications of light propagation in novel photonic devices." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/42429/.
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In this thesis, the propagation of light in novel photonic devices has been studied theoretically, numerically and experimentally. In particular, self-similar solutions to the nonlinear Schrödinger equation have been investigated as a means of avoiding distortions associated with high power pulse propagation in optical fibres. The results show that it is the interplay between the nonlinear and dispersive effects that leads to stable formation of the self-similar solutions. By considering generalised nonlinear Schrödinger equations we have extended the previous investigations of linearly chirped parabolic pulse solutions, which exist in the normal dispersion regime, and have found a new broader class of self-similar solutions, which exist when the fibre parameters are allowed to vary longitudinally. Numerical simulations of these systems confirm the analytic predictions. Experimental confirmation of parabolic pulse generation in high gain cascaded amplifier systems and in highly nonlinear microstructured fibres is also reported. In addition, the propagation of light in modulated crystal structures has been investigated. By modifying the linear and nonlinear properties of the crystals it has been shown that it is possible to manipulate the speed and the wavelength of the propagating light. In particular, negative refractive index materials have been shown to support fast and/or slow propagating light, whilst two dimensional nonlinear photonic crystals have been used to demonstrate multiple harmonic generation over a wide range of phase matching angles. The influence of waveguiding geometries has also been considered to determine the optimum design for the efficiency of the devices
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Balakrishnan, Nilanthy. "Novel approaches to the fabrication of nanoscale devices." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/50598/.
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This thesis describes the effects of a post-growth hydrogenation on as-grown samples and device structures based on III-N-V and III-V semiconductor compounds. The spectral response of quantum wells (QWs) or superlattices (SLs) are tuned by the control dissociation of N-H complexes using a focused laser beam (photon assisted dissociation) or by thermal annealing. These approaches could be implemented in other materials and heterostructure devices, and offer the advantage of enabling an accurate control of the spectral response of a device using a layer compound with a single N- concentration. A focused laser beam is also used to diffuse hydrogen from the p-type contact layer towards the III-N-V superlattice in the intrinsic region of a p-i-n diode, thus creating preferential injection paths for the carriers and creating nanoscale light emitting diodes. Opportunities for realizing a movable micron size-light emitting diode (-LED) are also demonstrated. Moreover, room temperature electroluminescence from semiconductor junctions formed from combinations of n-InSe, p-InSe, p-GaSe and n-In2O3 is demonstrated. These p-n junctions are fabricated using mechanical exfoliation of Bridgman-grown crystals and a simple mechanical contact method or thermal annealing. These results demonstrate the technological potential of mechanically formed heterojunctions and homojunctions of direct band gap layered GaSe and InSe compounds with an optical response over an extended wavelength range, from the near-infrared to the visible spectrum. These layered crystals could be combined in different sequences of layer stacking, thus offering exciting opportunities for new structures and devices.
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Hung, Ting-Hsiang. "Novel High-k Dielectric Enhanced III-Nitride Devices." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437684419.
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Kawahara, Jun. "Novel architectures for flexible electrochemical devices and systems." Doctoral thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-91273.
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Electrically conducting polymers were discovered in the late 1970s. This finding generated a whole new research area named organic electronics, an area which has attracted great interest and tremendous achievements, in terms of devices and applications, have been reached by different research groups all over the world. Replacing inorganic materials by their organic counterparts in various kinds of electronic devices provides novel device functionalities as well as new opportunities in device manufacturing. One of the major advantages of utilizing organic materials in electronic devices is the high degree of freedom regarding fabrication methods. Since organic materials can be processed from solution various printing, coating and lamination techniques can be used to manufacture entire electronic systems on flexible carriers and substrates in a truly reel-to-reel fashion. The main theme of this thesis relates to exploring novel device architectures to enable easy manufacturing of flexible electrochromic displays based on organic materials. After the introduction, the second part of the thesis treats some of the fundamentals of conducting polymers, and the third part explains the building blocks of matrix-addressed electrochromic displays: those systems combine electrochemical transistors and electrochromic display pixels. A brief introduction to printed electronics is also given in the fourth section. Then, active matrix addressed displays utilizing electronic vias manufactured through the substrate, which enable to use the substrate more efficiently in the resulting three-dimensional architecture, are presented in the fifth section. This novel system arrangement results in a matrix-addressed display with a relatively high fill-factor since its subcomponents are located on opposite sides of the substrate. The sixth section of the thesis is related to the achievement of passive matrix addressed displays. The architecture and the manufacturing process of these electrochromic displays are both very simple: an electrolyte is sandwiched in between the counter and the pixel electrode layers. The electrode materials chosen results in a non-linear current versus voltage characteristics, which enables matrix addressability also without the transistors. At last, in the seventh section, nanofibrillated cellulose (NFC) is used as the scaffold for either an electroactive polymer or the electrolyte. Various components, such as electrochromic pixels and electrochemical transistors, can be built from the resulting solid films thanks to the stable, soft and tacky properties of the hybridized NFC layer. Hence, a new concept for integration and reconfiguration of electronic systems consisting of electrochemical devices is achieved.
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Jiang, Zhe. "Novel nanowire structures and devices for nanoelectronic bioprobes." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467307.
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Semiconductor nanowire materials and devices provide unique opportunities in the frontier between nanoelectronics and biology. The bottom-up paradigm enables flexible synthesis and patterning of nanoscale building blocks with novel structures and properties, and nano-to-micro fabrication methods allow the advantages of functional nanowire elements to interface with biological systems in new ways. In this thesis, I will focus on the development of bottom-up nanoscience platforms, which includes rational synthesis and assembly of semiconductor nanowires with new capabilities, as well as design and fabrication of the first free-standing three-dimensional (3D) nanoprobes, with special focus on applications in intracellular recording and stimulation.
I will first introduce kinked p-n junction nanowires as a new and powerful family of high spatial resolution biological and chemical sensors with proof-of-concept applications. Next, I will discuss a variety of functional kinked nanowires with synthetically controlled properties and the potential of achieving more detailed and less invasive cellular studies. Furthermore, I will present a general shape-controlled deterministic nanowire assembly method to produce large-scale arrays of devices with well-defined geometry and position.
Then, I will present the design of a general method to fabricate these nanowire structures into free-standing 3D probes. I will show that free-standing nanowire bioprobes can be manipulated to target specific cells and record stable intracellular action potentials. I will demonstrate simultaneous measurements from the same cell using both kinked nanowire and patch-clamp probes. Moreover, I will discuss two strategies of multiplexed recording using free-standing probes.
Finally, I will report localized stimulation on single cells enabled by the unique properties of p-n kinked nanowires. I will show with simulation and electrical characterization that in reverse bias, localized electric field generated around the nanoscale p-n junction should exceed the threshold for opening voltage-gated sodium channels. Moreover, I will present measurements of localized cell stimulation using p-n nanowire free-standing probes. Together with the capability of stable intracellular recording, these results complete the two-way communication between semiconductor nanowire electronics and biological systems at a natural nanoscale, which can open up new directions in the fields ranging from cellular electrophysiology, brain activity mapping to brain-machine interface.Chemistry and Chemical Biology
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Ng, Ka Fai. "Novel low power CAM architecture /." Online version of thesis, 2008. http://hdl.handle.net/1850/7771.
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