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Zirconium-doped tantalum oxide high-k gate dielectric filmsTewg, Jun-Yen 17 February 2005 (has links)
A new high-k dielectric material, i.e., zirconium-doped tantalum oxide (Zr-doped TaOx), in the form of a sputter-deposited thin film with a thickness range of 5-100 nm, has been studied. Important applications of this new dielectric material include the gate dielectric layer for the next generation metal-oxide-semiconductor field effect transistor (MOSFET). Due to the aggressive device scaling in ultra-large-scale integrated circuitry (ULSI), the ultra-thin conventional gate oxide (SiO2) is unacceptable for many practical reasons. By replacing the SiO2 layer with a high dielectric constant material (high-k), many of the problems can be solved. In this study, a novel high-k dielectric thin film, i.e., TaOx doped with Zr, was deposited and studied. The films electrical, chemical, and structural properties were investigated experimentally. The Zr dopant concentration and the thermal treatment condition were studied with respect to gas composition, pressure, temperature, and annealing time. Interface layer formation and properties were studied with or without an inserted thin tantalum nitride (TaNx) layer. The gate electrode material influence on the dielectric properties was also investigated. Four types of gate materials, i.e., aluminum (Al), molybdenum (Mo), molybdenum nitride (MoN), and tungsten nitride (WN), were used in this study. The films were analyzed with ESCA, XRD, SIMS, and TEM. Films were made into MOS capacitors and characterized using I-V and C-V curves. Many promising results were obtained using this kind of high-k film. It is potentially applicable to future MOS devices.
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Zirconium-doped tantalum oxide high-k gate dielectric filmsTewg, Jun-Yen 17 February 2005 (has links)
A new high-k dielectric material, i.e., zirconium-doped tantalum oxide (Zr-doped TaOx), in the form of a sputter-deposited thin film with a thickness range of 5-100 nm, has been studied. Important applications of this new dielectric material include the gate dielectric layer for the next generation metal-oxide-semiconductor field effect transistor (MOSFET). Due to the aggressive device scaling in ultra-large-scale integrated circuitry (ULSI), the ultra-thin conventional gate oxide (SiO2) is unacceptable for many practical reasons. By replacing the SiO2 layer with a high dielectric constant material (high-k), many of the problems can be solved. In this study, a novel high-k dielectric thin film, i.e., TaOx doped with Zr, was deposited and studied. The films electrical, chemical, and structural properties were investigated experimentally. The Zr dopant concentration and the thermal treatment condition were studied with respect to gas composition, pressure, temperature, and annealing time. Interface layer formation and properties were studied with or without an inserted thin tantalum nitride (TaNx) layer. The gate electrode material influence on the dielectric properties was also investigated. Four types of gate materials, i.e., aluminum (Al), molybdenum (Mo), molybdenum nitride (MoN), and tungsten nitride (WN), were used in this study. The films were analyzed with ESCA, XRD, SIMS, and TEM. Films were made into MOS capacitors and characterized using I-V and C-V curves. Many promising results were obtained using this kind of high-k film. It is potentially applicable to future MOS devices.
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Properties And Applications Of Semiconductor And Layered NanomaterialsChitara, Basant 03 1900 (has links) (PDF)
This thesis deals with the research work carried out on the properties and applications such as GaN nanoparticles, Graphene etc.
Chapter 1 of the thesis gives introduction to nanomaterials and various aspects of the thesis. Chapter 2 of the thesis describes the synthesis of GaN nanocrystals and their use as white light sources and as room temperature gas sensors. It also discusses negative differential resistance above room temperature exhibited by GaN. Electroluminescence from GaN-polymer heterojunction forms the last section of this chapter. Chapter 3 demonstrates the role of defect concentration on the photodetecting properties of ZnO nanorods with different defects prepared at different temperatures. Chapter 4 presents remarkable infrared and ultraviolet photodetector properties of reduced graphene oxide and graphene nanoribbons. Chapter 5 presents the infrared detecting properties of graphene-like few-layer MoS2.
The summary of the thesis is given at the end of the thesis.
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Thermal stability of plasma enhanced chemical vapor deposited silicon nitride thin filmsJehanathan, Neerushana January 2007 (has links)
[Truncated abstract] This study investigates the thermal stability of Plasma Enhanced Chemical Vapor Deposited (PECVD) silicon nitride thin films. Effects of heat-treatment in air on the chemical composition, atomic bonding structure, crystallinity, mechanical properties, morphological and physical integrity are investigated. The chemical composition, bonding structures and crystallinity are studied by means of X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) Spectroscopy and Transmission Electron Microscopy (TEM). The mechanical properties, such as hardness and Young’s modulus, are determined by means of nanoindentation. The morphological and physical integrity are analyzed using Scanning Electron Microscopy (SEM) . . . The Young’s modulus (E) and hardness (H) of the film deposited at 448 K were measured to have E=121±1.8 GPa and H=11.7±0.25 GPa. The film deposited at 573 K has E=150±3.6 GPa and H=14.7±0.6 GPa. For the film deposited at 573 K, the Young’s modulus is not affected by heating up to 1148 K. Heating at 1373 K caused significant increase in Young’s modulus to 180∼199 GPa. This is attributed to the crystallization of the film. For the film deposited at 448 K, the Young’s modulus showed a moderate increase, by ∼10%, after heating to above 673 K. This is consistent with the much lower level of crystallization in this film as compared to the film deposited at 573 K. In summary, low temperature deposited PECVD SiNx films are chemically and structurally unstable when heated in air to above 673 K. The main changes include oxidation to SiO2, crystallization of Si3N4 and physical cracking. The film deposited at 573 K is more stable and damage and oxidation resistant than the film deposited at 448 K.
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Influência do teor de silício em filmes finos de nitreto de zircônio depositados por magnetron sputtering reativo / Influence of silicon content in zirconium nitride thin films deposited by reactive magnetron sputteringFreitas, Flávio Gustavo Ribeiro 19 March 2016 (has links)
Zr-Si-N thin films were deposited by reactive magnetron sputtering to study silicon
influence in the structure, morphology and properties such as hardness and oxidation
resistance. Six thin films with silicon concentrations from 2.8 to 14.9 at.% were
selected. Thin films morphology shows that there are no columnar grains, structure that
is commonly observed in films deposited by sputtering. It was identified amorphous and
crystalline areas in films microstructure, creating a structure composed by crystalline
grains embedded in an amorphous phase, which were characterized by EDS as Zr and Si
rich areas, respectively. XRD results indicate ZrN peaks intensity reduction and a
broadening increase due silicon nitride segregation to grain boundaries, which is
responsible for grain size reduction, that was calculated by Scherrer and reached
magnitudes lower than 10 nm. XRD peaks displacement are observed for all samples
and it can be explained due formation of a solid solution in which Si replaces Zr atoms
in ZrN crystal lattice and due a strong interface between crystalline phase and
amorphous one. XPS data reinforce the presence of compounds like ZrN and Si3N4 and
it is also possible to infer the formation of a solid solution of Si in ZrN lattice.
Oxidation tests were performed at temperatures in the range of 500°C to 1100°C. ZrN
film is almost fully oxidized at 500°C, while films with high silicon content maintain
ZrN grains stable at 700°C. When oxidized, ZrN films form monoclinic ZrO2 phase,
but, in films with silicon addition, the stable phase is the tetragonal one. This happens
due ZrN grain size reduction, because tetragonal phase has the lowest surface energy.
Oxidation tests results confirm that there is a mechanism acting as diffusion barrier in
films, preventing grains coalescence and oxygen diffusion into film structure. This
mechanism is a direct consequence of silicon segregation process to grain boundaries,
which ensures the formation of a nanostructure composed of ZrN grains embedded by
an amorphous Si3N4 layer (nc-ZrN/a-Si3N4), allowing oxidation resistance improvement
in at least 200°C. / Filmes finos de Zr-Si-N foram depositados por magnetron sputerring reativo para
estudar a influência do teor de silício na estrutura, morfologia e propriedades como
dureza e resistência a oxidação. Para tal, foram selecionados seis filmes com teor de Si
entre 2,8 e 14,9 at.%. A morfologia demonstra que a estrutura colunar característica dos
filmes depositados por sputtering não existe. A estrutura é composta por áreas
cristalinas e outras amorfas, na qual os grãos cristalinos estão envolvidos pela fase
amorfa, sendo que EDS detectou que estas fases são ricas em Zr e Si, respectivamente.
Há redução de intensidade e alargamento dos picos de difração do ZrN, efeito
provocado pela segregação do Si3N4 para região dos contornos, fato que propicia a
redução do tamanho de grão, o qual foi calculado por Scherrer e atinge magnitude
inferior a 10 nm. Os picos do DRX estão deslocados, fato justificado pela formação de
uma solução sólida na qual o Si substituiu o Zr no reticulado do ZrN e pela forte
interface formada entre as fases cristalina e amorfa. Dados de XPS reforçam a formação
de uma estrutura bifásica de ZrN e Si3N4 e mostra indícios de que há uma solução sólida
de Si no ZrN. Os ensaios de oxidação foram realizados em temperaturas de 500°C até
1100°C. O filme de ZrN praticamente se oxida a 500°C, enquanto nos filmes com altos
teores de silício os grãos de ZrN se mantém estáveis até 700°C. Quando oxidado, os
filmes de ZrN formam predominantemente ZrO2 na fase monoclínica, mas, nos filmes
com adição de Si há a inversão para a fase tetragonal. Tal fato é fruto da redução do
tamanho de grão, pois a fase tetragonal possui menor energia de superfície. Tais
resultados ratificam que existe mecanismo atuando como barreira a difusão, o qual
impede a coalescência dos grãos e a difusão do oxigênio. Este mecanismo é resultado
do processo de segregação do silício para os contornos, o qual assegura a formação da
nanoestrutura composta de grãos de ZrN embebidos por camada amorfa de Si3N4 (nc-
ZrN/a-Si3N4) e permite aprimorar a resistência a oxidação em pelo menos 200°C.
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Optical studies of InGaN/GaN quantum well structuresDavies, Matthew John January 2014 (has links)
In this thesis I present and discuss the results of optical spectroscopy performed on InGaN/GaN single and multiple quantum well (QW) structures. I report on the optical properties of InGaN/GaN single and multiple QW structures, measured at high excitation power densities. I show a correlation exists between the reduction in PL efficiency at high excitation power densities, the phenomenon so-called ``efficiency-droop'', and a broadening of the PL spectra. I also show a distinct change in recombination dynamics, measured by time-resolved photoluminescence (PL), which occurs at the excitation power densities for which efficiency droop is measured. The broadening of the PL spectra at high excitation power densities is shown to occur due to a rapidly redshifting, short-lived high energy emission band. The high energy emission band is proposed to be due to the recombination of weakly localised/delocalised carriers occurring as a consequence of the progressive saturation of the local potential fluctuations responsible for carrier localisation, at high excitation power densities. I report on the effects of varying threading dislocation (TD) density on the optical properties of InGaN/GaN multiple QW structures. No systematic relationship exists between the room temperature internal quantum efficiency (IQE) and the TD density, in a series of nominally identical InGaN/GaN multiple QWs deposited on GaN templates of varying TD density. I also show the excitation power density dependence of the PL efficiency, at room temperatures, is unaffected for variation in the TD density between 2 x107 and 5 x109 cm-2. The independence of the optical properties to TD density is proposed to be a consequence of the strong carrier localisation, and hence short carrier diffusion lengths. I report on the effects of including an InGaN underlayer on the optical and microstructural properties of InGaN/GaN multiple QW structures. I show an increase in the room temperature IQE occurs for the structure containing the InGaN underlayer, compared to the reference. I show using PL excitation spectroscopy that an additional carrier transfer and recombination process occurs on the high energy side of the PL spectrum associated with the InGaN underlayer. Using PL decay time measurements I show the additional recombination process for carriers excited in the underlayer occurs on a faster timescale than the recombination at the peak of the PL spectrum. The additional contribution to the spectrum from the faster recombination process is proposed as responsible for the increase in room temperature IQE.
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Měřicí doteky ve strojírenské metrologii / Measuring probe tips in engineering metrologyBöhm, Jakub January 2018 (has links)
This diploma thesis deals with measuring touches problems in industrial metrology. Thesis describes adhesive wear and tear which is caused by measuring probes when dynamical measuring is being concluded. Measuring of damaged component made of silumin and its different changes of texture by different measuring probes are evaluated. Measuring touches are made of titanium nitride, silicon nitride, zirconium, bearing chrome steel, ruby, experimental composite material and nanocrystalline diamond.
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Micro-Raman Spectroskopy Investigation of Hard CoatingsWerninghaus, Thomas 01 July 1997 (has links)
Abstract: MicroRaman Spectroscopy Investigation of Hard Coatings
Diamond, silicon carbide, and boron nitride have attracted great interest in the last years, due
to their excellent material properties. Especially the extreme hardness and the high thermal con
ductivity of these materials favour them as protective layers. The very large hardness gave these
materials, deposited as films on various substrates, their name: hard coatings. In contrast to di
amond, silicon carbide and boron nitride can be n as well as pdoped, making them promising
candidates for high speed and high temperature electronic applications. Contrarily to the materials
mentioned above, carbon nitride was obtained in crystalline form just very recently. Up to now the
deposited films mainly consist of amorphous or nanocrystalline, carbonrich material. For all these
material systems inelastic light scattering (Raman spectroscopy) has been already applied for the
material properties investigation. However, these investigations usually were restricted to only one
of the various Raman spectroscopy tools, described in this work: Incident laser light energy varia
tion, temperature variation, utilizing the selection rules, measurements at varying sample positions,
twodimensional mappings and onedimensional scans in the conventional planeview and the addi
tional crosssectional sample geometry. In contrast to this, this work demonstrates the improvement
of the information about the investigated material and/or the sample heterostructure obtained by
using the combination of all the above mentioned techniques. In the case of the diamond material
system, films deposited on silicon substrates were investigated and an interfacial graphitic layer
of 2nm thickness was found by scanning across the interface, which was obscured in the conven
tional planeview sample geometry. Similar to this an ultrathin top layer and buried intermixed
regions were identified in the silicon carbide material system utilizing the crosssectional sample
geometry. In addition to this, the temperature and the incident laser light energy dependences for
5 SiC polytypes (3C, 4H, 6H, 15R, and 21R) were measured. A resonance enhancement for the
3C and the 21R polytype was found corresponding to their fundamental bandgaps at 2.46eV and
ß2.8eV, respectively. For the other polytypes no resonance enhancement was found, due to their
larger fundamental bandgap. In the boron nitride material system the spatial correlation model for
Raman lineshape analysis was applied for the first time and the values of the asymmetric broad
ening and the frequency downshift for decreasing crystal sizes were evaluated. This was measured
for single crystals of different size and for films deposited on silicon substrates. The correlation
lengths in the ten nanometer region found for the deposited films corroborate the nanocrystalline
nature of these films. Additionally incident laser light energy was measured, revealing the 488.0nm
(Ar + ) and 482.5nm (Kr + ) laser lines as the optimum laser lines for the boron nitride investigation.
Furthermore the dependence of the phonon feature parameters was investigated depending on the
incident laser light power. A maximum power of 510mW for the microRaman spectroscopy setup
was found to avoid any laser light induced heating of the investigated material. Twodimensional
mappings of the deposited boron nitride films were performed to improve the information about
the material system. In the case of carbon nitride for the first time distinct phonon features were
measured in a wide spectral range contrarily to most of the other investigations, which usually show
only broad bands.
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Intercalation von Stickstoff und Wasserstoff in Sr2N sowie ortsabhängige Feststoffcharakterisierung mit LaserablationChemnitzer, René 12 April 2006 (has links)
Die Strukturen der Erdalkalimetall-Subnitride (EA2N) von Calcium, Strontium und Barium ermöglichen mit ihrem schichtartigen Aufbau aus EA6N-Oktaedern Intercalationsreaktionen. Die Redox-Intercalation von Stickstoff in Sr2N wurde an Einkristallen untersucht. Nur durch eine drastische Erhöhung des Reaktionsgasdruckes im Vergleich zu den Reaktionen an mikrokristallinen Proben wurde die Intercalation der Diazenidionen in die Kristalle zu Sr4N3 und SrN möglich. Für eine analoge Intercalation von Wasserstoff in Sr2N konnten die Reaktionsbedingungen dahingehend optimiert werden, dass erstmals phasenreines Strontiumnitridhydrid (Sr2N)H bzw. deuterid (Sr2N)D erhalten wurde. Anhand von Intercalationsreaktionen mit Sr2N Kristallen konnte gezeigt werden, dass der Intercalationsprozess, erkennbar an der deutlichen Farbänderung von schwarz nach bersteinfarben, von außen nach innen fortschreitet. Als Methode zur räumlich aufgelösten Analyse wurde die Laserablation, in Kombination mit einem ICP - Massenspektrometer (LA-ICP-MS) verwendet. In der Literatur beschriebene Quantifizierungsstrategien wurden auf die Anwendbarkeit für die gegebene Fragestellung untersucht. Mit der ortsaufgelösten Analyse von Einkristallen konnte gezeigt werden, dass die Intercalation von Stickstoff in die Kristalle kontinuierlich von den Kanten zur Kristallmitte fortschreitet.
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Scanned Probe Spectroscopy of Traps in Cross-Sectioned AlGaN/GaN DevicesGleason, Darryl A. 04 September 2019 (has links)
No description available.
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