Quantitative Transmission Electron Microscopy Study of III-Nitride Semiconductor Nanostructures PDF Download
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Author: Maxim Korytov
Publisher:
ISBN:
Category :
Languages : en
Pages : 180
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Book Description
The theoretical part of this thesis is dedicated to the adaptation of high-resolution transmission electron microscopy (HRTEM) for the study of GaN-based materials. First, the principle of heterostructure composition evaluation by means of the relative atomic displacement measurement is stated. The comparison of two strain measurement techniques, geometric phase analysis and projection method, is then presented. Finally, the effects of acquisition conditions on strain measurements were studied. The experimental part of this thesis is dedicated to the characterization of GaN quantum dots (QDs) realized on Al0.5Ga0.5N templates. This study revealed several phenomena original for nitride semiconductors. The surface QD shape changes from perfect pyramidal to truncated pyramidal with the increase of the nominal thickness of the deposited GaN layer. The capping of QDs having a perfect pyramidal shape leads to a QD shape truncation and a QD volume increase. Moreover, a phase separation was found in the AlGaN barriers with Al-rich zones formed above the QDs and Ga-rich regions placed around the Al-rich zones. The Al concentration into the Al-rich zones is about 70% and it decreases as the distance from the QD increases. To explain the observed phenomena, various models founded on the principle of total energy minimization have been developed. Several approaches, based on the results of this study and aimed for the improvement of the optoelectronic devices properties, are proposed.
Author: Maxim Korytov
Publisher:
ISBN:
Category :
Languages : en
Pages : 180
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Book Description
The theoretical part of this thesis is dedicated to the adaptation of high-resolution transmission electron microscopy (HRTEM) for the study of GaN-based materials. First, the principle of heterostructure composition evaluation by means of the relative atomic displacement measurement is stated. The comparison of two strain measurement techniques, geometric phase analysis and projection method, is then presented. Finally, the effects of acquisition conditions on strain measurements were studied. The experimental part of this thesis is dedicated to the characterization of GaN quantum dots (QDs) realized on Al0.5Ga0.5N templates. This study revealed several phenomena original for nitride semiconductors. The surface QD shape changes from perfect pyramidal to truncated pyramidal with the increase of the nominal thickness of the deposited GaN layer. The capping of QDs having a perfect pyramidal shape leads to a QD shape truncation and a QD volume increase. Moreover, a phase separation was found in the AlGaN barriers with Al-rich zones formed above the QDs and Ga-rich regions placed around the Al-rich zones. The Al concentration into the Al-rich zones is about 70% and it decreases as the distance from the QD increases. To explain the observed phenomena, various models founded on the principle of total energy minimization have been developed. Several approaches, based on the results of this study and aimed for the improvement of the optoelectronic devices properties, are proposed.
Author: Andreas Rosenauer
Publisher: Springer
ISBN: 3540364072
Category : Science
Languages : en
Pages : 238
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Book Description
This book provides tools well suited for the quantitative investigation of semiconductor electron microscopy. These tools allow for the accurate determination of the composition of ternary semiconductor nanostructures with a spatial resolution at near atomic scales. The book focuses on new methods including strain state analysis as well as evaluation of the composition via the lattice fringe analysis (CELFA) technique. The basics of these procedures as well as their advantages, drawbacks and sources of error are all discussed. The techniques are applied to quantum wells and dots in order to give insight into kinetic growth effects such as segregation and migration. In the first part of the book the fundamentals of transmission electron microscopy are provided. These are needed for an understanding of the digital image analysis techniques described in the second part of the book. There the reader will find information on different methods of composition determination. The third part of the book focuses on applications such as composition determination in InGaAs Stranski--Krastanov quantum dots. Finally it is shown how an improvement in the precision of the composition evaluation can be obtained by combining CELFA with electron holography. This is demonstrated for an AlAs/GaAs superlattice.
Author: Eirini Sarigiannidou
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
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Book Description
In this thesis we present the structural characterization of GaN/AIN quantum wells (QWs) and quantum dots (QDs) grown by plasma assisted molecular beam epitaxy. The technique we use is the transmission electron microscopy in (i) high resolution, (ii) energy filtered, (Hi) conventional and (iv) convergent beam modes. The quantitative analysis of our nanostructures is realized using a projection method and the geometric phase analysis. In order to obtain the most accurate results those methods are optimized and specific experimental conditions, like off-axis HRTEM images, are applied. A comparison study between a Ga-face and a N-face GaN/AIN superlattice (SL) is presented and the higher structural quality (the Ga-face SL is proven: abrupt and uniform interfaces, absence of inversion domain boundaries and partially strained QWs. We also analyze the effects of AIN overgrowth on the structural quality of GaN nanostructures. We show that the overgrowth process implies a thinning of the GaN QWs and an isotropic reduction of the GaN QDs size. The phenomenon is attributed to an exchange mechanism between AI atoms from the cap layer and Ga atoms in the nanostructures. We investigate the strain distribution in a GaN/AIN QD superlattice. Using HRTEM, theoretical calculations and X-ray diffraction experiments we demonstrate that the vertical alignment of the QDs is due to a modulation of the strain state of the AIN layers. Finally, we examine the polytype conversion of a GaN film from N-face wurtzite to zinc-blende structure due to Mg high doping.
Author: Korytov-M
Publisher: Omn.Univ.Europ.
ISBN: 9786131545009
Category : Literary Criticism
Languages : en
Pages : 196
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Book Description
The theoretical part of this work is dedicated to the adaptation of high-resolution transmission electron microscopy for studying III-nitride semiconductors. First, the principle of heterostructure composition evaluation by means of atomic displacement measurement is stated. The comparison of two strain measurement techniques, geometric phase analysis and projection method, is then presented. Finally, the effects of acquisition conditions on the strain measurements were elaborated. The experimental part of this work is dedicated to the characterization of GaN quantum dots (QDs) grown on AlGaN templates. This study revealed several phenomena original for nitride semiconductors. The surface QD shape depends on the GaN layer thickness, whereas the buried QD shape and volume are influenced by the QD capping. Moreover, a phase separation occurs in the AlGaN barriers. To explain the observed phenomena, various models founded on the principle of total energy minimization have been developed. Several approaches, based on the results of this study and aimed for the improvement of the optoelectronic devices properties, are also proposed.
Author: 張文明
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Andreas Rosenauer
Publisher:
ISBN: 9783662146170
Category :
Languages : en
Pages : 256
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Author: 李仁宏
Publisher:
ISBN:
Category :
Languages : en
Pages : 117
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Author: Alina Bruma
Publisher: CRC Press
ISBN: 0429516169
Category : Technology & Engineering
Languages : en
Pages : 162
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Book Description
Scanning Transmission Electron Microscopy: Advanced Characterization Methods for Materials Science Applications The information comprised in this book is focused on discussing the latest approaches in the recording of high-fidelity quantitative annular dark-field (ADF) data. It showcases the application of machine learning in electron microscopy and the latest advancements in image processing and data interpretation for materials notoriously difficult to analyze using scanning transmission electron microscopy (STEM). It also highlights strategies to record and interpret large electron diffraction datasets for the analysis of nanostructures. This book: Discusses existing approaches for experimental design in the recording of high-fidelity quantitative ADF data Presents the most common types of scintillator-photomultiplier ADF detectors, along with their strengths and weaknesses. Proposes strategies to minimize the introduction of errors from these detectors and avenues for dealing with residual errors Discusses the practice of reliable multiframe imaging, along with the benefits and new experimental opportunities it presents in electron dose or dose-rate management Focuses on supervised and unsupervised machine learning for electron microscopy Discusses open data formats, community-driven software, and data repositories Proposes methods to process information at both global and local scales, and discusses avenues to improve the storage, transfer, analysis, and interpretation of multidimensional datasets Provides the spectrum of possibilities to study materials at the resolution limit by means of new developments in instrumentation Recommends methods for quantitative structural characterization of sensitive nanomaterials using electron diffraction techniques and describes strategies to collect electron diffraction patterns for such materials This book helps academics, researchers, and industry professionals in materials science, chemistry, physics, and related fields to understand and apply computer-science–derived analysis methods to solve problems regarding data analysis and interpretation of materials properties.
Author: Zhe Chuan Feng
Publisher: World Scientific
ISBN: 1786343207
Category : Science
Languages : en
Pages : 424
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Book Description
Group III-Nitrides semiconductor materials, including GaN, InN, AlN, InGaN, AlGaN and AlInGaN, i.e. (Al, In, Ga)N, are excellent semiconductors, covering the spectral range from deep ultraviolet (DUV) to UV, visible and infrared, with unique properties very suitable for modern electronic and optoelectronic applications. Remarkable breakthroughs have been achieved in recent years for research and development (R&D) in these materials and devices, such as high-power and high brightness UV-blue-green-white light emitting diodes (LEDs), UV-blue-green laser diodes (LDs), photo-detectors and various optoelectronics and electronics devices and applications.The Nobel Prize in Physics 2014 was awarded jointly to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura 'for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources'. Red and green diodes had been invented since 1960s-70s but without blue LED. Despite considerable efforts, the blue LED had remained a challenge for a long time. The success and inventions on GaN-based LEDs were revolutionary and benefiting for mankind. III-Nitrides-based industry has formed and acquired rapid developments over the world. Incandescent light bulbs lit the 20th century and the 21st century will be lit by LED lamps.Before this book, the editor has edited two books, III-Nitride Semiconductor Materials (2006) and III-Nitride Devices and Nanoengineering (2008), both published by ICP/WSP, in the fields of III-Nitride. The developments of these materials and devices are moving rapidly. Many data or knowledge, some even just published only recently, have been modified and needed to be upgraded. This new book, III-Nitride Materials, Devices and Nano-Structures as the third instalment, will cover the rapid new developments and achievements in the III-Nitride fields, particularly those made since 2009.
Author: Chun Maw Tey
Publisher:
ISBN:
Category :
Languages : en
Pages :
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