Optoelectronics Materials and Techniques Part 1 pptx

Contents Preface IX Part 1 Inorganic Optoelectronic Materials 1 Chapter 1 Optoelectronic Properties of Amorphous Silicon the Role of Hydrogen: from Experiment to Modeling 3 Franco Ga

OPTOELECTRONICS -

MATERIALS AND

TECHNIQUES Edited by Padmanabhan Predeep

Optoelectronics - Materials and Techniques

Edited by Padmanabhan Predeep

Published by InTech

Janeza Trdine 9, 51000 Rijeka, Croatia

Copyright © 2011 InTech

All chapters are Open Access articles distributed under the Creative Commons

Non Commercial Share Alike Attribution 3.0 license, which permits to copy,

distribute, transmit, and adapt the work in any medium, so long as the original

work is properly cited After this work has been published by InTech, authors

have the right to republish it, in whole or part, in any publication of which they

are the author, and to make other personal use of the work Any republication,

referencing or personal use of the work must explicitly identify the original source Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher No responsibility is accepted for the accuracy of information contained in the published articles The publisher assumes no responsibility for any damage or injury to persons or property arising out

of the use of any materials, instructions, methods or ideas contained in the book

Publishing Process Manager Mirna Cvijic

Technical Editor Teodora Smiljanic

Cover Designer Jan Hyrat

Image Copyright Triff, 2010 Used under license from Shutterstock.com

First published September, 2011

Printed in Croatia

A free online edition of this book is available at www.intechopen.com

Additional hard copies can be obtained from orders@intechweb.org

Optoelectronics - Materials and Techniques, Edited by Padmanabhan Predeep

p cm

ISBN 978-953-307-276-0

free online editions of InTech

Books and Journals can be found at

www.intechopen.com

Contents

Preface IX

Part 1 Inorganic Optoelectronic Materials 1

Chapter 1 Optoelectronic Properties of Amorphous Silicon

the Role of Hydrogen: from Experiment to Modeling 3

Franco Gaspari

Chapter 2 Silicon–Rich Silicon Oxide Thin Films Fabricated

by Electro-Chemical Method 27

Pham Van Hoi, Do Thuy Chi, Bui Huy and Nguyen Thuy Van

Chapter 3 Silicon Oxide (SiO x , 0<x<2):

a Challenging Material for Optoelectronics 55

Nicolae Tomozeiu

Chapter 4 Gallium Nitride: An Overview of Structural Defects 99

Fong Kwong Yam, Li Li Low, Sue Ann Oh, and Zainuriah Hassan Chapter 5 Cuprous Oxide (Cu 2 O): A Unique System Hosting

Various Excitonic Matter and Exhibiting Large Third-Order Nonlinear Optical Responses 137

Joon I Jang

Chapter 6 Optoelectronic Properties

of ZnSe, ITO, TiO 2 and ZnO Thin Films 165

S Venkatachalam, H Nanjo, K Kawasaki,

H Hayashi, T Ebina and D Mangalaraj

Part 2 Polymer Optoelectronic Materials 185

Chapter 7 Side-Chain Multifunctional

Photoresponsive Polymeric Materials 187

Luigi Angiolini, Tiziana Benelli, Loris Giorgini, Attilio Golemme, Elisabetta Salatelli and Roberto Termine

VI Contents

Chapter 8 Ladder Polysiloxanes

for Optoelectronic Applications 211

Zhongjie Ren, Shouke Yan and Rongben Zhang Chapter 9 Synthesis of Aromatic-Ring-Layered Polymers 235

Yasuhiro Morisaki and Yoshiki Chujo Chapter 10 Nanomorphologies in Conjugated Polymer Solutions

and Films for Application in Optoelectronics, Resolved by Multiscale Computation 261

Cheng K Lee and Chi C Hua

Part 3 Techniques and Characterization 285

Chapter 11 Optoelectronic Techniques

for Surface Characterization of Fabrics 287

Michel Tourlonias, Marie-Ange Bueno and Laurent Bigué

Chapter 12 Optoelectronic Circuits

for Control of Lightwaves and Microwaves 313

Takahide Sakamoto Chapter 13 An Analytical Solution for Inhomogeneous

Strain Fields Within Wurtzite GaN Cylinders Under Compression Test 337

X X Wei Chapter 14 Application of Quaternary AlInGaN- Based Alloys

for Light Emission Devices 355

Sara C P Rodrigues, Guilherme M Sipahi,

Luísa Scolfaro and Eronides F da Silva Jr

Chapter 15 Air Exposure Improvement of Optical Properties

of Hydrogenated Nanostructured Silicon Thin Films for Optoelectronic Application 375

Atif Mossad Ali Chapter 16 Fabrication and Characterization of As Doped

p-Type ZnO Films Grown by Magnetron Sputtering 393

J.C Fan, C.C Ling and Z Xie Chapter 17 Light Intensity Fluctuations and Blueshift 421

Moon Kyu Choi Chapter 18 Self-Similarity in Semiconductors:

Electronic and Optical Properties 435

L M Gaggero-Sager, E Pujals,

D S Díaz-Guerrero and J Escorcia-García

Chapter 19 Long-Term Convergence

of Bulk- and Nano-Crystal Properties 459

Sergei L Pyshkin and John Ballato

Chapter 20 Micro-Raman Studies

of Li Doped and Undoped ZnO Needle Crystals 477

R Jothilakshmi

To my father; but for his unrelenting efforts I would not have made it to this day

Preface

Optoelectronics - Materials and Techniques is the first part of an edited anthology on

the multifaceted areas of optoelectronics contributed by a selected group of authors including promising novices to experts in the field, where are discussed related materials and techniques Photonics and optoelectronics are making an impact multiple times the semiconductor revolution made on the quality of our life In telecommunication, entertainment devices, computational techniques, clean energy harvesting, medical instrumentation, materials and device characterization and scores

of other areas of R&D the science of optics and electronics get coupled by fine technology advances to make incredibly large strides The technology of light has advanced to a stage where disciplines sans boundaries are finding it indispensable In this context this book would be of importance to researchers from materials scientists

to device designers and fabricators

Photonics is to optics like electronics is to electricity Photonics sculpts light like a sculptor does with granite Light is beings squeezed, cut into the pieces, reconstructed back and the like Currently optics is undergoing revolutionary changes and photonics

is going to be the next centuries’ technology Globally, countries are vying with each other in formulating their technology initiatives so as to ensure that they should not miss the “Photonics Bus” as many of them missed the semiconductor revolution in the last century Data transfer and communication technology are going to unimaginable heights by the idea of photonic crystals - the idea optical scientists copied from mother nature’s work in nanotechnology in blooming beautiful colors and patterns on objects

of desire like butterfly wings and peacock feathers

With the emergence of photonics and laser technology, optoelectronics seems to be losing its identity and is often mixed up with photonics Photonics draws from and contributes to several other fields, such asquantum electronicsand modern optics In this era of great mix up of disciplines and multidisciplinary research, it is not surprising that such mix of closely connected players like electrons and photons refuses to be confined to narrow boundaries of sub disciplines Naturally the articles in this anthology also have their boundaries diffused over the diverse optical phenomena

of optoelectronics and photonics Readers are advised to bear this in mind when looking for titles of this book

X Preface

I am proud to present this collection of carefully selected peer reviewed high quality articles on various optoelectronic and photonic materials and techniques and would like to thank to the authors for their wonderful efforts Stake holders of the ongoing optoelectronic and photonics revolution such as researchers, academics and scientists are sure to find this collection of essays enormously useful

July 2011

P Predeep

Professor Laboratory for Unconventional Electronics & Photonics

Department of Physics National Institute of Technology Calicut

India

Part 1

Inorganic Optoelectronic Materials

1

Optoelectronic Properties of Amorphous Silicon

the Role of Hydrogen: From Experiment to Modeling

However, the presence of metastable defects in a-Si:H adversely affects the performance of photovoltaic cells and thin film transistors Electrical conductivity, photoconductivity and luminescence degradation have been linked to defect formation, such as dangling bonds (DBs) in the a-Si:H film (Akkaya & Aktas, 1995; Street, 1980)

Staebler and Wronski (1977) found that defects can be created by illuminating a-Si:H The creation of these light-induced defects (LID) is therefore referred to as the Staebler-Wronski (SW) effect The presence of these defects, or dangling bonds, is the major factor responsible for the deterioration of the optical and electronic properties of a-Si:H On the other hand, these defects are metastable and can be cured Indeed, we could define a SW process that can be described as a two-step reversible process:

i Exposure to sunlight leads to an increase in the density of states (dangling bonds) in the energy gap of a-Si:H; this represents the SW effect proper;

ii Subsequent annealing at elevated temperatures (150-200 OC) reduces the density of states back to the original value, thus restoring the optoelectronic properties

It has been shown experimentally that both optical and electronic properties of amorphous silicon, such as refractive index, optical gap, absorption coefficient, electron and hole

Optoelectronics - Materials and Techniques

4

mobility, etc., are strongly dependent on hydrogen content, in terms of both hydrogen concentration and hydrogen dynamics (diffusion) under various conditions - see, for instance, (Searle, 1998) and references therein The investigation of such dynamics, including the relation with defect creation and annealing, is crucial for assessing the appropriate solutions to achieve better control of the defects and, consequently, better optoelectronic performances

There exists a large amount of articles and review papers or books that address the basic properties of a-Si:H, including analysis of the structural, optical and electronic properties; description of a variety of experimental methods used for the growth of a-Si:H films; and correlation between growth parameters and film quality

In this chapter a summary of the basic properties and historical issues related to a-Si:H and its applications in optoelectronics is presented in section 2 A more exhaustive description of the basic properties of a-Si:H is provided by the references in this section Section 3 will focus on the role of hydrogen in relation to the optoelectronic properties and defect dynamics in a-Si:H, and will examine some of the prominent models of hydrogen diffusion also used to describe the SW process dynamics Section 4 will describe the use of tritium, an isotope of hydrogen, as an experimental probe that can be used as a reference by such models Finally, section 5 will present the results of an integrated experimental and theoretical approach aimed at developing a proper model of the dynamics inherent to a-Si:H and amorphous materials in general Future work necessary to achieve a proper description

of these dynamic processes will be indicated in the Conclusion section

2 Properties of a-Si:H

There exist several preparation methods for a-Si:H films Early work on evaporated and sputtered a-Si:H lead to poor quality films, and it is now widely accepted that Radio Frequency (RF) Glow Discharge produces the best quality material, although other more recent methods claim similar or better results A comprehensive review of the advantages and disadvantages of the different methods employed to grow a-Si:H can be found in the books edited by Searle (1998) and Street (1991)

In general, it is desirable that a hydrogen plasma be employed to help the formation of Si—

Hn ion radicals; hence, methods based on plasma-enhanced chemical vapour deposition (PECVD) techniques are usually preferred The ions produced in the plasma region are directed via an electric field towards a substrate, where film growth takes place A common characteristic of these PECVD techniques is the possibility of tuning the system using several parameters, which might be mutually dependent on or independent of each other, like partial gas pressure, electrode bias, substrate bias, flow rates, gas mixtures, substrate temperature, and any other adjustable parameter A review of plasma deposition of a-Si:H

can also be found in (Bruno et al.,1995)

If the goal of current research in this sector is the understanding and prediction of the properties of a-S:H, it is crucial that the dependence of physical properties on preparation conditions be fully examined This requires the development of experimental and predictive tools applicable to size scales ranging from the atomic to the macroscopic levels Both Searle (1998) and Street (1991) provide an exhaustive review of the structural, optical and electronic properties of a-Si:H, and point out the still unresolved issues In the following subsection, the basic properties of a-Si:H are presented, with a focus on the role of hydrogen

Optoelectronic Properties of Amorphous Silicon

2.1 Structure and Density of States (DOS)

In order to understand the implication of the amorphous structure of a-Si:H on its electronic properties, it is useful to examine the structure of amorphous silicon in comparison to its crystalline form (c-Si) Crystalline silicon is characterized by the well known diamond (or tetrahedral) structure, with bond length of 23.3 nm and bond angle of 109.5o As a matter of fact, the amorphous form shows very small changes from the crystalline parameters, with a ± 10% deviation in bond length, and a ± 5% deviation in bond angle These small changes make it possible to maintain a relatively good short range order (within the first 2-3 nearest neighbours); however, the accumulation of structural stress, due to the progressive compounding of small deviations, eventually leads to bond breaking and the appearance of dangling bonds Figure 1 shows simple 2-d schematics of the formation of dangling bonds: a 2-d square crystal (1a) is slightly distorted (1b, top, center atom) The distortions become more marked as the network is extended, and eventually a dangling bond (DB) appears to relieve the structural stress (top right quadrant of figure 1c: this is usually also accompanied by under-coordinated and over-coordinated bonds)

opto-Fig 1 (a to c) 2-d schematics of formation of dangling bonds due to long range disorder The negative effects of the dangling bonds on the opto-electronic properties of a-Si can be effectively removed by hydrogenation; that is, hydrogen atoms are introduced to passivate (bond to) the dangling bonds; see, for instance, (Kasap, 2005; Street 1991, 2000)

Hydrogen atoms incorporated into the films satisfy the covalent bonds at defects and microvoids and also allow the lattice to relax, thereby reducing the density of localized states by several orders of magnitude Figure 2(b) show a 3-d representation of amorphous silicon with dangling bonds passivated by hydrogen atoms A crystalline structure is also shown for comparison in figure 2(a)

The differences and similarities between the crystalline silicon and amorphous silicon structures are evident when we examine the radial distribution functions (RDF) for the two structures, as shown in Figure 3 The amorphous structure still shows ordered, crystalline features for the first 3 nearest neighbors The first neighbor also maintains the crystalline sharpness for the peak, while the progressive deviations from the crystalline structure are evident in the spreading of the peaks for the second and third nearest neighbor