WWW.DISSERTATION.XLIBX.INFO
FREE ELECTRONIC LIBRARY - Dissertations, online materials
 
<< HOME
CONTACTS



Pages:   || 2 | 3 | 4 | 5 |   ...   | 12 |

«PHOTO-DYNAMIC XPS FOR INVESTIGATING PHOTOINDUCED VOLTAGE CHANGES IN SEMICONDUCTING MATERIALS A DISSERTATION SUBMITTED TO THE DEPARTMENT OF CHEMISTRY ...»

-- [ Page 1 ] --

PHOTO-DYNAMIC XPS FOR INVESTIGATING PHOTOINDUCED

VOLTAGE CHANGES IN SEMICONDUCTING MATERIALS

A DISSERTATION SUBMITTED TO

THE DEPARTMENT OF CHEMISTRY

AND THE GRADUATE SCHOOL OF ENGINEERING AND SCIENCE

OF BILKENT UNIVERSITY

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

By

HİKMET SEZEN

December, 2011 I I certify that I have read this thesis and that in my opinion is it is fully adequate, in scope and in quality, as a dissertation for the degree of the doctor of philosophy, …………………………………………..

Prof. Dr. Şefik Süzer (Principal Advisor) I certify that I have read this thesis and that in my opinion is it is fully adequate, in scope and in quality, as a dissertation for the degree of the doctor of philosophy, …………………………………………..

Prof. Dr. O. Yavuz Ataman I certify that I have read this thesis and that in my opinion is it is fully adequate, in scope and in quality, as a dissertation for the degree of the doctor of philosophy, …………………………………………..

Prof. Dr. Ekmel Özbay II I certify that I have read this thesis and that in my opinion is it is fully adequate, in scope and in quality, as a dissertation for the degree of the doctor of philosophy, …………………………………………..

Assoc. Prof. Dr. Oğuz Gülseren I certify that I have read this thesis and that in my opinion is it is fully adequate, in scope and in quality, as a dissertation for the degree of the doctor of philosophy, …………………………………………..

Assist. Prof. Dr. Emrah Özensoy

Approved for the Graduate School of Engineering and Science:

…………………………………………..

Prof. Dr. Levent Onural (Director of the Institute) III ABSTRACT

PHOTO-DYNAMIC XPS FOR INVESTIGATING PHOTOINDUCED

VOLTAGE CHANGES IN SEMICONDUCTING MATERIALS

HİKMET SEZEN

Ph.D. in Chemistry Supervisor: Prof. Dr. Şefik Süzer December, 2011 The main motivation of this Ph.D. study is investigation of the photoinduced voltage changes in semiconductive materials with X-ray Photoelectron Spectroscopy (XPS). For this purpose, we have developed a technique for recording the shifts in the positions of the XPS peaks in response to different waveforms of electrical and/or optical stimuli for tracing dynamics of the developed potentials originating from intrinsic or extrinsic factors of the semiconductive materials such as charging/discharging, photoconductivity, surface photovoltage, band-bending/flattening/inversion, etc.

Within this purpose, the surface photovoltage behaviors of n- and p-type doped Si and GaN samples are examined with the photo-dynamic XPS, to follow the behavior of the bandbending under photoillumination in both static and dynamic fashions. The band inversion effects are clearly observed on the n- and p-Si samples in the presence of a dielectric silica overlayer and on the p-GaN sample due to variation of the illuminating laser energies.

–  –  –

assessed after correction of their surface photovoltage values.

A laser patterned silicon wafer with a high-power near infrared fiber laser is also investigated. While the patterned silica domains have identical chemical composition with the non-patterned regions, an investigation with dynamic XPS clearly reveals distinct dielectric characteristics of the patterned domains.

Electrical parameters of CdS thin film are extracted by dynamic XPS with and without photoillumination. The photo-dynamic XPS technique has also provided useful information by disentanglement of processes; charging/discharging, photoconductivity, and surface photovoltage. Furthermore, location (space) dependent resistance and chemical profile of a CdS based Light Dependent Resistor (LDR) is also probed during realistic operational conditions, by utilizing spatially resolved XPS analysis (in the area mapping mode). In addition, with the XPS mapping analysis defects and malfunctioning sites/domains have been located under various experimental and preparation conditions.

Keywords: XPS, Dynamic XPS, Photo-Dynamic XPS, Charging, Discharging, Charge Contrast, Photoconductivity, Surface Photovoltage, Band-Bending, Band-Flattening, and Band-Inversion, Laser Patterning, Light Dependent Photoresistor.

–  –  –

Bu doktora tezinin temel amacı, ışık uyarılmaları altında, yarıiletken malzemeler üzerinde meydana gelen voltaj yüklenmelerinin X-ışını fotoelektron spektroskopisi (XPS) ile incelenmesidir. Öncelikle malzemeleri değişik şekil ve hızlarda hem elektriksel hem de ışıksal olarak uyarabileceğimiz, aynı zamanda yarıiletken malzemelerin içsel ve dışsal özelliklerine bağlı olarak meydana gelebilecek potansiyel değişimlerini takip edebileceğimiz yeni bir teknik olan foto-dinamik XPS tekniğini geliştirdik.





Bu amaç dogrultusunda, hem n- ve p-Si hem de n- ve p-GaN numunelerinin yüzey fotovoltaj davranışları, yüzey bant düzlenmeleri statik ve dinamik ışık uyarımları yardımı ile XPS kullanılarak takip edildi. Ayrıca, yarıiletkenler üzerinde bant ters-eğrilme etkileri n- ve pSi için ince bir silika tabakası oluşturulduğu zaman, ayrıca p-GaN için farklı dalga boylarında bulunan ışıklar ile uyarıldığı süreçlerde gözlemlendi. Ek olarak, bu teknik ile silikon numunelerindeki eser miktarda eklenmiş bulunan elementler vasıtasıyla ortaya çıkan enerji

–  –  –

kullanarak takip edilebileceğini gösterdik.

Yüksek yoğunluktaki kızılötesi lif lazer ile silikon üzerindeki desenlendirilmiş bölgeler XPS yardımı ile incelendi. Kimyasal içerik olarak, lazere maruz tutulan ve tutulmayan bölgeler arasında herhangi bir fark yok iken, dinamik XPS ile yaptığımız deneyler sayesinde lazer ile desenlendirilmiş bölgelerin kendine özgü dieletriksel özelliği olduğu gösterildi.

CdS filminin elektriksel özellikleri, ışık varlığında ve yokluğunda dinamik XPS kullanılarak ölçüldü. Ayrıca, foto-dinamik XPS tekniğinden, yüklenme, yük boşalması, fotoiletkenlik ve yüzey fotovoltaj gibi etkileri birbirlerinden ayırmada etkin bir şekilde yararlanılabileceği gösterildi. Ek olarak, CdS içeren bir fotoselin konuma bağımlı direnç ve kimyasal analizleri alan haritalamalı XPS ile ölçülmüştür. İlaveten, alan haritalamalı XPS kusurlu veya hatalı bölgelerin farklı koşullar altında ortaya çıkması ve bu farklı bölgeler arasında karşılaştırmalar yapabilmemizi sağladı.

Anahtar Kelimeler: XPS, Dinamik XPS, Foto-Dinamik XPS, Yüklenme, Yük Boşalması, Yük Ayrışımı, Fotoiletkenlik, Yüzey Fotovoltaj, Bant Eğrilmesi, Bant Düzelmesi, Bant TersEğrilmesi, Lazer, Laser Desenlendirme, Işığa Bağımlı Direnç (Fotosel).

–  –  –

XPS: X-Ray Photoelectron Spectroscopy UHV: Ultra High Vacuum BE: Binding Energy KE: Kinetic Energy eV: Electron-Volt hυ: Kinetic Energy of Photon Ф: Work Function FWHM: Full With Half Maximum AL: Attenuation Length IMFP: Inelastic Mean Free Path I: Electric Current or Intensity of Light Ix-ray: X-rays Induced Current Ifil: Flood Gun Induced Current DC: Direct Current SQW: Squarewave ZPC: Zero Point Charge B.E. Diff.: Binding Energy Difference V: Electric Potential R: Resistance or Resistor Rph: Photoresistance or Photoresistor C: Capacitance or Capacitor RC: Parallel Connected Resistor and Capacitor unit FG: Flood Gun or Function Generator VCCS: Voltage Controlled Current Source σ: Conductivity SPV: Surface Photovoltage a.u.: Arbitrary Unit KP: Kelvin Probe NIR: Near Infrared CW: Continuous Wave VIII Ei: Intrinsic Fermi level Ef: Fermi level VB: Valance Band CB: Conduction Band NDF: Neutral Density Filter OD: Optical Density LDR: Light Dependent Resistor Rsb: Electron Excitation from Surface to Bulk Rbs: Electron Excitation from Bulk to Surface TC: Time Constant

–  –  –

degree, but is an enjoyable period of my life, and an impressive preface of my academic carrier. The most probable reason is the great interaction with my supervisor, Prof. Dr. Şefik Süzer, for the whole duration. I am aware of the privilege of working with my supervisor, and so I express my deepest thankfulness to him.

I would also like to convey my deepest thanks to Dr. Gülay Ertaş, who also supervised me during each step of my work. I thank to Prof. Dr. Mehmet Erbudak, Prof. Dr. Ekmel Özbay, Prof. Dr. Atilla Aydınlı, Assist. Prof. Dr. Ömer İlday, Assist. Prof. Dr. Özgür Aktaş, Assist. Prof. Dr. Özgür Birer, and Assoc. Prof. Dr. Oğuz Gülseren, who have significant roles in completion of my thesis. In addition, I also thank to Dr. Tim Nunney, Dr. Kevin S Robinson, and members of Surface Analysis Department of the ThermoFisher Co., UK, for their patience and kindness to our endless requests about the K-Alpha instrument.

Thanks also to current and previous Süzer-lab members; Merve Taner, Eda Yılmaz (Özkaraoğlu), Pınar Cönger, İlknur Kaya Tunç, Hacı Osman Güvenç, Sinem Yılmaz, Sevnur Kömürlü, Korcan Demirok, Bora İnci, Ferdi Karadaş, and Engin Karabudak.

I would like to express my appreciations to my dear friends for moral support without any remuneration; Cemal Albayrak, Mustafa Fatih Genişel, Yurdanur Türker, Emre Emmez and Emrah Parmak. Also special thanks to Ethem Anber, Emine Yiğit, Hüsnü İçer, and Bülent Öktem.

I always feel myself indebted to Bilkent University and Chemistry Department for providing a high level education and research opportunity.

Finally, I want to express my deepest gratitude to my family and my love Feriza Sezen if I could.

X

Table of Contents

ABSTRACT……………………………………………………………………………….... IV ÖZET………………………………………………………………………………………... VI LIST OF ABBREVATIONS……………………………………………………………... VIII ACKNOWLEDGEMENTS………………………………………………………………… X Table of Contents…………………………………………………………………………… XI LIST OF FIGURES………………………………………………………………………. XIII LIST OF TABLE….……………………………………………………………….……. XVIII

1. Introduction

1.1. X-Ray Photoelectron Spectroscopy

1.1.1. Controlled Surface Charging

1.2. Photoconductivity

1.3. Surface Photovoltage

2. Aim of Work

3. Experimental

3.1. Sample Preparation

3.2. Instruments and Technique

3.2.1. Method and Model of Photo-Dynamic XPS

4. Results and Discussion

4.1. Surface Photovoltage and Band Offset Measurements on n- and p-type Si.................. 37 4.1.1. Inversion of the Surface Photovoltage of SiOx / n- and p-doped Si

4.1.2. Dynamical Photoconductivity and Surface Photovoltage Response of a SiO x / ptype Si Surface Structure

4.1.3. Elemental, Chemical, and Electrical Investigation of a High-Power Fiber Laser Patterned Silicon

–  –  –

4.2.1. An XPS Investigation of CdS Based Photoresistor under Realistic Operational Conditions

4.3. Surface Photoresponse and Transients of n- and p-type GaN

4.3.1. Inversion of the Surface Photovoltage of p-type GaN

5. Conclusions

6. References

XII

LIST OF FIGURES

Figure 1. Basic principles and components of XPS experimental setup.

Figure 2. Schematic representation of the photoelectric effect.

Figure 3. (a) Photoelectric effect due to x-ray radiation and elastic and inelastic collision of photoelectron (b) Beer-Lambert’s relation and depth profile of XPS with calculated values of corresponding intensity distribution from first three attenuation lengths.

. 6 Figure 4. Charging processes in (a) a conductive and (b) a nonconductive material during recording of XPS data.

Figure 5. (a) XPS spectra of the Si2p region of a SiO2/p-Si sample connected to ground (green) and to +10 V(red) and – 10 V (blue) external DC stresses.

The thickness of the silica overlayer is ca. 4 nm. (b) The variation of the current passing through the sample under various bias potentials. The inset on the top right depicts the experimental setup.

Figure 6. XPS spectra of the Au4f region, when the metal is connected externally to; (a) ground; (b) SQW excitation of ±10.

00 amplitude and at frequencies of 10 kHz (navy spectrum) and 0.001 Hz (magenta spectrum). The same spectra are reproduced after connecting to an external circuit, consisting of; (c) a series resistor (R=220 kΩ); (d) a series resistor and a parallel capacitor (R=220 kΩ, C=500 nF). A schematic diagram of the experimental set-up is given as an inset, where IX-ray represents the electron current due to photo and secondary electrons generated, and IFlood is the current due to the flood-gun used.

Figure 7. Photoinduced electron-hole generation and separation in between n- and p-type semiconductor.

Figure 8. The band diagram of n-Si (a) in dark (b) under photoillumination and (c) in flattened conditions.

Adapted from the references 57, 58, 59, and 60.

Figure 9. The representative Si lattice structures of the n- and p-type doped with (a) P (b) B elements.

Adapted from the references 55 and 56.

Figure 10. (a) The XPS spectra and (b) band diagram of n- and p-type doped Si without and with exciting light source (violet laser).



Pages:   || 2 | 3 | 4 | 5 |   ...   | 12 |


Similar works:

«Learning Distance Functions for Exemplar-Based Object Recognition by Andrea Lynn Frome B.S. (Mary Washington College) 1996 A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Computer Science in the GRADUATE DIVISION of the UNIVERSITY OF CALIFORNIA, BERKELEY Committee in charge: Professor Jitendra Malik, Chair Professor Michael I. Jordan Professor Bruno Olshausen Fall 2007 The dissertation of Andrea Lynn Frome is approved: Professor...»

«Physics College of Science Graduate Programs 2014-1015 Contents Faculty 1 The Graduate Programs 5 The Doctor of Philosophy Degree 6 The Master of Science Degree 15 Our Mission: To educate students for a life of fulfillment and accomplishment. To Create and translate knowledge to meet global and societal needs. Northeastern University is an equal opportunity/affirmative action Title IX education institution and employer. Tuition rates, all fees, rules and regulations, courses, and course content...»

«The Dark Side of European Integration: Nationalism and Radical Right Mobilization in Contemporary Europe By Alina Naumovna Polyakova A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Sociology in the Graduate Division of the University of California, Berkeley Committee in charge: Neil Fligstein, Chair Dylan Riley Jason Wittenberg Fall 2013 The Dark Side of European Integration: Nationalism and Radical Right Mobilization in...»

«ABSTRACT Title of Document: THE EFFECTS OF BUILDING INFORMATION MODELING ON CONSTRUCTION SITE PRODUCTIVITY Douglas E. Chelson, Doctor of Philosophy, 2010 Directed By: Professor Miroslaw J. Skibniewski, Ph.D., A. James Clark Chair Civil & Environmental Engineering Construction experiences low productivity compared to other industries, largely attributed to poor planning and communication. Building Information Modeling (BIM) is a process that is used to resolve these problems by simulating...»

«The Temple, the Spirit and the People of the Presence of God: Examining Critical Options for a Pentecostal Ecclesiology by Robert Brian Robson A thesis submitted to Wycliffe College and the Theology Department of the Toronto School of Theology in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Theology awarded by the University of St. Michael’s College © Copyright by Robert Brian Robson 2012 The Temple, the Spirit and the People of God’s Presence:...»

«Byron’s Shakespearean Imitations Benjamin Barber Thesis submitted to the Faculty of Graduate and Postdoctoral Studies in partial fulfillment of the requirements for the Doctorate in Philosophy degree in English Department of English Faculty of Arts University of Ottawa © Benjamin Barber, Ottawa, Canada, 2016 Barber ii Abstract Though Byron is known for his provocative denials of the importance of Shakespeare, his public derogations of the early modern playwright are in fact a pose that hides...»

«c 2014 by Naoki Tanaka. All rights reserved. SUSTAINABLE APPROACHES TO AD-HOC INFORMATION SHARING FOR VIRTUAL ORGANIZATIONS BY NAOKI TANAKA DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computer Science in the Graduate College of the University of Illinois at Urbana-Champaign, 2014 Urbana, Illinois Doctoral Committee: Professor Marianne Winslett, Chair Professor Carl Gunter Professor Nikita Borisov Professor David K. Y. Yau, Purdue...»

«CEBU DOCTORS’ UNIVERSITY Mandaue City, Cebu, Philippines GRADUATE SCHOOL THESIS/DISSERTATION WRITING MANUAL 2015 1 Table of Contents Page I.The Graduate School and its Research Agenda NHERA Research Areas 2 NHURA, RHURA Research Areas 2-3 Institutional Mandate and Philosophy of Graduate Programs 4 Graduate School Vision, Mission, and Goals 4 Research Agenda for Graduate Student Researchers 5 Research Agenda for Faculty Institutional Research 5 II. Types of Research 5 III. Comprehensive...»

«Instructions for use Growth Dynamics and Applications of Selectively–Grown InGaAs Nanowires (有機金属気相選択成長法による InGaAs ナノワイヤの 成長ダイナミクスと素子応用に関する研究) A dissertation submitted in partial fulfillment of the requirement for the degree of Doctor of Philosophy (Engineering) in Hokkaido University February, 2014 by Yoshinori KOHASHI Dissertation Supervisor Professor Junichi MOTOHISA Dedicated to my parents, Etsuko KOHASHI...»

«Ph.D. Ordinances and Regulations (Revised up to 84th Meetings of the Senate) ORDINANCES 0.1 The Indian Institute of Technology Guwahati awards the degree of Doctor of Philosophy (PhD) in Engineering/Design/Sciences/Humanities and Social Sciences (HSS) to a candidate who has successfully completed the stipulated Programme of Research. The Programme of Research with the governing rules and regulations are formulated by the 0.2 Senate of the Institute. The Senate can modify or change the...»

«How can we explain the emergence of a language which benefits the hearer but not the speaker? Marco Mirolli1,2, Domenico Parisi1 1 Institute of Cognitive Sciences and Technologies, National Research Council 15, Viale Marx, 00137 Rome, Italy d.parisi@istc.cnr.it 2 Philosophy and Social Sciences Department, University of Siena 47, Via Roma, 53100 Siena, Italy mirolli2@unisi.it mirolli2@unisi.it 1. Introduction 1.1 The problem Language requires the co-evolution of both speakers and hearers. i.e.,...»

«Fetal Testosterone and Early Autism Spectrum Disorder Related Neurodevelopmental Outcomes Bo Y. Park, MPH A Thesis Submitted to the Faculty of Drexel University by Bo Y. Park in partial fulfillment of the requirements for the degree of Doctor of Philosophy June 2015 ©Copyright 2015 Bo Y. Park. All Rights Reserved. Dedication For Eleanor and Evelyn. Tough moments are the beautiful ones. Acknowledgements I am very fortunate to have had the opportunity to learn and grow surrounded by great...»





 
<<  HOME   |    CONTACTS
2016 www.dissertation.xlibx.info - Dissertations, online materials

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.