DOCSLIB.ORG

Characterization of Cadmium Zinc Telluride Solar Cells by RF Sputtering Senthilnathan Subramanian University of South Florida

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Characterization of Cadmium Zinc Telluride Solar Cells by RF Sputtering Senthilnathan Subramanian University of South Florida University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School 6-24-2004 Characterization of Cadmium Zinc Telluride Solar Cells by RF Sputtering Senthilnathan Subramanian University of South Florida Follow this and additional works at: https://scholarcommons.usf.edu/etd Part of the American Studies Commons Scholar Commons Citation Subramanian, Senthilnathan, "Characterization of Cadmium Zinc Telluride Solar Cells by RF Sputtering" (2004). Graduate Theses and Dissertations. https://scholarcommons.usf.edu/etd/1261 This Thesis is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. Characterization of Cadmium Zinc Telluride Solar Cells by RF Sputtering by Senthilnathan Subramanian A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering Department of Electrical Engineering College of Engineering University of South Florida Major Professor: Christos S. Ferekides, Ph.D. Don L. Morel, Ph.D. Yun L. Choiu, Ph.D Date of Approval: June 29, 2004 Keywords: czt, thin films, wide bandgap semiconductors, tandem solar cells © Copyright 2004 , Senthilnathan Subramanian DEDICATION This thesis is dedicated to my family and friends for their love and support. ACKNOWLEDGEMENT I would like to express my gratitude to my Major Professor Dr. Chris Ferekides for his invaluable guidance and support during the course of this work. He has been a great source of inspiration during my work here. I also thank Dr.Don L. Morel and Dr. Yun L. Choiu for their guidance in the fulfillment of this thesis and graduate program. A special thank to all my colleagues, roommates and friends for their constant support and encouragement during this work. TABLE OF CONTENTS LIST OF TABLES iv LIST OF FIGURES v LIST OF SYMBOLS vii ABSTRACT viii CHAPTER 1 INTRODUCTION 1 1.1 Introduction 1 1.2 Renewable Energy 1 1.3 Photovoltaic Effect 2 1.4 Tandem Solar Cell 4 CHAPTER 2 INTRODUCTION TO SOLAR CELLS 7 2.1 PN Junctions 7 2.2 Heterojunctions 7 2.3 Solar Cells 11 2.4 Parameters of a Solar Cell 11 2.5 Current Flow in a Solar Cell 14 CHAPTER 3 LITERATURE REVIEW 19 CHAPTER 4 PROCESSING 32 4.1 Device Structure 32 4.2 Transparent Conducting Oxides 33 i 4.3 Window Layer 33 4.4 Absorber Layer (Cd1-xZnxTe) 34 4.5 Zinc Telluride Deposition 36 4.6 Zinc Chloride Treatment 37 4.6.1 Air Annealing 37 4.6.2 Vapor Treatment in the Oven 37 4.6.3 Oxygen Free Sublimation 38 4.7 Back Contact 39 4.8 Measurements 40 4.8.1 I-V Measurements 40 4.8.2 Spectral Response 40 4.8.3 XRD, SEM and AFM 40 CHAPTER 5 RESULTS AND DISCUSSION 41 5.1 Properties of CZT Films 41 5.2 CZT in Argon Ambient 45 5.2.1 Effects of Contact Annealing on Cell Characteristics 45 5.2.2 Heat Treatment on CZT Devices 46 5.3 CZT Films Deposited in Ar/N2 Ambient 47 5.3.1 Effect of CdS Thickness on CZT Devices 49 5.4 CZT on Transparent Conducting Oxides 51 5.5 Transparent Back Contact on CZT Films 53 5.6 CZT Graded Devices 54 5.7 Post Deposition Treatments of CZT 57 5.8 Zinc Chloride Treatment on CZT Films 57 5.8.1 ZnCl2 Treatment on CSS-CZT Substrates 61 CHAPTER 6 CONCLUSION 64 REFERENCES 66 ii APPENDICES 69 APPENDIX A 70 APPENDIX B 71 iii LIST OF TABLES Table 1. Composition and Bandgap of Cd1-xZnxTe Films 20 Table 2. Condition and Results of Post Deposition Heat Treatment of Cd1-xZnxTe/CdS/ITO/7059 Film in Various Ambient 22 Table 3. Devices Results for Cd1-xZnxTe/CdS/ITO/7059 23 Table 4. Comparison of CdZnTe Cells Annealed in Different Ambient 25 Table 5. Substrate Temperature Calibrations 36 Table 6. Voc of Devices at Different Annealing Temperatures 47 Table 7. Voc and Jsc of Copper Back Contacted Samples 53 Table 8. Voc of Copper Back Contacted Samples at Various Conditions 54 Table 9. Voc and Jsc of Type A Graded Samples 56 Table 10. CSS ZnCl2 Treated Oxygen Free Sublimation CZT Sample 63 Table 11. History Sheets of XRD Samples 70 Table 12. XRD Peaks for Figure 30 71 Table 13. XRD Peaks for Figure 40 72 Table 14. XRD Peaks for Figure 42 73 iv LIST OF FIGURES Figure 1. Solar Cell, Module and Solar Array 3 Figure 2. Efficiencies of PV Cells and Modules 4 Figure 3. Iso-efficieny Curves for a Two-Cell Tandem Device Versus the Energy Bandgap of the Cell 5 Figure 4. Three Layer Tandem Structure Used in Space Applications 6 Figure 5. Band Diagram of a p-N Anisotype Heterojunction Before and After Contact 9 Figure 6. Types of Heterojunctions (a) nN Isotype Heterojunctions, (b) pP Isotype Heterojunctions, (c) Np Anisotype Heterojunction, (d) nP Anisotype Heterojunction 10 Figure 7. Gradual Smoothing of the Interface Spike of an n-P Heterojunction by Compositional Grading 11 Figure 8. Equivalent Circuit of a Solar Cell 12 Figure 9. Dark-Light I-V Characteristics of a Solar Cell 13 Figure 10. Energy Band Structure of P-N Junction 15 Figure 11. Light Interaction and Current Flow in a Photovoltaic Cell 17 Figure 12. II – VI Bandgaps 19 Figure 13.Variation in Bandgap and Lattice Parameter with x for Cd1-xZnxTe Films 21 Figure 14. X-ray Diffraction of MBE Grown CdZnTe Films 23 Figure 15. Forward Bias Dark I-V Characteristics of (a) CdTe, (b)CZT (1.7eV) and (c) CZT (1.8eV) Cell Structures 24 Figure 16. Transmission of CdZnTe Films Annealed in (a) No Anneal (b) Argon Anneal, (c) Forming Gas Anneal, (d) Air Anneal 26 Figure 17. Auger Depth Profile of CdZnTe Film Over ITO/Glass Substrate 27 Figure 18. Auger Depth Profile of CdZnTe Films Grown on CdS/ITO/Glass 27 Figure 19. Cross-section of Sample Used for Interdiffusion Studies 28 Figure 20. AES for As-deposited HT Samples 29 Figure 21. AES Data for CdCl2 Annealed HT Samples 30 v Figure 22. AES Data of As-deposited LT Samples 30 Figure 23. AES Data of CdCl2 Annealed LT Samples 31 Figure 24. Structure of CZT Device 32 Figure 25. CZT Sputtering Unit 35 Figure 26. Vapor Treatment in an Oven 38 Figure 27. Chamber for Oxygen Free ZnCl2 Process 39 o Figure 28. Transmission Response of CZT Film Deposited in Ar with TSUB ~ 350 C 42 o Figure 29. Bandgap of CZT Film Deposited in Ar with TSUB ~ 350 C 42 Figure 30. XRD of CZT Film on CdS/SnO2 Substrate 43 Figure 31. AFM Image of CZT Film on CdS Substrate 44 Figure 32. SEM of CZT Films Deposited at 300oC 44 Figure 33. SEM of CZT Films Deposited at 400oC 45 Figure 34. Light I-V Characteristics of As-deposited and Contact Annealed Devices 46 Figure 35. Dark and Light I-V Characteristics of CZT in Ar/N2 and Annealed in He at 500oC for 5 Mins 48 Figure 36. Spectral Response of CZT in Ar/N2 and Annealed in He at 500oC for 5 Mins 49 Figure 37. Effect of CdS Thickness on CZT 50 Figure 38. Spectral Response of CZT with Different CdS Thicknesses 51 Figure 39. XRD of SnO2/CZT at Different Annealing Temperatures 52 Figure 40. Spectral Response of CZT on SnO2 Substrate 53 Figure 41. XRD of Graded Samples 55 Figure 42. Spectral Response of Graded Samples 56 Figure 43. Voc and Jsc of ZnCl2 Air Annealed Samples at Different Temperatures 58 Figure 44. Effects of ZnCl2 Air Annealing Treatment 59 Figure 45. Effect of ZnCl2 Annealing Temperatures 60 Figure 46. Spectral Response of CZT Device by Vapor Treatment 60 Figure 47. ZnCl2 Thermal Annealed CSS CZT Devices 61 Figure 48. Spectral Response of Vapor Annealed CSS CZT Devices 62 Figure 49. Spectral Response of Post Deposition Hydrogen Annealed and ZnCl2 Treated Devices 63 vi LIST OF SYMBOLS a Lattice Constant (Å) Ec Energy Of Conduction Band Edge (eV) EF Fermi Level Energy (eV) Ev Energy Of Valence Band Edge (eV) FF Fill Factor h Planck Constant (J-s) h ν Photon Energy (eV) I Current (A) Isc Short Circuit Current (A) 2 Jsc Short Circuit Current Density (A/cm ) k Boltzmann Constant (eV/k) q Electron Charge (1.6 x 10 -19 C) 2 Rs Series Resistance (Ω/cm ) 2 Rsh Shunt Resistance (Ω/cm ) Voc Open Circuit Voltage (V) α Optical Absorption Coefficient (cm-1 ) ∆E Energy Difference (eV) ∆ Ec, ∆ Ev Conduction and Valence Band Discontinuities (eV) λ Wavelength (nm) ν Frequency Of Light (sec-1) ρ Bulk Resistivity (Ω cm) φ Work Function (eV) χ Electron Affinity (eV) vii CHARACTERIZATION OF CADMIUM ZINC TELLURIDE SOLAR CELLS BY RF SPUTTERING Senthilnathan Subramanian ABSTRACT High efficiency solar cells can be attained by the development of two junctions one stacked on top of each other into tandem structures. So that, if a photon is not able to excite an electron-hole pair in the top cell can create a pair in the bottom cell, which has a smaller bandgap. For a two junction tandem device structure, the bandgap of the top cell should be 1.6-1.8eV and for the bottom cell should be 1eV to attain efficiencies in the range of 25%. Cadmium Zinc Telluride which has a tunable bandgap of 1.45- 2.2eV is a candidate for the top cell of the tandem structure. Cadmium Zinc Telluride (Cd1-xZnxTe) films were deposited by co-sputtering of CdTe and ZnTe.
Load more

Recommended publications
  • Progress in the Development of Cdte and Cdznte Semiconductor Radiation Detectors for Astrophysical and Medical Applications
    Sensors 2009, 9, 3491-3526; doi:10.3390/s90503491 OPEN ACCESS sensors ISSN 1424-8220 www.mdpi.com/journal/sensors Review Progress in the Development of CdTe and CdZnTe Semiconductor Radiation Detectors for Astrophysical and Medical Applications Stefano Del Sordo 1,*, Leonardo Abbene 1,2,*, Ezio Caroli 3, Anna Maria Mancini 4, Andrea Zappettini 5 and Pietro Ubertini 6 1 INAF/IASF Palermo, Via Ugo La Malfa 153, 90146 Palermo, Italy 2 Dipartimento di Fisica e Tecnologie Relative, Università di Palermo,Viale delle Scienze, 90128 Palermo, Italy 3 INAF/IASF Bologna, Via Gobetti 101, 40129 Bologna, Italy; E-Mail: [email protected] (E.C.) 4 Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Via Arnesano, 73100 Lecce, Italy; E-Mail: [email protected] (A.M.M.) 5 IMEM-CNR, Parco Area delle Scienze 37/A, 43100 Parma, Italy; E-Mail: [email protected] (A.Z.) 6 INAF/IASF Roma, Via del Fosso del Cavaliere 100, 00133 Roma, Italy; E-Mail: [email protected] (P.U.) * Authors to whom correspondence should be addressed; E-Mails: [email protected]; (S.D.S.); [email protected] (L.A.); Tel. +39-091-6809563; Fax: +39-091-6882258 (S.D.S.); Tel. +39-091-6615053; Fax: +39-091-6615063 (L.A.) Received: 26 March 2009; in revised form: 5 May 2009 / Accepted: 8 May 2009 / Published: 12 May 2009 Abstract: Over the last decade, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors.
    [Show full text]
  • Two Cadmium Zinc Telluride (CZT) Semiconductor Detectors, a Lacl3(Ce) Scintillator, and an Nai(Tl) Scintillator
    Performance comparison of four compact room- temperature detectors – two cadmium zinc telluride (CZT) semiconductor detectors, a LaCl3(Ce) scintillator, and an NaI(Tl) scintillator John K. Hartwell, Member IEEE, Robert J. Gehrke, and Michael E. Mc Ilwain measurement scenarios where portability, compact design, Abstract— The performance characteristics of four compact, and freedom from cryogenics are primary considerations. room-temperature detectors – two scintillators and two A recent publication provided performance comparison semiconductor detectors – were studied. All are commercially- data on three detectors including a ∅10 cm X 10 cm NaI(Tl), available detectors. The two scintillators were a ∅13 mm X a ∅55 mm X 54 mm HPGe detector, and a ∅9 mm X 2 mm 13 mm lanthanum chloride [LaCl3(Ce)] detector and a ∅25 mm X 25 mm sodium iodide [NaI(Tl)] detector. The two CdTe detector [1]. Our work, reported in this paper, provides semiconductor detectors were a 10 mm X 10 mm X 3 mm complimentary assessment data on a different suite of four cadmium zinc telluride (CZT) detector with a coplanar gridded highly portable detectors, including work with the promising anode and a 5 mm X 5 mm X 5 mm CZT detector with an new scintillator LaCl3(Ce). extended cathode. The efficiency, resolution, and peak shape of these devices are compared. Since LaCl (Ce) is a relatively new 3 II. EXPERIMENTAL METHOD commercial scintillator material, additional information on the performance of this detector is presented. Specifically, the The electronics system used for these evaluations consisted impact of naturally-occurring radioactive 138La and additional of a preamplifier, a linear amplifier (Tennelec TC244 or Ortec contamination from alpha-emitting radionuclides on the 460), and an multichannel analyzer (Amptek MCA8000A) background measured with this detector are discussed.
    [Show full text]
  • Research Progress on Ultra-Precision Machining Technologies for Soft-Brittle Crystal Materials
    Front. Mech. Eng. 2017, 12(1): 77–88 DOI 10.1007/s11465-017-0411-8 REVIEW ARTICLE Hang GAO, Xu WANG, Dongming GUO, Yuchuan CHEN Research progress on ultra-precision machining technologies for soft-brittle crystal materials © The Author(s) 2017. This article is published with open access at link.springer.com and journal.hep.com.cn 2017 Abstract Soft-brittle crystal materials are widely used in Mercury cadmium telluride (HgCdTe, MCT) single crystal many fields, especially optics and microelectronics. is the most significant material for infrared optoelectronic However, these materials are difficult to machine through devices and MCT-based high performance infrared traditional machining methods because of their brittle, soft, devices, and is widely used in the fields of aeronautics and anisotropic nature. In this article, the characteristics and astronautics [4]. Cadmium zinc telluride (CdZnTe, and machining difficulties of soft-brittle and crystals are CZT) single crystal is the most promising material for the presented. Moreover, the latest research progress of novel fabrication of room temperature radiation detectors [5,6] machining technologies and their applications for soft- and is also widely used as the perfect substrates for brittle crystals are introduced by using some representative growing epitaxial layers of MCT crystal [7]. CaF2 single materials (e.g., potassium dihydrogen phosphate (KDP), crystal is extensively applied in deep ultraviolet photo- cadmium zinc telluride (CZT)) as examples. This article lithography, solid-state lasers, and high-energy radiation reviews the research progress of soft-brittle crystals detection [8]. BaF2 single crystal with high transparency processing. for infrared and visible light is often used in CO2 laser hatch and infrared optical systems [9].
    [Show full text]
  • Fabrication of Small-Pixel Cdznte Sensors and Characterization with X-Rays
    sensors Article Fabrication of Small-Pixel CdZnTe Sensors and Characterization with X-rays Stergios Tsigaridas 1,∗,† , Silvia Zanettini 2 , Manuele Bettelli 3 , Nicola Sarzi Amadè 3 , Davide Calestani 3 , Cyril Ponchut 1 and Andrea Zappettini 3 1 European Synchrotron Radiation Facility (ESRF), 71 Avenue des Martyrs, F-38043 Grenoble, France; [email protected] 2 Due2lab s.r.l., via Paolo Borsellino 2, 42019 Scandiano, Italy; [email protected] 3 IMEM-CNR, Istituto Materiali per l’Elettronica e il Magnetismo, Consiglio Nazionale delle Ricerche, Parco Area delle Scienze 37/A, 43124 Parma, Italy; [email protected] (M.B.); [email protected] (N.S.A.); [email protected] (D.C.); [email protected] (A.Z.) * Correspondence: [email protected] † Current address: TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada. Abstract: Over the past few years, sensors made from high-Z compound semiconductors have attracted quite some attention for use in applications which require the direct detection of X-rays in the energy range 30–100 keV. One of the candidate materials with promising properties is cadmium zinc telluride (CdZnTe). In the context of this article, we have developed pixelated sensors from CdZnTe crystals grown by Boron oxide encapsulated vertical Bridgman technique. We demonstrate the successful fabrication of CdZnTe pixel sensors with a fine pitch of 55 µm and thickness of 1 mm and 2 mm. The sensors were bonded on Timepix readout chips to evaluate their response to X-rays Citation: Tsigaridas, S.; Zanettini, S.; provided by conventional sources. Despite the issues related to single-chip fabrication procedure, Bettelli, M.; Sarzi Amadè, N.; reasonable uniformity was achieved along with low leakage current values at room temperature.
    [Show full text]
  • Cd,-,Zn,Te Materials
    Source of Acquisition NASA Goddard Space Flight Center Temperature Evolution of Excitonic Absorptions in Cd,-,Zn,Te Materials Manuel A. Quijada and Ross Henry Goddard Space Flight Center, Code 551, Greenbelt, MD 20771, USA ABSTRACT The studies consist of measuring the frequency dependent transmittance (T) and reflectance (R) above and below the optical band-gap in the W/Visible and infrared frequency ranges for Cdl-,Zn,Te materials for x=O and XI-0.04. Measurements were also done in the temperature range from 5 to 300 K. The results show that the optical gap near 1.49 eV at 300 K increases to 1.62 eV at 5 K. Finally, we observe sharp absorption peaks near this gap energy at low temperatures. The close proximity of these peaks to the optical transition threshold suggests that they originate from the creation of bound electron-hole pairs or excitons. The decay of these excitonic absorptions may contribute to a photoluminescence and transient background response of these back-illuminated HgCdTe CCD detectors. Keywords: Keywords: CdZnTe, UV/Vis infrared, transmittance, reflectance, semiconducting gap, photolumi- nescence, exciton 1. INTRODUCTION The ternary compound Cdl-,Zn,Te (CdZnTe) is a semiconducting alloy that is widely used as a base material for x-ray and infrared detectors. In particular, single crystals of CdZnTe wafers are the principal material on which HgCdTe epitaxial layers have been recently grown for the fabrication of infrared sensors on lattice matched CdZnTe substrate.l This has been possible due to recent advances through use of new detector growth technologies2 which involve p/n double layer planar heterostructure arrays grown by Molecular Beam Epitaxy (MBE).
    [Show full text]
  • Photoluminescence Study of Cadmium Zinc Telluride
    Graduate Theses, Dissertations, and Problem Reports 2001 Photoluminescence study of cadmium zinc telluride Swati Jain West Virginia University Follow this and additional works at: https://researchrepository.wvu.edu/etd Recommended Citation Jain, Swati, "Photoluminescence study of cadmium zinc telluride" (2001). Graduate Theses, Dissertations, and Problem Reports. 1252. https://researchrepository.wvu.edu/etd/1252 This Thesis is protected by copyright and/or related rights. It has been brought to you by the The Research Repository @ WVU with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you must obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in WVU Graduate Theses, Dissertations, and Problem Reports collection by an authorized administrator of The Research Repository @ WVU. For more information, please contact [email protected]. PHOTOLUMINESCENCE STUDY OF CADMIUM ZINC TELLURIDE Swati Jain Thesis submitted to the Eberly College of Arts and Sciences at West Virginia University in partial fulfillment of the requirements for the degree of Master of Science in Physics Nancy C. Giles, Ph.D., Chair Larry E. Halliburton, Ph.D. Mohindar S. Seehra, Ph.D. Department of Physics Morgantown, West Virginia 2001 Keywords: Photoluminescence, PL, CdZnTe, CZT, Cd1-xZnxTe ABSTRACT PHOTOLUMINESCENCE STUDY OF CADMIUM ZINC TELLURIDE SWATI JAIN In this thesis, I present a detailed study of Cd1-xZnxTe crystals with 0 ≤ x ≤ 0.14 using photoluminescence (PL) spectroscopy.
    [Show full text]
  • Cadmiumzinc Telluride High Resolution Detector Technology
    Invited Paper CadmiumZinc Telluride High Resolution Detector Technology Arnold Burger, Henry Chen, Kaushik Chattopadhyay, Jean-Olivier Ndap and Stephen U. Egarievwe, Center for Photonic Materials and Devices, Department of Physics Nashville, TN 37208-3051, U. S. A. and R. B. James, Advanced Electronics Manufacturing Technologies Department, Sandia National Laboratories, Livermore, CA 94550 ABSTRACT Electrode contacting on semiconductor radiation detectors has been a topic of active interest in many recent investigations. Research activities have focused on the morphology and chemistry of modified surfaces using sophisticated preparation techniques and employing characterization methods that are able to discriminate between surface and bulk effects. From an applied point of view, the detector fabrication technology involves a series of fabrication steps which can be optimized. Results of an ongoing effort to improve the performance of high resolution Cd,Zn1Te (CZT) spectrometers by addressing wafer surface preparation, electrode deposition and contact passivation are described.. Keywords: Cadmium zinc telluride, detector fabrication, contacts, surface preparation 1. INTRODUCTION There is presently a widespread need for room temperature gamma and X-ray imaging capability for both medical and industrial applications. Solid state CZT arrays offer the possibility of reducing the weight of existing nuclear medicine cameras based on scintillators and photomultiplier. CZT combines the room temperature operation with the energy resolution that approaches that ofthe cryogenically cooled Ge and Si detectors. However, CZT detectors are still in very limited use, mainly due to the limited availability oflow price and defect free material. Recently, studies aimed at a better understanding of the electric contact formation process were performed and it was shown that in many cases, in particular when high resolution, low active volume detectors, the performance of the detectors is limited by surface preparation, contacting and device passivation.
    [Show full text]
  • SURFACE and BULK DEFECTS in CADMIUM ZINC TELLURIDE and CADMIUM MANGANESE TELLURIDE CRYSTALS by Oluseyi Stephen Babalola Disserta
    SURFACE AND BULK DEFECTS IN CADMIUM ZINC TELLURIDE AND CADMIUM MANGANESE TELLURIDE CRYSTALS By Oluseyi Stephen Babalola Dissertation Submitted to the Faculty of the Graduate School of Vanderbilt University In partial fulfillment of the requirements For the degree of DOCTOR OF PHILOSOPHY In Interdisciplinary Materials Science December, 2009 Nashville, TN Approved: Professor Leonard C. Feldman Professor Arnold Burger Professor Timothy Hanusa Professor Jim Wittig Professor Bridget Rogers Doctor Ralph James ©Copyright by Oluseyi Stephen Babalola December, 2009. ii Ope ni fun Olodumare To Mary, Tolu, eleven siblings iii ACKNOWLEDGEMENT I owe my deepest gratitude to Professor Leonard Feldman, my advisor and chair of my Ph.D. committee for his encouragement, supervision and support from my early years in Vanderbilt through my preliminary and qualifying examinations to the concluding level of this thesis. I am very grateful to Professor Arnold Burger, my co-advisor, for mentoring and supporting me through my advanced degree programs. I am also grateful to Doctor Ralph James for providing me with the opportunity to learn and do research with the brightest minds and world-class equipment. I specifically thank these three aforementioned mentors for creating the atypical inter-institutional collaboration involving Vanderbilt University, Fisk University and Brookhaven National Laboratory towards advancing the science of room temperature nuclear detector materials, and in so doing, expanding my horizon and providing me with an extensive list of scientific equipment and the golden opportunity of working with the best scientists in this field. I would also like to acknowledge the other members of my committee; Professor Timothy Hanusa, Professor Bridget Rogers and Professor James Wittig for their tutoring and availability to help.
    [Show full text]
  • Synthesis and Characterization of Znte Nanoparticles
    Nepal Journal of Science and Technology (Nepal J Sci Tech) (2016), 17(1): 1–3 © 2016 by Nepal Academy of Science and Technology NJST Synthesis and characterization of ZnTe nanoparticles Sujan Dhungana#, Bhoj Raj Poudel, & Surendra K. Gautam Original Article Department of Chemistry, Tri-Chandra Multiple Campus, Tribhuvan University, Kathmandu, Nepal KEYWORDS ABSTRACT Electron diffraction; semiconductor In this work, we report the ZnTe semiconductor nanoparticles (NPs) prepared by nanoparticles; transmission electron aqueous chemical precipitation method using the tellurium precursor solution microscopy; X-ray diffraction; ZnTe with different zinc compounds. Three batches of ZnTe NPs were synthesized to study the effect of dilution on the size and phase purity of ZnTe. The influence of #CORRESPONDENCE source compounds and concentrations of the size and structure of NPs were studied. ZnTe NPs have great applications as field-effect transistors and photodetectors. Tel: +977 1 4439850 The existing controversy regarding the crystalline structure of ZnTe NPs, E-mail: [email protected] whether it is cubic or hexagonal, has been resolved using X-ray Diffraction (XRD) data. The ZnTe NPs possess cubic structure, which is also confirmed by ARTICLE HISTORY Electron Diffraction (ED) pattern. The average particle size determined from Received 25 Feburary 2016 XRD data with the help of Debye-Scherrer equation is about 6 nm. The particle Revised 25 May 2016 size can be further verified by Transmission Electron Microscopy (TEM) studies. Accepted 18 June 2016 ACADEMIC EDITOR Gan B. Bajracharya 1. Introduction Zinc telluride is a Group II-VI compound semiconductor ZnTe nanoparticles were synthesized from different sources with a direct band gap of 2.26 eV (Ersching et al.
    [Show full text]
  • (A) Lanthanide (Ln) Zinc Telluride by Means of Experimental and Quantum-Chemical Techniques
    crystals Article Revealing the Bonding Nature in an ALnZnTe3-Type Alkaline-Metal (A) Lanthanide (Ln) Zinc Telluride by Means of Experimental and Quantum-Chemical Techniques Katharina Eickmeier and Simon Steinberg * Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany; [email protected] * Correspondence: [email protected]; Tel.: +49-241-80-92075 Received: 17 September 2020; Accepted: 8 October 2020; Published: 10 October 2020 Abstract: Tellurides have attracted an enormous interest in the quest for materials addressing future challenges, because many of them are at the cutting edge of basic research and technologies due to their remarkable chemical and physical properties. The key to the tailored design of tellurides and their properties is a thorough understanding of their electronic structures including the bonding nature. While a unique type of bonding has been recently identified for post-transition-metal tellurides, the electronic structures of tellurides containing early and late-transition-metals have been typically understood by applying the Zintl Klemm concept; yet, does the aforementioned formalism actually − help us in understanding the electronic structures and bonding nature in such tellurides? To answer this question, we prototypically examined the electronic structure for an alkaline metal lanthanide zinc telluride, i.e., RbDyZnTe3, by means of first-principles-based techniques. In this context, the crystal structures of RbLnZnTe3 (Ln = Gd, Tb, Dy),
    [Show full text]
  • The Cadmium Zinc Telluride Imager on Astrosat
    J. Astrophys. Astr. (June 2017) 38:31 © Indian Academy of Sciences DOI 10.1007/s12036-017-9447-8 Review The Cadmium Zinc Telluride Imager on AstroSat V. BHALERAO1, D. BHATTACHARYA1, A. VIBHUTE1,P.PAWAR1,2,A.R.RAO3,∗, M. K. HINGAR3, RAKESH KHANNA3,A.P.K.KUTTY3, J. P. MALKAR3,M.H.PATIL3, Y. K. ARORA3, S. SINHA3,P.PRIYA4, ESSY SAMUEL4, S. SREEKUMAR4, P. VINOD4, N. P. S. MITHUN5, S. V. VADAWALE5, N. VAGSHETTE1,5, K. H. NAVALGUND6, K. S. SARMA6, R. PANDIYAN6, S. SEETHA6 and K. SUBBARAO6 1Inter University Centre for Astronomy and Astrophysics, Pune 411 007, India. 2S. R. T. M. University, Nanded 431 606, India. 3Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. 4Vikram Sarabhai Space Centre, Thiruvananthapuram 695 022, India. 5Physical Research Laboratory, Ahmedabad 380 009, India. 6ISRO Satellite Centre, Bangalore 560 017, India. ∗Corresponding author. E-mail: [email protected] MS received 11 August 2016; accepted 29 December 2016; published online 19 June 2017 Abstract. The Cadmium Zinc Telluride Imager (CZTI) is a high energy, wide-field imaging instrument on AstroSat. CZTI’s namesake Cadmium Zinc Telluride detectors cover an energy range from 20 keV to > 200 keV, with 11% energy resolution at 60 keV. The coded aperture mask attains an angular resolution of 17 over a 4.6◦× 4.6◦ (FWHM) field-of-view. CZTI functions as an open detector above 100 keV, continuously sensitive to GRBs and other transients in about 30% of the sky. The pixellated detectors are sensitive to polarization above ∼100 keV, with exciting possibilities for polarization studies of transients and bright persistent sources.
    [Show full text]
  • Backgrounds in Cadmium Zinc Telluride (Czt) Gamma-Ray Spectrometers for Planetary Science
    43rd Lunar and Planetary Science Conference (2012) 1284.pdf BACKGROUNDS IN CADMIUM ZINC TELLURIDE (CZT) GAMMA-RAY SPECTROMETERS FOR PLANETARY SCIENCE. R. C. Reedy1, T. H. Prettyman1, and N. Yamashita1, 1Planetary Science Institute, Suite 106, 1700 E Fort Lowell, Tucson, AZ 85719. <reedy@ psi.edu>. Summary: The gamma rays made by space ener- capture of an orbiting electron or by an isomeric (or getic particles in CdZnTe detectors, such as those on internal) transition in one nucleus [2]. the NASA Dawn Mission, are listed and discussed. Production of prompt gamma rays during events Introduction: Gamma-ray detectors in space have with high fluxes of solar protons was not considered backgrounds in their spectra because of cosmic-ray because the energy loss of the proton in the detector interactions with the detector materials. A good under- will sum with most gamma rays. standing of all those backgrounds, especially discrete- Being a minor component, only the strongest gam- energy peaks, in a gamma-ray spectrometer (GRS) is ma rays are given for Zn. needed to correctly analyze the measured gamma-ray Peaks inside CZT Detectors: Almost all of the spectra from a planetary object of interest. Most back- peaks made in CZT by these gamma rays (individually grounds contribute to the continuum, but some are in or by summing) are <2 MeV, and therefore could be at peaks. Some of these peaks could possibly interfere energies of many gamma rays used to map elements. with gamma rays used to determine elemental compo- Prompt neutron-induced reactions: The main sition of an object.
    [Show full text]