In this thesis, the electronic and magnetic properties of Cr doped wurtzite ZnS were studied by means of most advanced theoretical approach density functional theory (DFT) using generalized gradient approximation (GGA) functional and its correction factor GGA+U. Calculations have shown that doping of chromium at cationic sites of wurtzite zinc sulphide results in formation of a p-type semiconductor. Addition of hubbard term in the system causes an increase in band gap value and creates a gap between spin up and spin down channels for 3d states of chromium atoms.
Chromium doped ZnS possess half metallic character because of excess in majority spin carriers than minority ones. Hopping of electrons in anti-bonding states of chromium atoms refers to the ferromagnetic behavior of the material. Half metallicity and ferromagnetic nature of the chromium doped wurtzite zinc sulphide makes this material a best candidate to be used in the field of spintronics.
For the past few decades, work in semiconductor field appears to be of substantial importance in industrial world and offers a new direction to upgrade the standards of life. This novel era of semi-conductors has remake the history of science with its groundbreaking technology and has proven to be an extensively emerging field to handle even single atoms and molecules for manipulation and fabrications. In the recent years, material science has open a new window towards applicability of semiconductor devices in electronics, spintronics and many other branches of science. Presently, II-VI materials have gain much value because of their broad range of applicability in advance fields of science. These elements involve transition metals like zinc, cadmium and nonmetals like oxygen, sulphur, selenium, tellurium. Due to their wide band gap, these compounds possess shorter wavelength and used in optoelectronic devices.
TABLE OF CONTENTS
LIST OF TABLES AND FIGURES
ABSTRACT
CRAPTER 01: INTRODUCTION
1.1 Research Problem
1.2 Research Plan
CHAPTER 02: LITERATURE REVIEW
Literature Review
CHAPTER 03: THEORETICAL BACKGROUND
3.1 Energy Band Theory
3.2 Semiconductors and their Characteristics
3.3 Direct/Indirect Band Gap Semiconductors
3.4 II-VI Compound Semiconductors
3.5 Zinc Sulphide
3.6 Exchange Interaction
3.6.1 Direct Exchange Interaction
3.6.2 Indirect Exchange Interaction
3.6.2.1 Double Exchange Interaction
3.7 Jahn Teller Effect-
3.8 Techniques for Computational Study
3.9 Density Functional Theory
3.9.1 Many-Body Problems in Solids
3.9.2 Hohenburg-Kohen Theorems
3.9.2.1 First Hohenburg Kohen Theorem
3.9.2.2 Second Hohenburg Kohen Theorem
3.9.3 Kohan-Sham Equation
3.9.4 Exchange Correlational Functional
3.9.5 Local Density Approximation (LDA)
3.9.6 Local Spin Density Approximation (LSDA)
3.9.7 Generalized Gradient Approximation (GGA)
3.9.8 LDA and GGA with Hubbard Correction
3.9.9 Hybrid Functional
3.9.10 Tran-Blah Modified Becke Johnson Potential (TB-mBJ)
3.10 Basis Sets
3.10.1 Slater-Type Orbital (STO)
3.10.2 Gaussian-Type Orbital (GTO)
3.11 Amsterdam Density Functional (ADF)
CHAPTER 04: COMPUTATIONAL TECHNIQUES
4.1 ADF-BAND-
4.2 Brief Introduction to ADF-BAND
4.2.1 Features of ADF-BAND
4.2.2 Operating System for ADF-BAND
4.2.3 Electronic and Structural Parameters using ADF -BAND
4.2.4 Construction of wurtzite ZnS structure with ADF -BAND
4.2.5 Construction of a unit cell of ZnS
4.3 Computational Aspect
CHAPTER 05: RESULTS AND DISCUSSIONS
5.1 Electronic Properties
5.1.1 Chromium Doped Zinc Sulphide: 16 atoms
5.1.2 Cr Doped ZnS: 32 atoms
5.1.3 Cr Doped ZnS: 64 atoms
5.2 Conclusion
REFERENCES
PLAGIARISM REPORT BY “TURNITIN”
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