Luận văn monte carlo study of the room temperature ferromagnetism of diluted magnetic semiconductor

LIST OF FIGURES Master thesis The energy landscape of a configuration with a large number of local The equality of two specific heat curves caleiated via the febusrien of energy and the

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MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY

School of Engineering Physics

Monte Carlo study of the room-temperature

ferromagnetism of diluted magnetic semiconductors

by

HA VIET ANH

L2 L)

A thesis for master of science

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Acknowledgements

First and foremost, I would be thank/ul to Dr Dao Xuan Viet, a lecturer in Advanced Instilule for Science and Technology (AIST), Hanoi University

of Science and Technology Dr Tao has instructed me as a supervisor

since my bachelor’s thesis During a lang time, he taught me nnmerans

knowledges and skills for Monte Carlo (Mi

physics linux operating system, programing with C and Fortran language

} simulation such as statistical

data analysis etc

Especially beside academic works, he also supported financial budget for this roscarch, It is not cxaggcration to soy that Dr Dao’s enthusiastic in- structious played significant role in my achicvernents, In a word, I Lonestly appreciate wll supports und wids from Dr, Dao

Furthermore, [ also would be thankful 1 Prof Mai Suou Li and Prof Nguyen Manh Duc for supporling useful dicussions, Assoc Prof, Pham Thanh Huy for promoting this research and providing a chance to attend and present @ poster in ISPS Core-ta-Core Program, Chulalongkorn Uni-

versity, Bangkok, Thailand, Dr Nguyen Dne Trung Kien for giving a mum-

ber of helpful comments to my paper manuscripts and and Assoc Prof Nguyen Hun Lam for facilitating my research in AIST

This research was supported by the National Application-Oriented Basic

Research Program, Project No D'TDL.05-2011-NCCL and by the National

Foundation for Scicnce and Technology Development (NAEOSTED] under Project No 103,02-2011.38, [ would thack lo ICSE (Inicrnatioual Rescarch Insitute for Computational Science and Enginecring), Hanoi Universicy of Science and Technology, Vietnam for providing us with uhe CPU time Finally, [ express my thankfulness to my parcuns, siblingy and friends who have always been believing in, providing and encouraging me during the

past years

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Abstract

In faot, new materinlx are shways one of crucial issues for the development

of society Tn 1940s, the thriving of semiconductors absolutely changed the world ‘These achievments are motivation for investigating and exploring new materials with exceptional properties hems applicable m pratice,

A class of materuls named “diluted magnetic semiconductor” (DMS) has widely attrantad interest DMS combines properties of senicandnetor and

magnetic material m only ane subject Therefore, they are potential can-

didates for designing spintronics devices DMS, firstly, was considered in 1960s which derived from compound of Eu er composite compound in na- ture However posibility in application was restricted because of low Curie temperature phase transition

Recently, DMS was produced by doping transition metals (TM) into conventional semiconductors, then expect to obtain ferromagnetism and still

mniconducting propertics Some 'TM mainly used im doping arc

Among those, Mu has cspetially boou cousidered with both theoretical and experimental studies showing that Mu-doped GaAs GAN, exhihat ferromagnerism, Nevertheless, stabihry and original inter action contributing to ferramagnerism are still questionable

More recently, DMS deped with uoumaguctic light elements such as Li

Be, B, N, C were investigaled and fabricated In 2007, Lhe room Lemper-

atnre ferromagnetism was experimentaliy demanstrared for C-doped ZnO

in shallow impurity concentration regime On the theoretical side, the room-temperature ferromagnesism in C-doped ZnO has been studied by combining the first-principle calculations and the MC simularion

Tn thns thess, the ferramagnetic ordermg of Cd and JO wnrtmates de

with C impurity in low concentration regime have becn investigated by

MC simulation, To clarify the open question whether the spins oxists as continuous or discrete state, both the continuous and discrete spin models hove been considered

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Master thesis

List of Figures

Li Phase transition temperature To of various semiconductors doped Mn [5] 2 1.2 Temperature dependence of magnetization of (Ga, Mn)N farbricated by

La Temperature dependence of magnetization of C-doped ZnO farbricated

by lazer pulse enhanced method [16] sẻ 4

14 Temperature dependence magnetization of Coaloped 220 dĩ uc simu-

1.5 Temperature dependence iaghelieau jon of GaAs with different ONGE=

L.6 A unit cell of wurzite structure ‘Online source: z

21 Wiurtzite lattice o[ CdŠ, 8unfur atoms (green spheres} might be sub-

stitued by C atoms In this figure, eight different possible sites from 1

244 Spin-flip as Over-relaxation algorithm Fundamentally, 5; can change

24 The equality of two specitic heat curves calculated via the fluctuation

of energy and the temperature difference of energy formulae in C-doped

The process of exchange spin configurations corresponding to various

nN m The acceptance ratios of two temperature sets: Geametric and optimized

2.7 Replica moving of a specific replica in a measured temperature interval

Pein =105.576 (10) and Tyyq:=522.225 (K) with size L=20 a) Geometric temperature set, b) Optimized temperature sct The horizontal line

marks bottle-neck point of goomctric avveptance ratios, reer eee 1S

HA VIET ANH iii ENGINEERING PHYSICS

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LIST OF FIGURES Master thesis

The energy landscape of a configuration with a large number of local

The equality of two specific heat curves caleiated via the febusrien

of energy and the temperature difference of energy formulae in C-doped CaS system in discrete spin model a) L=i2 b) L=12

The temperature-dependence of energy per spi in two-dimenstion Ising

Specific heat Oy as a function of teraperature in the [Heisenberg model

Temperature dependence of magnetization in q-state spin model The

inset: magnetic susceptibility

‘Tomperature dependence of Binder ration in q-state spin model

Temperature dependeuce of spevihe beat in g-state spin model

Tomperature dependence of magnetization in q-state spin model The

‘Tomperature dependence of Binder parameter in q-state spin model

Temperature dependeuce of specific beat in g-state spit model

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Master thesis

List of Figures

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CONTENTS: Master thesis

42 C-doped ZnO

4.2.1 Tlesenberg model 42.2 q-state spin model Summary

A Specific heat formula

B Magnetic susceptibility formula

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42 C-doped ZnO

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42 C-doped ZnO

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Master thesis

Chapter 1

Introduction

Diluted magnetic semiconductors (DMS) are materials that simultancously hold both

magnetic utd semivonducting properties when host semicunducwor duped with w low

concentration of impurity These materials have be

studied widely with a purpose

of designing new device generation possessing varions improvements like nonvolaril

saving energy comsumed, integrated density enlargement ete [1, 2]

1.1.1 History

De facto, the material combining both magnetic and semivonducting properties was investigaled from 1960s with name ‘Early magnetic semiconductor’ and from 1980s the later class exactly called ‘Dihuted magnetic semiconductor’

Barly magnetic semiconductor

This generation material might he classified into two groups:

« Chalcogenide spinel: AL,X, (A, 4 are metals and X are elements belonging to

group VEIL such as $, So, Te) For cxample CdOralz, FcOraE„, MnOt,l,

CoOr,S/, QuOr,5,, ZnCr,Be,, CdOr,Sc¿, IIgCt,Sc,, CuCrySes

« Europium chaleogemde; EuX (X are elements like Q, 3, 8e, Te)

All these materials are usually n-type semiconductor and ils wagnetic origin derives

from strong interaction betwoun curricrs (cluctron) with magnetic moment of ions which

have unfilled d or f subshell Motion of carriers and magnelic order of ions impact

on each other In many materials, energy of electrons can be minimized when they

completely exist in ferromagnetic order state [:]

Tlowever it is really substantial drawback because in these materials, phase tran-

sition temperature is below 100K Moreover, the processing is also another difficulty

HA VIET ANH 1 ENGINEERING PHYSICS

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Master thesis

Chapter 1

Introduction

1.1.1 History

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Master thesis

List of Figures

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Master thesis

List of Figures

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42 C-doped ZnO

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Master thesis

List of Figures

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Chapter 1 Introduction Master thesis

because of stringent demand for high quality of crystal [4] ‘Therefore, potential applications in this material generation is practically imposible

Diluted magnetic semiconductor-DMS

This generation based on conventional semiconductors doped with impurities in low

concentration regime (<20%)

Semiconductors mainly are two types of compound semiconductors: AyByr and

Ay By [4] The impurities, initially, were TM such as Cr, Mn, Fe, Co, Ni, Cu Never-

theless, other light elements like Li, Be, C, N have also attracted wide interests recently

Definitely, Curie temperature Te above room-temperature is an essential requirement Acorrding to Dielt [5], GaN and ZnO are two ideal host materials that can satisfy Te >

300K (Fig 1.1)

10 100 1000

T, (K)

7 Dit ta, Since 00, Pry ev 82001

Figure 1.1: Phase transition temperature Te of various semiconductors doped Mn (5)

1.1.2 Review of research

On the whole, research directions in DMS are factually diverse The essential attention

relates to electronic, optical, magnetic properties performed in both experimental and

theoretical studies,

For example, the photocatalytic activity in nanoparticle and nanosheet of C-doped ZnO was confirmed [6, 7] On the other side, TM-doped zinc chalcogenides such as Cr-doped ZnO, Cr-doped ZnS ete were also investigated for lazer emission applications

|8 9|

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300K (Fig 1.1)

10 100 1000

T, (K)

|8 9|

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Master thesis

Chapter 1

Introduction

1.1.1 History

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Master thesis

Chapter 1

Introduction

1.1.1 History

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Master thesis

Chapter 1

Introduction

1.1.1 History

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Chapter L Introduction Master thesis

Furthermore electronic charaeteristies like band structure in C-doped CdS [LO],

resistivity in transition metal-doped ZnO [1L, transpart property [12 13] quantum

confinement, [14] in Mn-doped GaAs ete were studied

Farticularly, this study has focused on magnetic property To specify, overview of this aspect would be presented more clearly below

1.2.1 Experiment

There have heen many works focusmg on processing and investigating characteristics

of DMS The main subjects are III-V and IL-VI semiconductors doped with TM such

as (Ga,Mn)As (Ga.MnjN, With Molecular Beam Epitaxy (MIBE} method, the fab- rication became more convenient when impurity concentration can reach to 10 % or higher and quality of DMS Lily w improved signifieuntly [15] The Fig 1.2 displays muagnetizalion aguinty temperature of (Gag g)Mupe)N

duped ZnO film [16] The temperature dependence of magnetization showed in the

Fig 13 demonsteated that 7c is, remarkably, highcr then room-temperature

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1.2.1 Experiment

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Master thesis

List of Figures

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300K (Fig 1.1)

10 100 1000

T, (K)

|8 9|

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1.2.1 Experiment

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Master thesis

Chapter 1

Introduction

1.1.1 History

Tiêu đề	Monte Carlo Study of the Room-Temperature Ferromagnetism of Diluted Magnetic Semiconductors
Tác giả	Ha Viet Anh
Người hướng dẫn	Dr. Dao Xuan Viet
Trường học	Hanoi University of Science and Technology
Chuyên ngành	Engineering Physics
Thể loại	Thesis
Năm xuất bản	2014
Thành phố	Hanoi

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