| Titre : | Experimental and DFT study on the physical properties of p-type semiconductors oxides for thermoelectric applications |
| Auteurs : | Hanna Touhami, Auteur ; Said Lakel, Directeur de thèse |
| Type de document : | Thése doctorat |
| Editeur : | Biskra [Algérie] : Faculté des Sciences Exactes et des Sciences de la Nature et de la Vie, Université Mohamed Khider, 2024 |
| Format : | 1 vol. (148 p.) / ill., couv. ill. en coul / 30 cm |
| Langues: | Anglais |
| Résumé : |
In the present work, pure and alkali doped NiO (Ni1-xAxO) and La-alkali co-doped (Ni1- 2yAyLayO) NiO thin films where (A=Li, Na and K) and (x=0.03, 0.06, 0.09, 0.125 and 0.25) and (y=0.03, 0.06) were synthesized by sol-gel spin coating method and deposited on glass substrates. XRD analysis showed that the prepared films belongs to a cubic structure with (100) plane wave as preferential growth orientation for pure and K doped NiO for small K contents and the (200) for higher K contents along with Li, Na, and La-alkali co-doped NiO thin films. The grain size decreased with the increase of the concentration of doping elements in the NiO lattice. Optical properties of the prepared films were investigated. As x increased the transparency of the prepared films decreased. Also the optical study revealed that the optical band gap tends to decrease with alkali doping and achieves minimal values with Na doping. The Urbach energy increases systematically with the decrease of the optical band gap. The resistivity measurements showed that the alkali doping and La-alkali co-doping led to a significant decrease in the resistivity values. Structural, electronic, optical and elastic properties of pure and alkali doped NiO (Ni1-xAxO) and La-alkali co-doped (Ni1-2yAyLayO) NiO thin films where (A=Li, Na and K) and (x=0.03, 0.06, 0.125 and 0.25) and (y=0.03, 0.06) were performed using the first principle method based on density functional theory. The optimization of the geometry of the studied samples revealed that lattice parameter is affected with alkali doping and La-alkali co-doping. The band structure and density of states calculations showed that doped and co-doped samples exhibited an indirect band gaps. The optical parameters: ε1(ω), ε2(ω), n(ω), k(ω), α(ω), R(ω) , L(ω) and elastic constants: ( |
| Sommaire : |
Acknowledgements Dedication Contents List of figures vii List of tables x General introduction 1 Chapter I: Literature Revue I.1. Introduction 8 I.2. The concept of semiconductor 8 I.3. Electrical conductivity in semiconductors 8 I.4. Types of semiconductors 10 I.4.1. Intrinsic semiconductors 10 I.4.2. Extrinsic semiconductors 10 I.4.2.1. n-type semiconductors 10 I.4.2.2. p-type semiconductors 10 I.5. Classification of semiconductors 11 I.5.1. Elementary semiconductors 11 I.5.2. II -VI semiconductors 11 I.5.3. Transparent metal oxides (TCOs) 11 I.5.3.1. n-type TCOs 11 I.5.3.2. p-type TCOs 12 I.6. Nickel oxide (NiO) 12 I.6.1. NiO properties 13 I.6.1.1. NiO crystallographic properties 13 I.6.1.2. Electronic properties of NiO 14 I.6.1.3. Thermal oxidation of nickel 17 I.6.1.4. Optical properties of NiO 17 I.6.1.5. Electrical properties of NiO 19 I.6.1.6. Magnetic properties 20 I.6.2. NiO applications 21 I.6.2.1. Photo-voltaic cells 21 I.6.2.2. Protective films 21 I.6.2.3. Antimicrobial activity 22 I.6.2.4. Gas sensors 22 I.6.2.5. Superconductors 22 I.6.2.6. Batteries 23 I.7. Earlier works done on alkali doped NiO based thin film: A Review 23 References 26Contents Chapter II: Experimental and Theoretical Backgrounds II.1. Experimental approach 33 II.1.1. Introduction 33 II.1.2. Physical deposition methods 33 II.1.2.1. Pulsed Laser Deposition 33 II.1.2.2. RF Sputtering 33 II.1.2.3. Thermal evaporation 34 II.1.3. Chemical deposition methods 34 II.1.3.1 Electrodeposition 35 II.1.3.2. Chemical bath deposition 35 II.1.3.3. Chemical Vapor Deposition (CVD) 36 II.1.3.4. Spray pyrolysis technique 36 II.1.3.5. Sol-gel technique 36 II.1.3.5. 1. Reaction mechanisms 38 II.1.3.5. 2. Sol-gel Transition 40 II.1.3.5.3. Drying of the gel 40 II.1.3.5.4. Thin films elaboration via sol-gel method 41 II.1.3.5.4. 1. Dip-coating 41 II.1.3.5.4. 2. Spin-coating 42 II.1.4. Characterization techniques of NiO thin films 43 II.1.4.1. Structural characterization 43 II.1.4.1.1. Crystallite size calculation 44 II.1.4.1.2. Lattice parameters calculation 44 II.1.4.1.3. Stress-Strain calculation 44 II.1.4.2. Optical Characterization 45 II.1.4.2. 1. UV-visible spectroscopy 46 II.1.4.2. 2. Measurement of optical properties 46 II.1.4.2. 2.3. Measurement of thickness 46 II.1.4.2. 2.4. Determination of the absorption coefficient 47 II.1.4.2. 2.5. Band gap and Urbach energy determination 48 II.1.4.3. Electrical properties measurements 50 II.1.4.3.1. Resistivity measurements 51Contents II.1.4.3. 2. Conductivity measurements 52 II.2. Theoretical Approach 52 II.2.1. Introduction 52 II.2.2. The Many Body Problem 53 II.2.3. Born Oppenheimer approximation 53 II.2.4. Hartree approximation 54 II.2.5. Hartree-Fock Approximation. 55 II.2.6. Density Functional Theory (DFT) 56 II.2.6.1. The Hohenberg-Kohn Theorem 57 II.2.6.2. Kohn-Sham Equations 57 II.2.6.3. Exchange-correlation energy 58 II.2.6.4. Local density approximation (LDA) 58 II.2.6.5. Local spin density approximation (LSDA) 59 II.2.6.6. Generalized Gradient Approximation (GGA) 60 II.2.6.7. DFT+U Approximation 61 II.2.7. CASTEP 62 References 64 Chapter III: Results and Discussion III.1. Introduction 68 III.2. Experimental part 68 III.2.1. Experimental procedure and characterization techniques 68 III.2.2. Results and discussion 69 III.2.2.1. Structural properties 69 III.2.2.1.1. Structural properties of Pure and Alkali doped NiO: Ni1-xAxO (A=Li, Na and K) 69 III.2.2.1.2. Structural properties of co-doped NiO Ni1-2xAxLaxO A= (Li, Na, K), (x=0.03, 0.06)78 III.2.2.2. Optical properties 80 III.2.2.2.1. Optical properties of Pure and Alkali doped NiO (Ni1-xAxO) (A=Li, Na and K) III.2.2.2.2. Optical properties of co-doped NiO Ni1-2xAxLaxO A= (Li, Na, K), (x=0.03, 0.06) III.2.2.3. Electrical properties 95 III.2.2.3.1. Electrical properties of Pure and Alkali doped NiO (Ni1-xAxO) (A=Li,Na and K)95 III.2.2.3.2. Electrical properties of co-doped NiO Ni1-2xAxLaxO A=(Li, Na, K), (x=0.03, 0.06)98 III.3. Theoretical results 100 III.3.1. Computational methods 100 III.3.2. Structural properties 101 III.3.2.1. Structural properties of pure and Ni1-xAxO (A=Li, Na and K) 101 III.3.2.2. Structural properties of Ni1-2xAxLaxO (A=Li, Na and K) 104 III.3.3. Electronic properties 105 III.3.3.1. Introduction 105 III.3.3.2. Electronic properties of pure and Ni1-xAxO (A=Li, Na and K) 106 III.3.3.2.1. Band structures of pure and Ni1-xAxO (A=Li, Na and K) 106 III.3.3.2.2. Density of states of pure and Ni1-xAxO (A=Li, Na and K) 110 III.3.3.3. Electronic properties of Ni1-2xAxLaxO (A=Li, Na and K) 115 III.3.3.3.1. Band structures 115 III.3.3.3.2. Density of states 116 III.3.4. Optical properties 119 III.3.4.1. Optical Constants 119 III.3.4.2. The dielectric function |
| En ligne : | http://thesis.univ-biskra.dz/id/eprint/6573 |
Disponibilité (1)
| Cote | Support | Localisation | Statut |
|---|---|---|---|
| TPHY/142 | Théses de doctorat | bibliothèque sciences exactes | Consultable |
