| Titre : | The role of pH on the synthesis of a passivation layer comprising MgO-ZnO alloys |
| Auteurs : | Nadjat Chaouch, Auteur ; Said Benramache, Directeur de thèse ; 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, 2023 |
| Format : | 1 vol. (109 p.) / couv. ill. en coul / 30cm |
| Langues: | Anglais |
| Langues originales: | Anglais |
| Mots-clés: | MgO ; MgO-ZnO ; Thin films ; pH solution ; Spray technique |
| Résumé : |
The aim of this work is to prepare thin films of MgO and alloys MgO-ZnO by the spray pyrolysis technique. and to study the effect of different experimental parameters on the fundamental properties of thin films, The parameters investigated are (substrate temperature, molarity, and pH). Firstly, we prepared the MgO thin films on a glass substrate at 450°C at different MgO concentrations (0.05, 0.10, 0.15, and 0.2 mol.l-1). the MgO thin films show a cubic structure with a strong (002) preferred orientation and a maximum crystallite size of 21.4 nm attained of sprayed film at 0.2 mol.l-1.Good transmission was found in MgO thin film with the lowest molarity. The transmission of MgO thin films decreases rapidly as the wavelength increases in the range of (300-400) nm and then increases slowly at higher wavelengths. The band gap of MgO thin films decreases as the molarity increases and the band gap values range between 4.8-4.3 eV. The electrical resistance of our films is in the order of 2.107Ω. Secondly, the MgO Thin Films have been grown on glass substrates at 450°C by various pH solution values (2.5; 5;6.8; 8.3, and 10 pH). The MgO thin films have a strong preferential crystallinity with a cubic structure with a high (200) phase, the minimum value of crystallite size 9.9 nm is attained of deposit MgO thin film at 450 °C with 10 of pH. The optical transmission spectra showed all the sprayed MgO thin films are transparent within the visible wavelength region. The band gap of MgO thin films decreases from 3.91 to 3.7 eV as the pH increases from 2.5 to 6.8, and the Urbach energy was increased. The surface morphology by SEM indicated that in the MgO prepared with pH = 5 and 6.80 the grains become nearly spherical and bigger, and for the pH increased to pH =10, showing spherical particles and smaller, this may be when coalescence occurs. The thin film obtained with 2.5 pH has a lower electrical resistance. Thirdly, Zn 0.5Mg 0.5O thin films have been grown on glass substrates at 450°C by various pH solution values (2.5; 7.10, and 8.30 pH). The Zn 0.5Mg 0.5O thin films were observed in high crystallinity with a cubic structure with a strong orientation preferential at (200) , corresponding to the maximum value of crystallite size 72.28 nm attained of deposit Zn0.5Mg0.5O thin film at 450 °C with 8.30 of pH. The optical transmission spectra showed all the sprayed Zn 0.5Mg 0.5O thin films are transparent within the visible wavelength region. The band gap of Zn 0.5Mg 0.5O thin films increases from 3.77 to 4.09 eV as the pH increases, The surface morphology of the Zn 0.5Mg 0.5O appears at pH=2.5 big grains sphere and rod-like, whereas at pH=7.10 and 8.30 the grains become nearly spherical. The thin film obtained with 2.5 and 7.10 pH has a lower electrical resistance. |
| Sommaire : |
Acknowledgements I Dedication II General Introduction 2 CHAPTER I Introduction and Literature Review I.1.Introduction 6 I.2.Magnesium oxide (MgO) 6 I.3.Zinc oxide (ZnO) 8 I.4. Physical Properties of MgO , ZnO and MgO-ZnO 8 I.4.1. Structural Properties of MgO , ZnO and MgO-ZnO Synthesized In Different Conditions 9 A) Preferred orientation 10 B) The crystallite size 11 C) Lattic parameter 13 D) Strain 13 I.4.2. Optical Properties Of MgO, ZnO, And MgO-ZnO Synthesis In Different Conditions 14 A)Refractive index 18 I.4.3. Electrical Properties of MgO, ZnO, and MgO-ZnO Synthesized In Different Conditions. I.5. Application of MgO And ZnO 21 II.6. Conclusion 23 References CHAPTER II Elaboration and Characterization Techniques 30 II.1. Introduction 31 II.2. Thin Film Deposition Methods 32 II.3. Pyrolysis spray technique (PS) 32 II.4.Advantages of The spray pyrolysis technique 35 II.5.Disadvantage of The Spray pyrolysis technique 47 II.6. Experimental details 36 II.7.Study of Various Concentrations on MgO thin film 36 II.7. 1.Preparation of the solution 36 II.7. 2.Preparation of the films 36 II.8:Effect of pH solution on MgO thin film 38 II.7.1.Preparation of solution 39 II.7.2.Preparation of the films 39 II.9. Influence of pH solution on Zn0.5Mg0.5O thin film 40 II.9.1.Preparation of solution 40 II.9.2.Preparation of the films 41 II.10. Characterization Techniques 42 II.10.1 Structural characterization 42 II.10.1.a. Analysis of XRD Data 43 II.10.1.b.Identification of phases 43 II.10.1.c.Determination of Crystallite Size from XRD Data 44 II.10.1.d.Determination of Lattice Parameter 45 II.10.2. Optical characterization 46II.10.2.1. Band Gap Calculations 47 II.10.2.2. Disorder calculating (Urbach Energy) 48 II.10.3 Morphological characterization 49 II.10.3.1. Scanning electron microscope coupled with microanalysis (SEM/EDX) 50 II.10.4. Fourier transforms infrared spectroscopy (FTIR) 50 II.10.5. Electrical characterization 52 II.11. Conclusion 53 References 54 CHAPTER III Study physical properties of the MgO thin films by various concentrations 56 III.1.Introduction 57 III.2. Results and discussion 57 III.2.1.Study structural properties 57 III.2.2. Study Optical properties 59 III.2.3. Study electrical properties 63 III.3. Conclusion 65 References 66 CHAPTER IV Effect of pH Solution on the Properties of MgO Thin Films 70 IV.1. Introduction 71 IV.2. Results and discussion 79 IV .2.1. Structural properties of MgO thin films 71 IV.2.2. Optical properties of MgO thin films 76 IV.2.3.Morphology properties of MgO thin films 81IV.2.4. Electrical properties of MgO thin films 83 IV.3. Conclusion 84 References 86 CHAPTER V Influence Of pH On The Properties Zn0.5Mg0.5O Thin Films 89 V.1. Introduction 90 V.2. Results and discussion 90 V.2.1. Influence of pH on structural properties of Zn 0.5Mg 0.5O alloys. 90 V.2.2. Influence of pH on optical properties Zn 0.5Mg 0.5O alloys 94 V.2.2.a. Energy gap (Eg) 96 V.2.2.b. Urbach energy 97 V.2. 3.Fourier transform infrared (FTIR) spectroscopic analysis 99 V.2.4. Influence of pH on Morphological properties Zn 0.5Mg 0.5O thin films 100 V.2.5. Influence of pH on Electrical properties Zn 0.5Mg 0.5O thin films 102 V.4.General conclusion and perspectives 106 Abstract 110 111ملخص Resume 112 |
| Type de document : | Thése doctorat |
| En ligne : | http://thesis.univ-biskra.dz/6152/1/these%20chaouch%20nadjat.pdf |
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| Cote | Support | Localisation | Statut |
|---|---|---|---|
| TCH/104 | Théses de doctorat | bibliothèque sciences exactes | Consultable |
