Study of effects of silver incorporation on electrical and optical properties of tco thin films

VIETNAM NATIONAL UNIVERSITY, HANOI VJU VIETNAM JAPAN UNIVERSITY TRAN NGOC LAN Study of effects of silver incorporation on electrical and optical properties of TCO thin films MASTER THESIS Submitted in partial fulfillment of the requirement for the degree of Master of Nanotechnology Hanoi, July 2018 VIETNAM NATIONAL UNIVERSITY, HANOI VJU VIETNAM JAPAN UNIVERSITY TRAN NGOC LAN Study of effects of silver incorporation on electrical and optical properties of TCO thin films Submitted in partial fulfillment of the requirement for the degree of Master of Nanotechnology Supervisors: Dr Nguyen Tran Thuat Dr Hoang Ngoc Lam Huong Hanoi, July 2018 ACKNOWLEDGEMENTS I would like to express deep gratitude to my first supervisor Dr Nguyen Tran Thuat, Nano and Energy Center, VNU University of Science, Vietnam National University, Hanoi, who is a teacher – scientist has been directly guiding and helping me to finalize this thesis During the implementation of this thesis, I have received much useful scientific knowledge from him I especially would like to sincerely thank to my second supervisor Dr Hoang Ngoc Lam Huong, who has enthusiastically helped me to perform experiments to get the most accurate results I am really grateful to her for all her supports and encouragement Her ideas and suggestions were extremely useful to get this thesis to its final shape I would like to sincerely thank Dr Pham Tien Thanh, Vietnam Japan University, Vietnam National University - Hanoi, who helped me to use the Alpha Step profilometer I would like to sincerely thank Mr Luu Manh Quynh, Center of Materials Science, VNU University of Science, Vietnam National University, Hanoi - who helped me to use the UV-Vis spectrophotometer I would like to sincerely thank Ms Le Hac Huong Thu, RIKEN Center for Advanced Photonics, Innovative Photon Manipulation Research Team, Saitama, Japan, who helped me to analyze some results I would like to thank all the teachers and college students at the Nano and Energy Center, VNU University of Science, those who always create the most favorable conditions to finish this my thesis I would like to thank all the teachers and students at Vietnam Japan University, Vietnam National University, Hanoi I would like to thank project Science and Nano Technology, Vietnam National University, Hanoi (VNU) has created favorable conditions on equipment in the implementation this thesis Finally, I extend my sincere to thank to all my friends and my family, those who provide support, encouragement and help me during the learning as well as during the research and the completion of this thesis Hanoi, July 16th , 2018 Table of Contents INTRODUCTION 1.1 Transparent conductive oxides 1.1.1 Main applications of TCO materials 1.1.2 Trends in the development of TCO materials 1.1.3 A quantitative figure of merit (FOM) of TCO materials 1.2 Niobium-doped titanium oxide 1.2.1 Structural properties 1.2.2 Electrical properties 1.2.3 Optical properties 1.3 CuAlxOy 10 1.3.1 Structural properties 12 1.3.2 Electrical properties 15 1.3.3 Optical properties 16 1.4 Effects of silver incorporation on TCO thin films 17 1.5 Aim of work 19 EXPERIMENTS 21 2.1 Co-sputtering methods 21 2.2 Preparation of sample before sputtering and sputtering 27 2.3 Incorporation of silver in TNO 31 2.4 Incorporation of silver in CuAlxOy 32 2.5 Characterization methods 33 2.5.1 Thicknesses measurement 33 2.5.2 4-point probe measurement 34 2.5.3 Thermal coefficient of resistance measurement 35 2.5.4 UV-VIS measurement 35 RESULTS AND DISCUSSIONS 38 3.1 Effect of silver concentration on TNO properties 38 3.1.1 Thickness of thin films 38 3.1.2 Optical properties 39 3.1.3 Electrical properties 47 3.1.4 FOM 50 3.2 Efffect of silver concentration on CuAlxOy properties 52 3.2.1 Thickness of thin films 52 3.2.2 Optical properties 54 3.2.3 Electrical properties 58 3.2.4 FOM 65 CONCLUSION 67 REFERENCES 68 LIST OF FIGURE Figure The shape and the color of the crystalline anatase (a), rutile (b), brookite (c) and TiO2 powder (d) [14] Figure Crystal structures of anatase (a), rutile (b) and brookite (c) [14] Figure Unit cell structure of AgAlO2 [65] 12 Figure Unit cell structure of CuAlO2 [66] 12 Figure Schematic representation of the delafossite structure (ABO2) The gray polyhedral and black spheres represent edge-shared B3+O6 distorted octahedral and linearly coordinated A+ cations, respectively [67] 13 Figure The general operating principle of the sputtering method [92] 22 Figure Principle of magnetron sputtering [93] 24 Figure Four-gun sputtering machine SYSKEY SP-01 at the cleanroom of Nano and Energy Center 27 Figure The substrate cleaning solution: acetone, ethanol, acid H2SO4 and H2O2 28 Figure 10 The targets for sputtering 28 Figure 11 CG Substrates were hold on the holder 29 Figure 12 Substrates were loaded into chamber 29 Figure 13 Simulation figure of co-sputtering process 30 Figure 14 Simulation diagram of TNO thin films co-sputtering process 32 Figure 15 Simulation diagram of CuAlxOy thin films co-sputtering process 33 Figure 16 The Alpha Step profilometer at Vietnam Japan University’s laboratory 34 Figure 17 The 4-point probe Jandel at Clean Room, Nano and Energy Center, Hanoi University of Science 34 Figure 18 The Self-designed temperature dependent resistance measurement system 35 Figure 19 The Ultraviolet–visible spectroscope or ultraviolet-visible spectrophotometry (UV-Vis) at Center for Materials Science, Hanoi University of Science 36 Figure 20 Schematic UV-Vis measurement of samples 37 Figure 21 The thickness of TNO thin films depended on silver sputtering time 38 Figure 22 Effect of annealing time to the transparent of TNO-0s Ag thin films 39 Figure 23 Effect of annealing time to the transparent of TNO-30s Ag thin films 40 Figure 24 Effect of annealing time to the transparent of TNO-60s Ag thin films 41 Figure 25 Effect of annealing time to the transparent of TNO-90s Ag thin films 42 Figure 26 Effect of silver sputtering time to the transparent of TNO thin films, which were annealed in 15min 43 Figure 27 Effect of silver sputtering time to the transparent of TNO thin films, which were annealed in 30min 44 Figure 28 Effect of silver sputtering time to the transparent of TNO thin films, which were annealed in 60min 45 Figure 29 Effect of annealing temperature to the transparent of TNO-60s Ag thin films 46 Figure 30 Effect of annealing time to the conductivity of TNO thin films 47 Figure 31 Effect of annealing temperature to the conductivity of TNO thin films 48 Figure 32 Effect of annealing temperature to the FOM of TNO thin films 50 Figure 33 Effect of annealing time to the FOM of TNO thin films 51 Figure 34 The thickness of CuAlxOy thin films depended on sputtering power of copper 52 Figure 35 The thickness of CuAlxOy thin films depended on silver sputtering time 53 Figure 36 Effect of sputtering power of copper to the transparent of CuAlxOy thin films 54 Figure 37 Effect of silver sputtering time to the transparent of CuAlxOy-Cu 60W thin films 55 Figure 38 Effect of silver sputtering time to the transparent of CuAlxOy-Cu 80W thin films 56 Figure 39 The resistance depended on temperature of CuAlxOy thin films 58 Figure 40 The resistance depended on temperature of Ag doped CuAlxOy-Cu 60W thin films 59 Figure 41 The resistance depended on temperature of Ag doped CuAlxOy-Cu 80W thin films 60 Figure 42 The TCR and the conductivity of CuAlxOy thin films depended on sputtering power of copper 61 Figure 43 The TCR and the conductivity of CuAlxOy-Cu 60W thin films depended on silver sputtering time 62 Figure 44 The TCR and the conductivity of CuAlxOy-Cu 80W thin films depended on silver sputtering time 63 Figure 45 The FOM of CuAlxOy thin films depended on sputtering power of copper 65 Figure 46 The FOM of Ag doped CuAlxOy thin films depended on silver sputtering time 66 Figure 47 Resistivity vs temperature plot for a) Metal b) Semiconductor and c) Superconductor 83 Figure 48 Two-wire resistance measurement schematic 84 Figure 49 Four-wire resistance measurement configuration 85 Figure 50 Diagram of 4-point probe 85 Figure 51 A simplified schematic for the design process and the corresponding temperature diagram 87 Figure 52 Thermal coefficient of resistance measurement system 88 Figure 53 Schematic diagram of the Thermostat and Temperature Measurement 90 Figure 54 Schematic diagram of the Peltier Controller 91 Figure 55 The operation principle and the symbolic meaning of TEC1-12706 93 Figure 56 The TEC1-12706 performance specifications 94 Figure 57 Keithley Model 2400 Series Source Meter specifications 95 Figure 58 Transmission spectrum of a sample thin film 98 LIST OF TABLE Table Some basic physical parameters of TiO2 anatase, rutile and brookite phase [17] Table Optical band gap values estimated from the transmittance and reflectance spectra of TNO thin films [39] 10 Table Some typical values for air at different pressures at room temperature [94] 25 Table The list of TNO samples 31 Table The list of CuAlxOy samples 32 Table Average transmittance of CuAlO2 thin films in the visible range 57 Table Resistivity of various materials 83 In our derivations for this section, we assume that the metal tip is infinitesimal and samples are semi-infinite in lateral dimension For bulk samples where the sample thickness t >> s, the probe spacing, we assume a spherical protrusion of current emanating from the outer probe tips The differential resistance is: 𝑑𝑥 ( ) 𝐴 𝛥 where A is the area of the half sphere with radius x We carry out the integration between the inner probe tips (where the voltage is measured): where probe spacing is uniformly s Due to the superposition of current at the outer two tips, R = Thus, I arrive at the expression for the bulk resistivity: ∫ - 𝑑𝑥 2𝜋𝑥 2𝜋 ( 𝑥 )| 2𝑠 2𝜋 Thin Sheet For a very thin layer (thickness t