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Structural, Optical and Electrical Characterization of Indium Tin Oxide and Aluminum Nitride Thin Films for Gas Sensing Application

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Structural, Optical and Electrical Characterization of Indium Tin Oxide and Aluminum Nitride Thin Films for Gas Sensing Application STRUCTURAL, OPTICAL AND ELECTRICAL CHARACTERIZATION OF INDIUM TIN OXIDE AND ALUMINUM NITRIDE THIN FILMS FOR GAS SENSING APPLICATION THESIS SUBMITTED TO BHARATHIDASAN UNIVERSITY, TIRUCHIRAPALLI FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY IN PHYSICS by V.VASANTHI PILLAY, M.Sc., M. Phil Ref : 25874/Ph.D.1/P.T./Physics/Oct.2006/Confir./Date:26.05.2009 Under the guidance of Dr. K. VIJAYALAKSHMI, M.Sc., M. Phil., B.Ed., Ph.D., PG and Research Department of Physics Bishop Heber college (Autonomous) (Nationally Reaccredited at the A+ level by NAAC) (Recognized by UGC as college with potential for excellence) Tiruchirappalli – 620 017 April - 2012 PG and Research Department of Physics Bishop Heber College (Autonomous) (Nationally Reaccredited at the A+ level by NAAC) (Recognized by UGC as college with potential for excellence) Tiruchirappalli- 620 017 Dr. K. VIJAYALAKSHMI, M.Sc., M.Phil., B.Ed., Ph.D., Office : 0091-431-2770136 Assistant Professor Resi : 0091-431-2770755 Mobile : +919994647287 Email : [email protected] CERTIFICATE This is to certify that the thesis entitled “STRUCTURAL, OPTICAL AND ELECTRICAL CHARACTERIZATION OF INDIUM TIN OXIDE AND ALUMINUM NITRIDE THIN FILMS FOR GAS SENSING APPLICATION” submitted by V.Vasanthi pillay, (Ref: 25874/Ph.D.1/P.T./Physics/Oct.2006/Confir./Date:26.05.2009) is a bonafide record of research work done by her under my guidance in the Department of Physics, Bishop Heber College, Tiruchirappalli, and that the thesis has not previously formed the basis for the award to the candidate of any degree, diploma, associateship, fellowship or any other similar title. The thesis is the outcome of personal research work done by the candidate under my overall supervision. Station : Tiruchirappalli (Dr. K. VIJAYALASKHMI) Date : DECLARATION I hereby declare that the thesis entitled “STRUCTURAL, OPTICAL AND ELECTRICAL CHARACTERIZATION OF INDIUM TIN OXIDE AND ALUMINUM NITRIDE THIN FILMS FOR GAS SENSING APPLICATION” submitted by me for the degree of Doctor of Philosophy is the record of work carried out by me under the guidance and supervision of Dr. K. Vijayalakshmi, Assistant Professor, Department of Physics, Bishop Heber College, Tiruchirappalli and had not formed the basis for the award of any degree, diploma, associateship, fellowship or any other similar titles of this or any other University and other similar institution of higher learning. Place :Tiruchirappalli (V.VASANTHI PILLAY) Date : PREFACE The main purpose of this work is to study and develop new materials for gas sensing elements starting from the knowledge in thin film production using magnetron sputtering. The structure of this report is summarized below. The first chapter gives a brief introduction to the need and importance of gas sensor in the contest of current status, its implication at many different levels in our society, necessity of hydrogen and nitrogen gas sensor etc. The general approach to gas sensor, the classification of gas sensor and the characteristics of gas sensor have been discussed in this chapter. The second chapter describes the material used for gas detection. The properties of ITO and AlN are discussed in detail in this chapter. The third chapter explains dc/rf sputtering process and sputtering chamber used for thin film preparation in detail. The various instrumentation techniques used to characterize ITO and AlN thin films are also discussed in this chapter. The fourth chapter explains the optimization of ITO thin film, and the structural, optical and electrical characterization of the prepared ITO film are discussed in this chapter. Fifth chapter explains the optimization of AlN thin films, and the structural, optical and electrical properties are discussed in this chapter. Sixth chapter presents the detailed fabrication of gas sensing chamber used to sense various gases. The gas sensing mechanism and the measurement of sensitivity are also explained in this chapter. Seventh chapter describes the fabrication of ITO and AlN gas sensing devices, and response of the devices for various gases. Finally, summary and main conclusion of the research work and some directions for future research that may be carried out are discussed. ACKNOWLEDGEMENT First and Foremost, I thank GOD Almighty for having bestowed me to complete this research work. I am thankful to the Secretary, Bishop Heber College, Tiruchirappalli, and the Principal Dr. D. Paul Dhayabaran, for having granted me permission to do Ph.D. programme in Bishop Heber College, Tiruchirappalli. I am thankful to the Secretary, Sujatha Degree and PG College for Women, Hyderabad, and the Principal Dr. Aruna Singh, for their support in the completion of the thesis. I wish to place on record my heartful thanks to Dr. K. Vijayalakshmi, Assistant Professor, Department of Physics, Bishop Heber College, Tiruchirappalli, for reposing full confidence in my ability to work and write on the subject, for her unceasing and steadfast encouragement and guidance. I wish to gratefully thank her for the care and affection, without which this thesis would not have seen the light of the day. I owe my sincere thanks to Dr. C. Ravidhas, Head, Department of Physics, Bishop Heber College, Tiruchirappalli, for providing laboratory facilities to carry out this research work and for his valuable suggestions and support throughout the course of the programme. My profound thanks to Member of Doctoral Committee, Dr. K.Ramamurthi, Professor, School of Physics, Bharathidasan University, Tiruchirappalli, for his periodic evaluation and candid appraisal of the research work. I wish to express my gratitude to Dr. S. Jayakumar, Head, Department of Physics, PSG College of Technology, Coimbatore, for providing equipments at the thin film laboratory, to carry out this research work. I earnestly thank Dr. A.Chandrabose, Head, Department of Physics, NIT, Tiruchirappalli, for providing laboratory facilities to carry out this research work. Special thanks are extended to Dr. S. Sanjiv Kumar, Scientist, National center for characterization and composition of materials, Hyderabad, for his help in characterization of the samples. I must thank profusely Dr. S. Prasanna, Assistant Professor and E. Nitya, Associate Professor, PSG College of Technology, Coimbatore, for all their help, support, interest and valuable hints. I would like to thank all the Faculty Members of the Department of Physics, Bishop Heber College, Tiruchirappalli, for their encouragement and support during the course of my research work. I am deeply indebted to my parents and my husband for their moral support to complete my research. V. VASANTHIPILLAY LIST OF TABLES Table 1.1 Examples of applications of gas sensor. Table1.2 Types of solid state gas sensors with the corresponding physical change used as gas detection principle. Table 2.1 Mechanical, Thermal and Electrical properties of AlN. Table 4.1 Summary of deposition parameters for ITO thin films. Table 4.2 Deposition rate of ITO thin films for different rf power Table 4.3 Structural parameters of ITO thin films deposited at different rf power Table 4.4 Electrical parameters of ITO thin films deposited at different rf power Table 4.5 Structural parameters of ITO thin films deposited at an rf power of 150 W Table 4.6 Electrical parameters of ITO thin films deposited at an rf power of 150 W Table 5.1 Summary of deposition parameters for AlN thin films Table 5.2 Deposition rate of AlN thin films for different nitrogen concentration Table 5.3 Deposition rate of AlN thin films for different deposition time Table 5.4 Structural parameters of AlN thin films deposited on Si(100) for different deposition time LIST OF FIGURES Figure 1.1 Signal processing in living organisims and in intelligent machines. Figure 1.2 Lennard-Jones model of physisorption and chemisorptions. (a) Physisorption of a molecule (b) Chemisorption of a molecule. Activation energy Ea, dissociation energy Ediss, desorption energy Edes Figure 1.3 Brunauer‘s five types of adsorption isotherms. Figure 1.4 Characteristics of several Langmuir isotherms for different b (T). Figure 2.1 Crystal Structure of Indium tin oxide. Figure 2.2 Two indium sites of ITO. Figure 2.3 Carrier concentrations as function of the tin doping level. Figure 2.4 Energy band diagrams of In2O3 and ITO. Figure 2.5 Crystal structure of the Aluminum Nitride. Figure 2.6 Geometry of crystallographic planes (002), (102) and (101) in Hexagonal AlN lattices. Figure 3.1 Schematic diagram of rotary pump. Figure 3.2 Schematic diagram of a diffusion pump Figure 3.3 Schematic diagram of penning gauge. Figure 3.4 Schematic diagram of vacuum coating unit. Figure 3.5 Photograph of the dc/rf magnetron sputtering unit. Figure 3.6 Photograph of the Rutherford backscattering spectrometer Figure 3.7 The geometry of the incident X-rays impinging the sample satisfies the Bragg Equation. Figure 3.8 Schematic of the detection of diffracted X-rays by diffractometer Figure 3.9 Photograph of the X-ray diffraction unit Figure 3.10 Schematic diagram of Scanning electron microscope Figure 3.11 Photograph of the Scanning electron microscope Figure 3.12 Schematic diagram of FTIR spectrometer system Figure 3.13 Photograph of FTIR spectrometer Figure 3.14 Schematic diagram of UV-VIS spectrophotometer Figure 3.15 Photograph of UV-VIS spectrophotometer Figure 3.16 Photograph of Precision LCR Meter Figure 3.17 Schematic diagram of LCR measurement set up (a) with specimen (b) without specimen Figure 4.1 The dependence of deposition rate of ITO thin films on rf power Figure 4.2 XRD pattern
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