PECVD HYDROGENATED AMORPHOUS CARBON FILMS: GROWTH AND CHARACTERIZATION ROZIDAWATI BINTI AWANG

Transcription

1 PECVD HYDROGENATED AMORPHOUS CARBON FILMS: GROWTH AND CHARACTERIZATION ROZIDAWATI BINTI AWANG SUBMISSION OF RESEARCH THESIS FOR THE FULFILMENT OF THE DEGREE OF DOCTOR OF PHILOSOPHY FACULTY OF SCIENCE JULY 2008

2 DECLARATION I hereby declare that the work reported in this thesis is my own unless specified and duly acknowledged by quotation February (ROZIDAWATI BINTI AWANG) ii

3 ACKNOWLEDGEMENTS In the name of Allah, the Most Gracious, the Most Merciful... First and foremost, I would like to express my most sincere gratitude to my supervisor, Prof. Datin Dr. Saadah Abdul Rahman for her guidance, encouragement and understanding during this research work. My gratitude also goes to the Universiti Kebangsaan Malaysia for giving me full time study leave under SLAB scheme and allowing me to pursue my PhD degree at University of Malaya. The financial supports of this research by the Ministry of Science and Technology under IRPA grant of project No EA222 and University Malaya under Vot F grant No.F0242/2005A are fully acknowledged. I would like to take this opportunity to express my thanks to Prof. Muhammad Mat Salleh, Prof Khalijah and all my lecturers for their useful suggestions and support. My thanks also go to En. Mohamad Aruf, En. Ismail Che Lah and Pn. Norlela for their kind technical assistance in the Solid State Laboratory. I am also thankful to the company of Shin-Etsu Handoutai, Malaysia for the use of Micro- Raman instrument. My thanks also goes to my colleges, Goh, Richard, Anis, Juliana and all members of Physics Department for their assistance and friendship. My special gratitude is due to my husband, Muhamad Zahari for his encouragement, support and love. To my dear son, Aimann, thank you for being understanding when I was not always there during the process of completing this work. Last but not least, I would also thank our parents, Ma, Pa, Mak, Ayah and all family members for their constant encouragement and prayers. iii

4 ABSTRACT This research offers critical insights on the growth and characterization of hydrogenated amorphous carbon (a-c:h) thin films by plasma enhanced chemical vapour deposition (PECVD). The initial phase of this work involved designing and building the reaction chamber for the PECVD system intended for the preparation of a-c:h thin films. The second phase is focused on ensuring that the PECVD system is capable of producing good quality and reproducible a-c:h films. The effects of RF discharge power on the optical and chemical bonding properties of the films are investigated. These results are used to explain the deposition kinetics of the films and to check for consistencies with published results. The third phase was focused on studying the effects of deposition time and film thickness on the optical and chemical bonding properties of the films prepared at high and low RF powers. The study on the influence of hydrogen (H 2 ) and helium (He) dilution of methane (CH 4 ) on the optical and chemical bonding properties of the films deposited by direct current (DC) PECVD is the focus of the fourth phase of this work. The final phase investigates the effects of deposition time and film thickness on the optical and chemical bonding properties of the films deposited by DC PECVD using H 2 or He diluted CH 4. These films are deposited using high and low H 2 /He to CH 4 flow-rate ratios. Optical transmission spectroscopy, Fourier transform infrared (FTIR) spectroscopy and micro-raman scattering spectroscopy are used to study the optical and chemical bonding properties of the films. The results of this work demonstrated that increase in RF discharge power increased the deposition rate and the sp 2 fraction in the films but significantly reduced the optical band gap, E g, H content and sp 2 cluster size. These results were consistent with published results and the variation of the properties of the films with RF power was consistent with the deposition kinetics of the a-c:h films. This confirmed that the home-built PECVD system designed and built for this work was capable of producing good quality and reproducible a-c:h films. E g and sp 2 cluster size were found to be dependent on deposition time and film thickness. These parameters decreased with increase in film thickness. An increase in deposition time resulted with an increase in sp 2 fraction and disorder in the film structure. The sp 2 C content increased and H content in the films decreased with increase in diluent gas (H or He) to CH 4 flow-rate ratio. Long deposition time retarded the growth rate of a-c:h films due to etching effects in films deposited from both H 2 and He diluted methane. Increase in deposition time increased the sp 2 C content in the film structure which consistently led to a decrease in E g. In H 2 diluted methane films, long deposition times allowed longer exposure to the H etching effect resulting in the creation of small sp 2 clusters which reduced bond angle distortion and increased the distribution of cluster sizes. In helium diluted methane films, longer exposure to hydrocarbon ion bombardment has comparatively very small effects on the size and structural disorder in the films. iv

5 ABSTRAK Penyelidikan ini mendalami kaedah pemendapan dan pencirian filem nipis amorfus karbon berhidrogen (a-c:h) daripada teknik pemendapan wap kimia secara peningkatan plasma (PWKPP). Fasa pertama penyelidikan ini adalah merekabentuk ruang tindakbalas dan membina sistem PWKPP untuk menghasilkan sampel-sampel filem a-c:h. Fasa kedua memfokus kepada penentuan keupayaan sistem PWKPP berfungsi untuk menghasilkan filem a-c:h berkualiti tinggi serta keboleh-ulangan penyediaan sampel. Kesan kuasa frekuensi radio (FR) kepada sifat optik dan ikatan kimia filem dikaji. Hasilnya digunakan untuk menerangkan kinetik pemendapan filem dan menyemak kesetaraan hasil yang diperolehi oleh penyelidik-penyelidik lain. Fasa ketiga memfokus kepada kesan masa pemendapan dan ketebalan filem terhadap sifat optik dan ikatan kimia filem yang dihasilkan pada keadaan FR kuasa tinggi dan rendah. Kajian ke atas kesan gas metana (CH 4 ) yang dicampurkan dengan gas hydrogen (H 2 ) atau gas helium (He) kepada sifat optik dan ikatan kimia filem yang dimendapkan daripada PWKPP arus terus (AT) merupakan fokus kajian fasa keempat. Fasa terakhir mengkaji kesan masa pemendapan dan ketebalan filem terhadap sifat optik dan ikatan kimia filem yang dihasilkan oleh PWKPP AT menggunakan gas metana yang dicampurkan dengan gas hidrogen atau gas helium. Filem-filem ini dimendap menggunakan nisbah kadar-aliran H 2 / He kepada CH 4 pada keadaan nisbah tinggi dan rendah. Spektroskopi pemancar optik (UV-Nir-Vis), spektroskopi Transformasi Fourier Inframerah (FTIR) dan spektroskopi-mikro Raman digunakan untuk pencirian sifat optik dan ikatan kimia filem. Hasil penyelidikan ini menunjukkan peningkatan kuasa FR meningkatkan kadar pemendapan dan kandungan sp 2 di dalam filem tetapi menurunkan nilai E g, kandungan H dan saiz kluster sp 2. Hasil ini setara dengan hasil yang telah diterbitkan dan variasi sifat filem dengan kuasa FR adalah setara dengan kinetik pemendapan filem a-c:h. Maka, dapat disahkan bahawa sistem PWKPP yang dibina ini berfungsi dengan baik, menghasilkan filem a-c:h berkualiti tinggi dan penyediaannya bolehulang. Nilai E g dan saiz kluster sp 2 di dapati bergantung kepada masa pemendapan dan ketebalan filem. Parameter ini berkurang apabila ketebalan filem bertambah. Peningkatan masa pemendapan meningkatkan kandungan sp 2 dan ketidaktertiban struktur filem. Kandungan sp 2 bertambah dan kandungan H berkurang bila nisbah kadar-aliran gas campuran (H 2 atau He) terhadap gas CH 4 ditingkatkan. Peningkatan masa pemendapan merencatkan kadar pemendapan filem a-c:h disebabkan kesan pemunaran di dalam filem yang dimendapkan daripada kedua-dua keadaan H 2 atau He dicampurkan dengan gas CH 4. Peningkatan masa pemendapan meningkatan kandungan sp 2 di dalam struktur filem yang menyebabkan penurunan nilai E g. Bagi filem daripada CH 4 yang dicampurkan dengan H 2, pemanjangan masa pemendapan membenarkan lebih pendedahan kepada proses pemunaran yang menyebabkan penghasilan kluster sp 2 bersaiz kecil yang mengurangkan herotan sudut ikatan dan meningkatkan taburan saiz kluster. Bagi filem daripada CH 4 yang dicampurkan dengan He, pemanjangan masa pendedahan kepada proses pemunaran oleh ion hidrokarbon berkelajuan tinggi di dapati hanya memberi kesan yang kecil terhadap saiz kluster dan ketidaktertiban struktur filem. v

6 TABLE OF CONTENTS Declaration... ii Acknowledgement......iii Abstract Abstrak.....iv v Table of contents.. vi List of Figures xii List of Tables...xvii List of Published Papers.. xviii CHAPTER 1: INTRODUCTION 1.1 Introduction Historical background of hydrogenated amorphous carbon (a-c:h) Different forms of carbon Physical properties of hydrogenated amorphous carbon Some applications of a-c:h Focus and Motivation of Research Outline of the thesis.12 CHAPTER 2: LITERATURE REVIEW 2.1 Introduction Deposition Processes of Hydrogenated Amorphous Carbon (a-c:h) Films Ion Beam Deposition Techniques Sputtering Techniques vi

7 2.2.3 Plasma Enhanced Chemical Vapour Deposition (PECVD) Techniques (a) Direct Current Plasma Enhanced Chemical Vapour Deposition (DC PECVD) (b) Radio Frequency Plasma Enhanced Chemical Vapour Deposition (RF PECVD) Growth mechanism in Plasma Enhanced Chemical Vapour Deposition of a-c:h films Plasma kinetics Basic stages of plasma deposition (a) Reactions in the plasma discharge of methane (b) The plasma-surface interaction (c) The sub-surface reactions to form a solid film Reaction on the growing surface of the film Influence of Deposition Parameters in PECVD a-c:h films Effects of Deposition Pressure Effects of Substrate Temperature Effects of Discharge Power Effects of Applied Bias Voltage Effects of Reactive Gases used in Deposition Effects of Dilution of Reactive Gases in Deposition Effects of Film Thickness Optical properties of a-c:h Films Optical band gap of a-c:h films UV-Visible spectroscopy Chemical bonding Properties of a-c:h Films Atomic bonding structure: Hybridization of a-c:h...33 vii

8 2.6.2 Robertson s a-c:h Cluster Model Role of hydrogen in a-c:h films Fourier Transmission Infrared Spectroscopy (FTIR) Raman Spectroscopy.37 CHAPTER 3: EXPERIMENTAL AND ANALYTICAL TECHNIQUES 3.1 Introduction Deposition Technique Plasma Enhanced Chemical Vapour Deposition (PECVD) System (a) The Reaction Chamber (b) The Gas Distribution Subsystem (c) The Electrical Subsystem (d) The Evacuation Subsystem Operation Preparation Procedures of Hydrogenated Amorphous Carbon (a-c:h) Thin Films (a) Substrate Cleaning Procedures (b) Pre-Deposition Process (c) Deposition Process (d) Post-Deposition Process Analytical Techniques Ultraviolet/Visible/Near Infrared (UV/Vis/Nir) Spectroscopy (a) Measurement Procedures (b) Transmission Spectrum with Interference Fringes (c) Transmission Spectrum without Interference Fringes (d) The Tauc Plot: Optical Band Gap and Structural Order. 64 viii

9 3.3.2 Fourier Transform Infrared (FTIR) Spectroscopy Measurement (a) Measurement Procedures (b) Determination of Hydrogen Content 3.3.2(c) Determination of sp 2 Carbon Content Raman Scattering Spectroscopy (a) Measurement Procedures (b) Analysis of Raman Spectra of a-c:h Films: D and G Band (c) Determination of sp 2 Cluster Size.71 CHAPTER 4: RF PECVD a-c:h FILMS FROM PURE METHANE: RESULTS, ANALYSIS AND DISCUSSIONS 4.1 Introduction Preparation Condition of RF PECVD a-c:h films from Pure Methane Optical Transmission Spectroscopy Measurements: Results and Analysis Optical Transmission Spectra of RF PECVD a-c:h Films Prepared from Pure Methane Deposition rate Optical band gap Infrared Transmission Spectroscopy Measurements: Results and Analysis FTIR Spectra of RF PECVD a-c:h Films Prepared from Pure Methane Hydrogen and sp 2 Carbon Content Raman Spectra of a-c:h films: Results and Analysis...96 ix

10 4.5.1 Raman Spectra of RF PECVD a-c:h Films Prepared from Pure Methane Disorder and sp 2 Carbon Clusters Summary CHAPTER 5: DC PECVD a-c:h FILMS FROM HYDROGEN AND HELIUM DILUTED METHANE: RESULTS, ANALYSIS AND DISCUSSIONS 5.1 Introduction Preparation Condition of Methane Diluted a-c:h films Optical Transmission Spectroscopy Measurement: Results and Analysis Optical Transmission Spectra of DC PECVD a-c:h Films Prepared from Hydrogen Diluted Methane Optical Transmission Spectra of DC PECVD a-c:h Films Prepared from Helium Diluted Methane Deposition rate Optical band gap, E g (a) Effects of H:CH 4 and He:CH 4 flow rate ratio (b) Effects of deposition time Infra-red Transmission Spectra of DC PECVD a-c:h films: Results and Analysis FTIR spectra of DC PECVD a-c:h Films Prepared from diluted Methane Hydrogen content and sp 2 carbon content (a) Effects of H:CH 4 and He:CH 4 flow rate ratio (b) Effects of deposition time Raman Spectra of a-c:h films: Results and Analysis x

11 5.5.1 Raman Spectra of DC PECVD a-c:h Films from Hydrogen diluted Methane Raman Spectra of DC PECVD a-c:h Films from Helium diluted Methane Disorder and sp 2 Carbon Clusters (a) Effects of H:CH 4 and He:CH 4 flow rate ratio (b) Effects of deposition time Summary CHAPTER 6: CONCLUSIONS AND SUGGESTIONS FOR FURTHER WORK 6.1 Conclusions Suggestions for Further Work Concluding Remarks REFERENCES APPENDIX A APPENDIX B APPENDIX C xi

12 LIST OF FIGURES Figure 1.1 Figure 2.1 Figure 2.2 Figure 2.3 Figure 2.4 Figure 2.5 Figure 2.6 Figure 2.7 The three bond hybridizations found in carbon Glowing/Luminous zone and dark spaces in DC glow discharge The voltage distribution in DC glow discharge Schematic representation of amorphous semiconductors absorption spectrum Schematic density of states (DOS) of a carbon showing σ and π states A typical infrared transmission curve of a-c:h films obtained by FTIR spectrometer G and D modes Schematic variation of the Raman G peak position and I(D)/I(G) during the three stages of amorphisation Figure 3.1(a) Photograph of the home-built PECVD deposition system Figure 3.1(b) Schematic diagram of PECVD deposition system Figure 3.2(a) Photograph of the home-built reaction chamber for the PECVD system Figure 3.2(b) Schematic diagram of the home-built reaction chamber for the PECVD system Figure 3.3 Figure 3.4 Figure 3.5 Figure 3.6 Figure 3.7 Stainless steel masks (top view) Block diagram of the optical transmission setup A typical optical transmission spectrum of a-c:h film Transmission with envelope function of T max and T min Reflection, transmission and absorption of light by an a-c:h thin film sample Figure 3.8 An example of a curve fitting plot using MATLAB 7.0 Figure 3.9 Figure 3.10 Figure 3.11 A typical plot of (αe ) ½ versus E Determination of E 04 optical gap Renishaw System 2000 Raman Spectrometer xii

13 Figure 3.12 Figure 4.1 Figure 4.2 Figure 4.3 A typical Raman spectrum from an a-c:h film The optical transmission spectra of RF PECVD a-c:h films obtained from pure methane gas prepared at different RF power of 15 W The optical transmission spectra of RF PECVD a-c:h films obtained from pure methane gas, RF power of 15 W, deposited at different deposition time The optical transmission spectra of RF PECVD a-c:h films obtained from pure methane gas, RF power of 50 W, deposited at different deposition time Figure 4.4(a) Variation of deposition rates of RF PECVD a-c:h films prepared from pure methane gas at different discharge power Figure 4.4(b) W 1/2 dependence of deposition rates. Figure 4.5 Figure 4.6 Figure 4.7 Figure 4.8 Figure 4.9 Figure 4.10 Variation of deposition rates of RF PECVD a-c:h films prepared from pure methane gas with deposition time at RF power of 15 W and 50 W Variation of Tauc band gap of RF PECVD a-c:h films prepared from pure methane gas at different discharge power Variation of Tauc band gap of a-c:h films prepared from pure methane gas with film thickness at RF powers of 15 W and 50 W Normalized absorption coefficient spectra of the C-H stretching vibrational bands at wavenumber of 2900cm -1 prepared by RF PECVD technique at (a) different power (b) the power of 15 W with different deposition time and (c) at the power of 50W with different deposition time Variation of hydrogen content of RF PECVD a-c:h films prepared from pure methane gas at different discharge power Dependence of sp 2 carbon content in RF PECVD a-c:h films prepared from pure methane gas on discharge power Figure 4.11 Variation of hydrogen content with film thickness in RF PECVD a- C:H films prepared from pure methane gas at RF power of 15 W and 50 W Figure 4.12 Variation of sp 2 carbon content with film thickness in RF PECVD a- C:H films prepared from pure methane gas at RF powers of 15 W and 50 W xiii

14 Figure 4.13 Raman spectra of a-c:h films prepared by RF PECVD from pure methane discharge (a) at different powers (b) at RF power of 15 W with different deposition times and (c) at RF power of 50W with different deposition times Figure 4.14(a) Variation of the G peak position of RF PECVD a-c:h films prepared from pure methane gas with RF discharge power Figure 4.14(b) Variation the FWHM of the D band of RF PECVD a-c:h films prepared from pure methane gas with discharge power Figure 4.14(c) Variation of intensity ratio I (D) /I (G) of RF PECVD a-c:h films prepared from pure methane gas at different discharge power Figure 4.14(d) Variation of cluster size of RF PECVD a-c:h films prepared from pure methane gas at different discharge power Figure 4.15(a) Variation of G peak position of RF PECVD a-c:h films prepared from pure methane gas with film thickness at RF power of 15 W and 50 Figure 4.15(b) Variation of FWHM of D band of RF PECVD a-c:h films prepared from pure methane gas with film thickness at RF power of 15 W and 50 Figure 4.15(c) Variation of intensity ratio I(D)/I(G) of RF PECVD a-c:h films prepared from pure methane gas with film thickness at RF power of 15 W and 50 Figure 4.15(d) Variation of cluster size of RF PECVD a-c:h films prepared from pure methane gas with film thickness at RF power of 15 W and 50 Figure 5.1 The optical transmission spectra of DC PECVD hydrogen diluted a- C:H films prepared at methane to hydrogen flow rate ratio of 1:1 (MH20), 1:2 (MH40), 1:3 (MH60), 1:4 (MH80) and 1:5 (MH100) Figure 5.2 The optical transmission spectra of DC PECVD hydrogen diluted a- C:H films prepared at fixed hydrogen to methane ratio of (2:1), with a deposition time of 1 hour (MH40-1), 2 hours (MH40-2), 3 hours (MH40-3), 4 hours (MH40-4) and 5 hours (MH40-5) Figure 5.3 The optical transmission spectra of DC PECVD hydrogen diluted a- C:H films prepared at fixed hydrogen to methane ratio of (5:1), with a deposition time of 1 hour (MH100-1), 2 hours (MH100-2), 3 hours (MH100-3), 4 hours (MH100-4) and 5 hours (MH100-5) Figure 5.4 The optical transmission spectra of DC PECVD helium diluted a-c:h films prepared at methane to helium flow rate ratio of 1:1 (MHe20), 1:2 (MHe40), 1:3 (MHe60), 1:4 (MHe80) and 1:5 (MHe100) xiv

15 Figure 5.5 Figure 5.6 Figure 5.7 Figure 5.8 Figure 5.9 Figure 5.10 Figure 5.11 Figure 5.12 The optical transmission spectra of DC PECVD helium diluted a-c:h films prepared at fixed helium to methane ratio of (1:1), with a deposition time of 1 hour (MHe20-1), 2 hours (MHe20-2), 3 hours (MHe20-3), 4 hours (MHe20-4) and 5 hours (MHe20-5) The optical transmission spectra of DC PECVD helium diluted a-c:h films prepared at fixed helium to methane ratio of (5:1), with a deposition time of 1 hour (MHe100-1), 2 hours (MHe100-2), 3 hours (MHe100-3), 4 hours (MHe100-4) and 5 hours (MHe100-5) Deposition rate variation with diluents gas to CH 4 flow-rate ratio for DC PECVD a-c:h films Deposition rate variation of DC PECVD a-c:h films from hydrogen and helium diluted methane gas prepared at different deposition time and a flow-rate ratio of 5:1. Deposition rate variation of DC PECVD a-c:h films prepared from hydrogen diluted methane gas at different deposition time and a flowrate ratio of 2:1 and 5:1 Deposition rate variation of DC PECVD a-c:h films from helium diluted methane gas prepared at different deposition time and a flowrate ratio of 1:1 and 5:1 Band gap variation of DC PECVD a-c:h films obtained from hydrogen and helium diluted methane gas prepared at different flowrate ratio. Energy gap variation of DC PECVD a-c:h films prepared from hydrogen and helium diluted methane gas with deposition time for diluent gas to CH 4 flow-rate ratio of 5:1. Figure 5.13 Normalized absorption coefficient spectra of C-H stretching vibrational bands at wavenumber 2900cm -1 prepared by hydrogen diluted methane at (a) H:CH 4 flow rate ratio of 1:1 (MH20), 1:2 (MH40), 1:3 (MH60), 1:4 (MH80) and 1:5 (MH100), (b) 2:1 flow rate ratio with deposition time of 1 hour (MH40-1), 2 hours (MH40-2), 3 hours (MH40-3), 4 hours (MH40-4) and 5 hours (MH40-5), and (c) 5:1 flow rate ratio with deposition time of 1 hour (MH100-1), 2 hours (MH100-2), 3 hours (MH100-3), 4 hours (MH100-4) and 5 hours (MH100-5). xv

16 Figure 5.14 Figure 5.15 Figure 5.16 Normalized absorption coefficient spectra of C-H stretching vibrational bands at wavenumber 2900cm -1 prepared by helium diluted methane at (a) He:CH 4 flow rate ratio of 1:1 (MHe20), 1:2 (MHe40), 1:3 (MHe60), 1:4 (MHe80) and 1:5 (MHe100), (b) 1:1 flow rate ratio with deposition time of 1 hour (MHe20-1), 2 hours (MHe20-2), 3 hours (MHe20-3), 4 hours (MHe20-4) and 5 hours (MHe20-5), and (c) 5:1 flow rate ratio with deposition time of 1 hour (MHe100-1), 2 hours (MHe100-2), 3 hours (MHe100-3), 4 hours (MHe100-4) and 5 hours (MHe100-5) Typical decomposition of partial IR absorption spectra for a-c:h film centered at 2920 cm -1 (sample in the present study of MHe(20-1). Hydrogen content variation of DC PECVD a-c:h films prepared from hydrogen and helium diluted methane gas at different flow-rate ratio Figure 5.17 sp 2 carbon content variation with flow-rate ratio for DC PECVD a- C:H films deposited from hydrogen and helium diluted methane gas Figure 5.18 Figure 5.19 Figure 5.20 Figure 5.21 Figure 5.22 sp 2 C content variation with deposition time for DC PECVD a-c:h films from hydrogen and helium diluted methane gas at flow-rate ratio of 5:1. A typical Raman spectrum (514.5 nm excitation) from an a-c:h film showing prominent G band (1580 cm -1 ) and smaller shoulder (1350 cm -1 ) due to the D band. The experimental spectrum with overlapping fitted curves is shown. Raman spectra of a-c:h films prepared by hydrogen diluted methane at (a) varied H:CH 4 flow rate ratio of 1:1 (MH20), 1:2 (MH40), 1:3 (MH60), 1:4 (MH80) and 1:5 (MH100), (b) 2:1 flow rate ratio with varied deposition time of 1 hour (MH40-1), 2 hours (MH40-2), 3 hours (MH40-3), 4 hours (MH40-4) and 5 hours (MH40-5), and (c) 5:1 flow rate ratio with varied deposition time of 1 hour (MH100-1), 2 hours (MH100-2), 3 hours (MH100-3), 4 hours (MH100-4) and 5 hours (MH100-5). Raman spectra of a-c:h films prepared by helium diluted methane at (a) varied He:CH 4 flow rate ratio of 1:1 (MHe20), 1:2 (MHe40), 1:3 (MHe60), 1:4 (MHe80) and 1:5 (MHe100), (b) 1:1 flow rate ratio with varied deposition time of 1 hour (MHe20-1), 2 hours (MHe20-2), 3 hours (MHe20-3), 4 hours (MHe20-4) and 5 hours (MHe20-5), and (c) 5:1 flow rate ratio with varied deposition time of 1 hour (MHe100-1), 2 hours (MHe100-2), 3 hours (MHe100-3), 4 hours (MHe100-4) and 5 hours (MHe100-5). Plots of G peak position, FWHM of G band, I (D)/ I (G) integrated intensity ratio, FWHM of D band and sp 2 C cluster size of DC PECVD a-c:h films at different hydrogen/ helium to methane flowrate ratios. xvi

17 Figure 5.23 Variation of G peak position, FWHM of G band, I (D)/ I (G) integrated intensity ratio, FWHM of D band and sp 2 C cluster size of a-c:h films with deposition time. The diluents gas (H 2 or He) to methane flow-rate ratio is fixed at 5:1. xvii

18 LIST OF TABLES Table 1.1 Table 2.1 Table 3.1 Table 3.2 Table 3.3 Table 4.1 Table 4.2 Table 5.1 Table 5.2 Table 5.3 Table 5.4 Properties of various forms of carbon Classification of thin film deposition technologies Fit option of MATLAB Curve Fitting Tool Assignment of IR vibrational frequencies in a-c:h The measurement parameters of micro-raman spectrometer model Renishaw system 2000 The parameters obtained from the optical transmission spectra of the a-c:h films prepared by RF PECVD technique from pure methane The assignments of IR vibrational frequencies of RF PECVD a-c:h films from pure methane gas The ionization current, the direct-current voltage applied across the electrodes and the power maintained during the deposition of films studied in this work The parameters obtained from the optical transmission spectra of the a-c:h films prepared by DC PECVD technique from diluted methane The assignments of IR vibrational frequencies of DC PECVD a-c:h films from hydrogen diluted methane The assignments of IR vibrational frequencies of DC PECVD a-c:h films from helium diluted methane xviii

19 LIST OF PUBLISHED PAPERS 1. Rozidawati Awang, Goh Boon Tong, Siti Meriam Ab. Gani, Richard Ritikos and Saadah A. Rahman, The Effects of Deposition Pressure on the Optical and Structural Properties of d.c. PECVD Hydrogenated Amorphous Carbon Films, Materials Science Forum, Vols. 517 (June 2006), Rozidawati Awang and Saadah A. Rahman, Effects of Helium and Hydrogen dilution on the Optical Properties of D.C. PECVD Hydrogenated Amorphous Carbon Films, Journal of Solid State Science and Technology Letters, Vol. 14, No 2 (2007), Rozidawati Awang and Saadah A. Rahman, Influence of film thickness on the properties of RF PECVD Hydrogenated Amorphous Carbon Films, CP 909, Solid State Science and Technology ICSSST 2006, American Institut of Physics, (2007), p AIP Conference Proceedings 909, pp Richard Ritikos, Goh Boon Tong, Rozidawati Awang, Siti Meriam Abdul Gani and Saadah Abdul Rahman, Dependence of radio frequency power on optical, chemical bonding and photoluminescence properties of hydrogenated amorphous carbon nitride films, IEEE International Conference on Semiconductor Electronics, Proceedings, ICSE, art. no , pp Rozidawati Awang and Saadah A. Rahman The Effects of Hydrogen and Helium dilution on the optical band gap and photoluminescence of DC PECVD Hydrogenated Amorphous Carbon Films, Sains Malaysiana, 37(3): Rozidawati Awang and Saadah A. Rahman, Properties of a-c:h films deposited in CH 4 -H 2 and CH 4 -He D.C Plasma International Journal of Nanoscience, Ms. No. IJN-D Conference Presentations: 1. Rozidawati Awang, Goh Boon Tong, Siti Meriam Ab. Gani, Richard Ritikos and Saadah A. Rahman, Properties of d.c. PECVD Hydrogenated Amorphous Carbon Films, presented (oral) at the Regional Conference on Solid State Science and Technology 2005, December 2005, Kuantan, Pahang, Malaysia. xix

20 2. Rozidawati Awang and Saadah A. Rahman, Influence of Layer Thickness on the Structural Properties of RF PECVD Hydrogenated Amorphous Carbon Thin Films, presented (poster) at the International Conference on Advancedment of Materials and Nanotechnology ( ICAMN 2007), 29 May-1 June 2007, The City Bayview Hotel, Langkawi, Kedah, Malaysia. 3. Rozidawati Awang and Saadah A. Rahman, The Effects of Hydrogen and Helium dilution on the optical band gap and photoluminescence of DC PECVD Hydrogenated Amorphous Carbon Films, presented (oral) at the International Workshop and Conference on Nanotechnology (IWCN 2007), June 2007, Equatorial Hotel, Bangi, Selangor, Malaysia. 4. Rozidawati Awang and Saadah A. Rahman, The effects of helium dilution on the photoluminescence and optical energy gap of Hydrogenated Amorphous Carbon Films, presented (poster) at the 23 rd Regional Conference on Solid State Science and Technology 2007, November 2007, Hyatt Hotel, Johor Bharu, Malaysia. 5. Rozidawati Awang and Saadah A. Rahman, The Effects of hydrogen Dilution on the Photoluminescence and Optical Energy Gap of Hydrogenated Amorphous Carbon Films, presented (poster) at the Nanostructured Advanced Materials, November 2008, University of Jordan, Amman, Jordan. 6. Rozidawati Awang and Saadah A. Rahman, Influence of Film Thickness on Properties of a-c:h Films by RF PECVD, presented (oral) at the IUMRS- ICA2008, 9-13 December 2008, Nagoya Congress Centre, Nagoya, Japan. 7. Aniszawati Azis, Rozidawati Awang and Saadah A. Rahman, Influence of CH4 to SiH4 gas pressure ratio on DC-PECVD a-si:h thin films, presented (oral) at the International Meeting on Frontier of Physics (IMFP 05), July 2005, Kuala Lumpur, Malaysia. xx