Sains Malaysiana 49(6)(2020): 1461-1470

http://dx.doi.org/10.17576/jsm-2020-4906-24

Komposisi Ikatan Kimia dan Mekanisme Pertumbuhan Filem Nipis a-CN_x oleh Teknik rf-PECVD Suhu Rendah

(Chemical Bonding Composition and Growth Mechanism of a-CN_x Thin Films by Low-Temperature rf-PECVD Technique)

SITI AISYAH ABD AZIZ & ROZIDAWATI AWANG*

Program Fizik, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan

Malaysia

Diserahkan: 4 November 2019/Diterima: 13 Februari 2020

ABSTRAK

Dalam kajian ini, filem nipis karbon nitrida amorfus (a-CN_x) telah dimendapkan menggunakan teknik pemendapan wap kimia secara peningkatan plasma berfrekuensi radio, (radio-frequency plasma enhanced chemical vapor deposition, rf-PECVD). Sampel disediakan pada suhu substrat yang berbeza iaitu pada 80, 100, 120, 150 dan 180 ℃ dan kesannya ke atas morfologi, kadar pemendapan serta komposisi ikatan kimia sampel dikaji. Seterusnya, mekanisme pertumbuhan filem nipis a-CNx daripada campuran gas asetilena (C2H2) dan nitrogen (N2) dicadangkan. Ketebalan filem nipis dan morfologi filem nipis a-CNx diciri menggunakan mikroskop elektron imbasan pancaran medan (field emission scanning electron microscopy, FESEM).Manakala komposisi ikatan kimia diperoleh daripada pencirian menggunakan spektroskopi infra-merah jelmaan Fourier (Fourier transform infrared spectroscopy FTIR).Morfologi filem nipis a-CN_x kelihatan seperti kobis bunga yang padat dan butiran yang seragam. Manakala sampel yang dimendapkan pada suhu 100 dan 180 ℃ menunjukkan struktur butiran bersaiz nano pada keseluruhan permukaan filem. Kadar pemendapan filem nipis a-CN_x maksimum pada suhu pemendapan 120 ℃ dan minimum pada 180 ℃. Secara keseluruhannya, semua sampel menunjukkan kehadiran ikatan C-N, C=C, C=N, C≡N, C-H dan N-H/O-H iaitu ikatan yang berpadanan wujud dalam filem nipis a-CN_x. Dalam kajian ini, mekanisme pertumbuhan filem nipis a-CNx membincangkan pembentukan C-H, C-N dan keluaran sampingan HCN hasil daripada penguraian gas C₂H₂ dan N₂. Pertumbuhan filem a-CN_x juga disebabkan tindak balas kinetik semasa proses pemendapan iaitu penjerapan spesies karbon dan nitrogen pada permukaan pertumbuhan filem dan nyahjerapan spesies nitrida tepu, kesan daripada spesies bertenaga serta mobiliti spesies yang tinggi pada permukaan pertumbuhan. Maka, komposisi ikatan kimia dan kadar pemendapan filem dipengaruhi oleh keseimbangan antara molekul CN dengan atom C dan N mencapai permukaan pertumbuhan filem.

Kata kunci: FTIR; morfologi; saiz nano

ABSTRACT

In this study, amorphous carbon nitride (a-CN_x) thin films were deposited using radio-frequency plasma enhanced chemical vapor deposition (rf-PECVD) technique. Samples were prepared at different substrate temperatures of 80, 100, 120, 150, and 180 ℃ and the effect on morphology, deposition rate and chemical bonding composition were studied. Next, the growth mechanism of a- CN_x thin films using acetylene (C₂H₂) and nitrogen (N₂) as gas precursor. Film thickness and morphology of a-CN_x thin film were characterized using field emission scanning electron microscopy (FESEM), while the chemical bonding composition was obtained using Fourier transform infrared spectroscopy (FTIR). The morphology of the a-CN_x thin film looks like a uniform structural shape of a cauliflower. Whereas samples deposited at 100 and 180 ℃ show nanosize granular structure on the entire surface of the film. Maximum deposition rate of a-CNx thin films at deposition temperature of 120 ℃ and minimum at 180 ℃. Overall, all samples show the presence of C-N, C = C, C = N, C≡N, C-H and N-H /O-H bonds, which are the corresponding bonds present in a-CN_x thin films. In this study, the growth mechanism of a-CN_x thin films discusses the formation of C-H, C-N and HCN by-products resulting from the decomposition of C₂H₂ and N₂ gas. The growth of a- CN_x films was also due to the kinetic reactions during the deposition process: the adsorption of carbon and nitrogen species on the surface of the film growth and the desorption of saturated nitride species, caused by energetic species, and the high mobility of the species on the growth surface. Thus, the chemical bonding composition and deposition rate of the film is influenced by the equilibrium between the CN molecules and the C and N atoms reaching the film growth surface.

Keywords: FTIR; morphology; nano size

RUJUKAN

Alibart, F., Peponas, S., Charvet, S. & Benlahsen, M. 2011. The effect of the terminating bonds on the electronic properties of sputtered carbon nitride thin films. Thin Solid Films 519(10): 3430-3436.

Awang, R., Purhanudin, N. & Salman, N.S. 2018. Effect of radio frequency power on a-CNx film properties and its performance as humidity sensors. Sains Malaysiana 47(11): 2863-2867.

Aziz, N.F.H., Ritikos, R., Kamal, S.A.A., Hussain, N.S.M. & Awang, R. 2013. Effect of N₂ composition ratio and annealing on morphology and optical properties of a-CNx thin films. AIP Conference Proceedings 1571: 125-131.

Aziz, S.A.A. & Awang, R. 2017a. Influence of RF power on chemical bonding composition on a- CNx thin films as humidity sensor. Sains Malaysiana 46(10): 1951-1958.

Aziz, S.A.A., Purhanudin, N. & Awang, R. 2017b. Chemical bonding and humidity sensing properties of amorphous carbon nitride (a-CNx) by acetylene gas. AIP Conference Proceedings 1838: 020010.

Behnisch, J., Holländer, A. & Zimmermann, H. 1993. Surface modification of polyethylene by remote dc discharge plasma treatment. Journal of Applied Polymer Science 49(1): 117-124.

Bousetta, A., Lu, M., Bensaoula, A. & Schultz, A. 1994. Formation of carbon nitride films on Si(100) substrates by electron cyclotron resonance plasma assisted vapor deposition. Applied Physics Letters 65(6): 696-698.

Cometto, O., Dennett, C.A., Tsang, S.H., Short, M.P. & Teo, E.H.T. 2018. A thermal study of amorphous and textured carbon and carbon nitride thin films via transient grating spectroscopy. Carbon 130: 355-361.

Ferrari, A.C., Rodil, S.E. & Robertson, J. 2003. Interpretation of infrared and Raman spectra of amorphous carbon nitrides. Physical Review B 67(15): 155306.

Hammer, P., Baker, M.A., Lenardi, C. & Gissler, W. 1997. Synthesis of carbon nitride films at low temperatures. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 15(1): 107-112.

Hellgren, N., Macák, K., Broitman, E., Johansson, M.P., Hultman, L. & Sundgren, J. 2003. Influence of plasma parameters on the growth and properties of magnetron sputtered CN_x thin films. Journal of Applied Physics 88(1): 524-532.

Hsu, C.Y. & Hong, F.C.N. 1999. The effect of substrate temperature on the growth of CNx films with beta-C₃N₄-like microcrystallites by an inductively coupled plasma (ICP) sputtering method. Diamond and Related Materials 8(7): 1315-1323.

Kaneko, S., Mele, P., Endo, T., Tsuchiya, T., Tanaka, K., Yoshimura, M. & Hui, D. 2017. Electrical properties of amorphous carbon nitride thin films for pressure sensor applications. Carbon-related Materials in Recognition of Nobel Lectures by Prof. Akira Suzuki in ICCE. Berlin: Springer. m.s. 261-275.

Kayed, K. 2019. The optical band gap in amorphous carbon nitride thin films: Effect of sp² hybridized C atoms configurations. Fullerenes Nanotubes and Carbon Nanostructures 27(10): 796-802.

Kayed, K. 2018. Effect of nitrogen plasma afterglow on the surface charge effect resulted during XPS surface analysis of amorphous carbon nitride thin films. Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy 199: 242-247.

Khanis, N.H., Ritikos, R., Othman, M., Abdul Rashid, N.M., Siti, S.M. & Rahman, S.A. 2013. Catalyst free carbon nitride nanostructures prepared by rf-PECVD technique on hydrogenated amorphous carbon template. Materials Chemistry and Physics 138(2-3): 514-518.

Kim, J.H., Ahn, D.H., Kim, Y.H. & Baik, H.K. 1997. Characterization of amorphous hydrogenated carbon nitride films prepared by plasma-enhanced chemical vapor deposition using a helical resonator discharge. Journal of Applied Physics 82(2): 658-665.

Kundoo, S., Chattopadhyay, K.K., Banerjee, A.N. & Nandy, S.K. 2003. Synthesis and optical characterization of amorphous carbon nitride thin films by hot filament assisted RF plasma CVD. Vacuum 69(4): 495-500.

Mao, J., Xiong, Z. & Cao, L. 2018. Synthesis and optical properties in UV-visible range of carbon nitride thin films. Journal of Vacuum Science and Technology 38(5): 369-374.

Purhanudin, N. & Awang, R. 2016. Formation of chemical bonds and morphological studies of a- CNx: Effects of PECVD deposition pressure. AIP Conference Proceedings 1784: 040018.

Ray, S.C., Mbiombi, W. & Papakonstantinou, P. 2014. Electrical and electronic properties of nitrogen doped amorphous carbon (a-CNx) thin films. Current Applied Physics 14(12): 1845- 1848.

Ritikos, R., Siong, C.C., Ab Gani, S.M., Muhamad, M.R. & Rahman, S.A. 2009. Effect of annealing on the optical and chemical bonding properties of hydrogenated amorphous carbon and hydrogenated amorphous carbon nitride thin films. Japanese Journal of Applied Physics 48(10): 101301.

Rodil, S.E., Beyer, W., Robertson, J. & Milne, W.I. 2003. Gas evolution studies for structural characterization of hydrogenated carbon nitride samples. Diamond and Related Materials 12(3-7): 921-926.

Sawahata, J., Teramoto, M., Nakamura, S., Kametomo, K., Satake, M., Yamamoto, S.I., Itoh, K. & Takarabe, K. 2014. Structural and optical properties of boron-doped amorphous carbon nitride thin films synthesized by microwave electron cyclotron resonance-plasma chemical vapor deposition. Japanese Journal of Applied Physics 53(7): 071002.

Sjöström, H., Hultman, L., Sundgren, J.E., Hainsworth, S.V., Page, T.F. & Theunissen, G.S.A.M. 1996. Structural and mechanical properties of carbon nitride CN x (0.2⩽ x ⩽0.35) films. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 14(1): 56-62.

Wright, A.N. & Winkler, C.A. 1968. Active Nitrogen. New York: Academic Press.

Yasuda, H. & Hirotsu, T. 1978. Critical evaluation of conditions of plasma polymerization. Journal of Polymer Science: Polymer Chemistry Edition 16(4): 743-759.

Yasuda, H., Bumgarner, M.O. & Hillman, J.J. 1975. Polymerization of organic compounds in an electrodeless glow discharge. IV. Hydrocarbons in a closed system. Journal of Applied Polymer Science 19(2): 531-543.

Yu, G.Q., Lee, S.H., Lee, D.G., Na, H.D., Park, H.S. & Lee, J.J. 2002. Synthesis and characterization of carbon nitride thin films prepared by rf plasma enhanced chemical vapor deposition. Surface and Coatings Technology 154(1): 68-74.

Zabolotny, E.R. & Gesser, H. 1962. The reaction of active nitrogen with simple hydrocarbons. The Journal of Physical Chemistry 66(5): 854-856.

*Pengarang untuk surat-menyurat; email: rozida@ukm.edu.my