Preparation and Characterization of Carbon Nitride Thin Films by Electron Cyclotron Resonance (ECR) Sputtering Method
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Mat. Res. Soc. Symp. Proc. Vol. 555 ©1999 Materials Research Society
The deposited films were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction (XRD). RESULTS AND DISCUSSION Carbon and nitrogen content in the deposited films were determined by XPS analysis. The atomic ratio of nitrogen to carbon (N/C) of the deposited films was varied with substrate self-bias potential. Figure 1 shows N/C atomic ratio of the films deposited at ambient temperature as a
1.4 1.2 1.0
S0.8 Z
0.6 function of substrate self-bias potential. "The N/C ratio of the films increased to a 0.4 maximum point with decreasing the 0.2 substrate self-bias potential and then decreased rapidly. For the film deposited at ambient temperature, the -30 -40 -50 -70 -60 maximum point of N/C ratio was ca. 1.4 Substrate self-bias potential / V and it was observed at around -54 V. The substrate self-bias potential at Fig. I. Relationship between N/C atomic ratio of the maximum N/C ratio was shifted to deposited films and substrate self-bias potential. higher self-bias potential side with Films were deposited at ambient temperature. increasing substrate temperature. When the substrate temperatures were 600 and 700 'C, maximum N/C ratios were observed at around -50 and -45 V, respectively, and maximum N/C ratio ambie nt temp. were ca. 0.9 and ca. 0.93, respectively. sub. p'ot. -51 V .6 The bonding states of nitrogen atoms in the deposited films were investigated by XPS. Figure 2 shows "600 °C C Nis electron spectra of the films C) sub. pot. -50 V C deposited at ambient temperature and at I I I• ' -I 600 'C. N Is binding energy of the film deposited at ambient temperature was 410 405 400 395 390 385 380 398.0 eV and that deposited at 600 'C Binding energy / eV was 400.3 eV. The shift of these electron spectra indicates different Fig. 2. N Is electron spectra of the films deposited at binding states of nitrogen in the ambient temperature and at 600 'C. Substrate selfdeposited films. From the XPS spectra bias potential were -50 V. of organic molecules, N ls binding energy of poly(vinylpyridine), nitrogen bonds to two carbon, is around 399 eV [17], and that of poly(9-vinylcarbazole), in which nitrogen bonds to carbon having sp3 characteristics, is around 400.2 eV [17]. Y. Taki et. al. reported the NIs electron spectra of carbon nitride films prepared by shielded arc ion plating [18]. They reported that Nis spectra have two components, higher I I
,,
J
|
I
energy side component is attributed to aniline-like C-N bonds and lower energy side component
is attributed to pyridine-like C-N bonds. Furthermore, they suggested that component of
420
tetrahedral C-N bond appears at higher energy side, 400.3 eV [18]. From these interpretations,3 we considered that nitrogen in the film deposited at 600 'C bonds to carbon having sp characteristics. Typical Raman spectra of the films deposited at ambient temperature and at 600 'C are shown in Fig. 3. The Raman spectrum of the film deposited at ambient temperature showed a t
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