S. T. Lin

Growth of highly transparent nanocrystalline diamond films and a spectroscopic study of the growth

A series of nanocrystalline diamond films with grain size ranged from 4 nm to a few hundreds of nanometers were grown by microwave plasma enhanced chemical vapor deposition. Effects of the substrate pretreatment and the methane fraction in the source gas on the microstructure, surface roughness, and optical transmittance of the resultant films were studied. Specifically, comparison was made between two different sizes, 4 nm and 0.1 μm, of the diamond powder used for substrate pretreatment. Interestingly, the films grown on substrates scratched with coarser powder (0.1 μm) can be smoother and more transparent than those on substrates scratched with finer powder (4 nm), despite of the similarity in the grain size of these two types of films prepared at high methane fractions. It is also demonstrated that the major factor that controls the optical transparency is the surface roughness irrespective of the grain size as long as the sp2-bonded carbon in the film is avoided. In situ optical emission spectroscopy...

Mechanical properties of nanocrystalline diamond films

Nanocrystalline diamond (NCD) films with thicknesses in the range of 0.12–1.5μm were deposited on silicon substrates in CH4∕H2∕O2 gas mixtures by microwave plasma-enhanced chemical vapor deposition. The morphology and structure of these NCD films were analyzed by field-emission scanning electron microscopy, x-ray diffraction (XRD), and ultraviolet-Raman spectroscopy. The lower limit of the grain size in the NCD films was estimated to be 10nm from the XRD measurements. These grains are embedded in a columnar-type structure. The elastic and mechanical properties of the NCD films were determined by measuring the dispersion of laser-induced surface acoustic waves. The densities were in the range of 3.41±0.11g∕cm3 and Young’s moduli varied between 674±34 and 953±48GPa, depending on the growth time and deposition conditions. It is concluded that oxygen may have a significant positive effect on the elastic properties of NCD films. The growth rate decreases sharply for an oxygen content in the source gas in exces...

Electronic and bonding structures of B-C-N thin films investigated by x-ray absorption and photoemission spectroscopy

X-ray absorption near-edge structure (XANES) and valence-band photoelectron spectroscopy (PES) were used to investigate the electronic and bonding structures of B-C-N thin films. The intensities of the sp2-bonded features in the C K-edge XANES spectra are found to generally decrease as the C concentration increases, whereas the intensities of the sp2-bonded features in the spectra of N K-edge XANES increase with the N concentration. The decrease of the intensities of the sp2-bonded features in the C and N K-edges XANES spectra correlates with the increase of the C/B and N/B concentration ratios and the increase of Young’s modulus. Valence-band PES spectra are found to be insensitive to the variations of the B and C concentrations in B-C-N compounds

Highly transparent nano-crystalline diamond films via substrate pretreatment and methane fraction optimization

Abstract We report here the growth of highly transparent nano-crystalline diamond films on quartz substrates by microwave plasma enhanced CVD. The effects of methane fraction in the source gas, substrate temperature and substrate pretreatment on the structural and optical properties of these films were studied. Optical transmission spectra, Raman spectra, surface profile as well as X-ray and transmission electron diffraction have been employed to characterize the resultant films. Variations in optical transmittance and in surface roughness as a function of methane fraction exhibited different trend for films grown with different substrate pretreatment. Specifically, comparison was made for two different grain sizes, 4 nm and 0.1 μm, of the diamond powder used for substrate pretreatment. It was demonstrated that the major factor that controls the optical transmittance is the surface roughness provided that the sp 2 -bonded graphitic carbon in the film is avoided. Under optimized conditions, optical transmittance of greater than 84% beyond 700 nm has been obtained for films as thick as 1 μm. Such high optical transparency of these films is primarily attributed to the high smoothness of their surface (average roughness of about 60–65 A) as well as the high content of sp 3 bonded carbon therein.

Mechanical properties of amorphous boron carbon nitride films produced by dual gun sputtering

Mechanical properties and bonding characterisation of amorphous boron carbon nitride (a-BC N ) films prepared by dual gun xy sputtering system was studied. The a-BC N films deposited at different temperatures and having different carbon concentrations xy revealed that at lower deposition temperatures ((200 8C), carbon contents in the range of ;25 at.% produced the harder films where the hardness and elasticmodulus were found to be 12.5 and ;150 GPa, respectively. For higher deposition temperatures (0400 8C), carbon content in the range of 40 at.% produced the harder films. The chemical composition and phase identification were done collectively by X-ray photoelectron spectroscopy and Auger electron spectroscopy. Fourier transform infrared spectroscopy was used to analyse the hybridisation levels of the constituent elements and to show the evolution of different phases in the a-BC N network. The low hardness levels were attributed to the unfavourable C(sp)–N bonding configuration in xy the network, a possible phase separation and high oxygen contents (;10 at.%) in the film. 2003 Elsevier Science B.V. All rights reserved.

Bonding characterization, density measurement, and thermal diffusivity studies of amorphous silicon carbon nitride and boron carbon nitride thin films

Thermal diffusivity (α) of amorphous silicon carbon nitride (a-SiCxNy) and boron carbon nitride (a-BCxNy) thin films on crystalline silicon has been studied as a function of the carbon content and thickness of the films using the traveling wave technique. The thermal diffusivity showed a steady fall from ∼0.35 to about 0.15 cm2/s for a-SiCxNy films as the carbon content increased from 30 to ∼70 at. %. This decrease in thermal diffusivity was also accompanied by a decrease in the film density from 3.35 to ∼2.3 g/cm3 as a function of the carbon content of the a-SiCxNy films. In case of a-BCxNy, a peak in thermal diffusivity (0.6 cm2/s) was detected at a carbon concentration of ∼25 at. % which reduced to 0.2 cm2/s for a carbon concentration of ∼60 at. % in the films. The value of the density also showed a peak (∼2 g/cm3) at a carbon concentration of 25 at. % before decreasing in the a-BCxNy films. A study of bonding characterization revealed a dominant lower coordinated C(sp)–N phase at higher carbon concent...

Bonding characterization and nano-indentation study of the amorphous SiCxNy films with and without hydrogen incorporation

Abstract The hardness and effective modulus of hydrogen-containing and hydrogen-free amorphous SiC x N y films were studied by nano-indentation. Amorphous SiC x N y films with and without hydrogen were deposited by electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) using a SiH 4 –CH 3 NH 2 –N 2 –H 2 gas mixture and hydrogen-free ion-beam sputtering deposition (IBSD), respectively. Fourier-transform infrared spectroscopy (FTIR) studies were used to investigate the bonding states of the SiC x N y materials. SiH, CH and NH bonds were detected by FTIR in ECR-CVD, but not in IBSD, films. The incorporation of hydrogen led to a reduction in both the hardness and modulus of the amorphous SiC x N y films. From nano-indentation measurements, the hardness and effective modulus of the IBSD coated, hydrogen-free amorphous SiC x N y films were 27–30 and 211–258 GPa, respectively. The corresponding values for the ECR-CVD coated, hydrogen-containing amorphous SiC x N y were 22–26 and 115–144 GPa, respectively.

Effect of carbon sources on silicon carbon nitride films growth in an electron cyclotron resonance plasma chemical vapor deposition reactor

Abstract The effect of carbon source on SiCN film growth was studied in an electron cyclotron resonance plasma chemical vapor deposition reactor. The growth characteristics of CH4, C2H2 and CH3NH2 were examined with and without H2 addition during growth. The results indicated that SiCN films were deposited successfully using CH4 with H2 addition as well as using CH3NH2 both with and without H2 addition. (Si; C) and N composition ratios of the films thus deposited were around 0.75. Carbon was hardly incorporated into the films when deposited using C2H2 as the source gas regardless of H2 addition during growth. Among the three source gas studied, CH3NH2 was the most effective for the SiCN films growth. Spectroscopic study of the gas phase species during growth and discussion on the growth phenomena are presented in this paper.

Phase and thickness dependence of thermal diffusivity in a-SiCxNy and a-BCxNy

Thermal diffusivity (α) and bonding configuration of amorphous silicon carbon nitride (a-SiCxNy) and boron carbon nitride (a-BCxNy) films on silicon substrates were studied. Measurement of α by the traveling wave technique and bonding characterisation through X-ray photoelectron spectroscopy in a-SiCxNy and a-BCxNy films having different carbon concentrations revealed that lower coordinated bonds were detrimental to the thermal diffusivity of these films. Furthermore, α was found to depend on the thickness of these films deposited on silicon. This was attributed to the interface thermal resistance between two thermally different materials, the film and the substrate, although other factors such as film microstructure could also play a role. An empirical relation for the variation of thermal diffusivity with thickness is proposed.