J.Q Xie

Simulation study on Si and Ge film growth by cluster deposition

Abstract Si and Ge thin film growth from cluster beams has been investigated with molecular-dynamics simulations utilizing the Stillinger–Weber (SW) two- and three-body interaction potentials. The spreading of cluster atoms and the structure of grown films have been studied as a function of incident cluster velocity. We found that higher surface diffusion and spreading of the deposited clusters, which were achieved with a moderate cluster velocity, are necessary for the epitaxial film. However, a very high cluster velocity leads to the damage of the substrate and the growing films. The substrate temperature also plays an important role in the growth of the films.

Carbon nitride films synthesized by the reactive ionized cluster beam technique

Carbon nitride thin films were deposited by the reactive ionized cluster beam (RICB) technique. Fourier transform infrared (FTIR) transmission analysis shows that no marked IR peak exists for the film deposited without nitrogen, whereas a broad peak in the range 1000- and a peak due to the C3pt- 1pt- -1pt-N triple bonds are present for the films deposited with nitrogen. Both FTIR and Raman measurements obviously suggest that C1pt-N single bonds exist when nitrogen is introduced. The intensity of this band rises with increasing nitrogen pressure. The above results are also supported by x-ray photoelectron spectroscopy (XPS) analysis.

RAMAN CHARACTERISTICS OF HARD CARBON-NITRIDE FILMS DEPOSITED BY REACTIVE IONIZED CLUSTER BEAM TECHNIQUES

Abstract Raman spectroscopy was used to investigate the effect of nitrogen pressure on the structure of carbon-nitride films deposited by the reactive ionized cluster beam (RICB) technique. It is noted that a peak centered at about 1248 cm −1 emerges in the Raman spectra and becomes more pronounced when nitrogen pressure is increased. This peak can be attributed to the covalent N C single bonds. Moreover, the structure of the deposited films changes from DLC to diamond, and finally to carbon-nitride with the increase of nitrogen pressure. The results of Knoop hardness tests show the films have rather high hardness up to 6200 kg f/mm 2 .

Molecular-dynamics simulation of low-temperature growth of silicon films by cluster deposition

Silicon thin-film growth from cluster beams at a substrate temperature of 300 K has been investigated with molecular-dynamics simulations utilizing the Stillinger-Weber two- and three-body interaction potential. The spreading of Si-atom clusters and the structure of grown films have been studied as a function of the incident cluster velocity. Our simulation results show that the films grown at a low substrate temperature of 300 K are amorphous and the substrates suffer heavier damage with an increase in the cluster velocity. As compared with our previous results on Si thin-film growth at a substrate temperature of 1000 K, we found that substrate temperature and cluster velocity had a significant impact in determining the structure of the grown films and the cluster spreading on the substrate.

Structure and tribological properties of carbon nitride films obtained by the reactive ionized cluster beam method

Abstract Carbon nitride thin films were synthesized by the reactive ionized cluster beam (RICB) deposition. Raman scattering analysis shows the existence of a characteristic peak due to covalent CN single bonds. This is consistent with the results of Fourier transform infrared (FTIR) transmission measurements. Rutherford backscattering (RBS) measurements show that the composition ratio, N/C, as high as 0.67, can be obtained. The films deposited under the optimized experimental conditions exhibit an extremely high hardness of 61 GPa. The friction and wear behavior of these films without any lubrication were measured by a reciprocating-motion ball-on-disk tribometer. It is noted that the deposited films have low initial and a steady-state friction coefficients less than 0.08. The wear factor of carbon nitride films is significantly lower than that of carbon thin films prepared by the same deposition system and evaluated under similar test conditions. These results are very encouraging for the tribological applications of carbon nitride films.

Carbon nitride films synthesized with an improved reactive ionized cluster beam system

Abstract An improved reactive ionized cluster beam (RICB) deposition system was used to synthesize carbon nitride films. The structure and vibration characteristics of films prepared by the improved or the conventional system were investigated by FTIR transmittance and Raman scattering spectroscopy. A characteristic peak due to the covalent C–N single bonds is found in the films prepared by the improved system. The films deposited by the improved and the conventional systems have similar friction coefficients, but the films deposited by the improved system have better wear resistant properties. The different results are attributed to the different arrival ratio of nitrogen ions to carbon clusters during the deposition.