The deposition of hydrogenated microcrystalline silicon (µc-Si:H) at a relatively high working pressure is performed using a conventional radio-frequency plasma-enhanced chemical vapor deposition method. Correlation of the deposition rate and crystallinity with deposition parameters, such as working pressure, flow rate, dilution ratio and input RF power, are studied. It was found that the deposition rate exhibits a maximum at around 4 Torr and that the crystallinity of films decreases monotonically with increasing pressure. The combination of SiH 4 depletion and high working pressure in the plasma is necessary to improve the crystallinity of films deposited at a high rate. Consequently, a high deposition rate of 9.3Å/s is achieved with high crystallinity and low defect density.

We have developed hydrogenated microcrystalline silicon germanium, which exhibits a red-shifted absorption spectrum relative to hydrogenated microcrystalline silicon, as a candidate material for the bottom cell of amorphous silicon-based tandem solar cells. Optical absorption, x-ray diffraction, and Raman scattering spectra are presented in addition to optoelectronic properties and light-induced changes.

We have investigated the role of hydrogen in hydrogenated microcrystalline silicon (μc-Si:H) formation using hydrogen plasma treatments, in particular examining the possibility of subsurface reaction due to permeating hydrogen atoms, which leads to the crystallization of hydrogenated amorphous silicon (a-Si:H). It is demonstrated that the hydrogen plasma treatment of a-Si:H film on the anode using a cathode covered by a-Si:H film, which is inevitably coated during the deposition period, gives rise to the deposition of μc-Si:H over the a-Si:H layer, i.e., chemical transport takes place. It is also found that the pure hydrogen plasma treatment using a clean cathode induces only etching of the a-Si:H layer. These results imply that the present hydrogen plasma condition does not cause crystallization of a-Si:H but only etching, and that careful experimentation is required to determine the real subsurface reaction due to atomic hydrogen.

Preparation of superhydrophobic nanodiamond and cubic boron nitride films Appl. Phys. Lett. 97, 133110 (2010); 10.1063/1.3494269 Preparation of cubic boron nitride films by radio frequency bias sputtering J. Vac. Sci. Technol. A 13, 2843 (1995); 10.1116/1.579715 Electron optical characterization of cubic boron nitride thin films prepared by reactive ion platingThe preparation of a cubic boron nitride film by physical vapor deposition processes has been investigated. The electron beam guns of a hollow cathode discharge type and a conventional highvoltage type were used for the boron evaporation source. The stoichiometric boron nitride film could be obtained by using a gas activation nozzle. It was necessary to apply the rfbias potential to the substrate to accelerate the formation of the cubic BN phase. It was found that mixing argon gas to the reactant gas N z assists the formation of cubic phase. The film structure was characterized by the infrared absorption spectrum and transmission electron diffraction observation. The microhardness of the cubic boron nitride film obtained was estimated to be about 4000 kg/mm2.

The role of hydrogen atoms in the formation process of hydrogenated microcrystalline silicon (μc-Si:H) by plasma enhanced chemical vapor deposition method has been investigated. Under the present conditions, the etching and the permeation of hydrogen atoms in the subsurface region do not cause the crystallization. The kinetics study of surface morphology and structure in the initial growth of μc-Si:H on an atomically flat substrate indicates that the onset thickness of island coalescence reduced under μc-Si:H formation condition. The results support the ‘surface diffusion model’ in which the surface diffusion of film precursors is enhanced by the sufficient hydrogen coverage of surface and by hydrogen atom recombination energy on the growing surface of the film.

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The bonded hydrogen on the growing surface of hydrogenated amorphous silicon germanium (a-SiGe:H) alloy films has been investigated by use of infrared reflection absorption spectroscopy (IR-RAS). When the alloy films are Si-rich, the surface hydrogen bonded to Si atoms is found to behave in a similar way to those on the hydrogenated amorphous silicon (a-Si:H) films. This means that the thermal desorption stability of surface Si hydride species is not significantly affected by the coexistence of a small amount (typically 20 at.%) of Ge. On the contrary, the desorption behavior of surface hydrogen depends on the alloy composition when the a-SiGe:H films are Ge-rich. A surface reaction scheme is provided in an attempt to explain this series of behavior in surface hydrogen on the a-SiGe:H films.

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