Ching-Hsong Wu

A study of gas chemistry during hot‐filament vapor deposition of diamond films using methane/hydrogen and acetylene/hydrogen gas mixtures

The composition of the reaction gases in a hot‐filament reactor for chemical vapor deposition of diamond films was analyzed using a gas chromatograph coupled with a quartz microprobe. Concentrations of several hydrocarbons were determined as functions of filament temperature (FT) and the position of the probe relative to the filament for two feed gases, methane/hydrogen and acetylene/hydrogen. The diamond growth rate was measured as a function of FT in both feed gases. The major chemical process in these reaction systems is found to be conversion between methane and acetylene with ethane and ethylene as reaction intermediates. For FT≤1800 °C, the chemical reactivity is low, and no diamond deposition is observed. For FT≥1900 °C, nearly identical chemical composition near the filament is obtained from both feed gases (indicating possible attainment of thermodynamic equilibrium in the gas mixtures), and the measured diamond growth rates are similar. A substantial depletion of carbon in the reaction gases nea...

Laser reflective interferometry for in situ monitoring of diamond film growth by chemical vapor deposition

A simple laser reflective interferometer has been employed for in situ monitoring of diamond film growth in a hot‐filament chemical vapor deposition reactor. This method uses a low power HeNe laser beam reflected at normal incident from the substrate. The high refractive index of the diamond film and the relatively high reflectivity of the Si substrate result in pronounced and easily detected interference oscillations in the reflected beam intensity. The oscillation period provides an accurate and immediate measure of the growth rate. In addition, the variations of the extrema of the oscillations provide an estimate of the quality and surface texture of the diamond films. Significant improvement in research productivity has been realized by using this technique.

The Role of Heavy Hydrocarbons in Cvd Diamond Growth

A mass spectrometric analysis of heavy hydrocarbons (HHCs) during hot-filament CVD diamond growth was performed together with in situ monitoring of the growth rate. Many HHCs were detected and tentatively identified. Of all HHCs studied, only diacetylene shows good correlation with the diamond growth rate under various deposition conditions. Its possible role is discussed.

A Chemical Study of Photo-CVD of Silicon Nitride in Mercury-Sensitized Reactions Between Silane and Ammonia

A photochemical system of mercury-sensitized reactions between silane and ammonia was studied to elucidate the gas-phase chemical processes involved in photo-CVD of silicon nitride. Several transient intermediates were detected and identified as silylated amines by the mass spectrometric isotope labeling method. These compounds containing both Si and N atoms appeared to be the precursors of silicon nitride. The chemical characteristics of silylated amines were studied under different experimental conditions. The reactivity and possible reaction paths for the formation of silylamine are discussed.