Boron, vapor hydrogen halides

Improved versions of OLGA (versions II and III) enabled the applications of corrosive gases such as hydrogen chloride or hydrogen bromide, chlorine, thionyl chloride or boron tribromide vapor etc. This made it possible to synthesize volatile halides and measure their retention times in isothermal quartz columns. 

The deposition of boron phosphide by CVD was carried out in a gas flow system by the thermal decomposition of diborane-phosphine mixtures in a hydrogen atmosphere and the thermal reduction of boron tribromide-phosphorus trichloride mixtures with hydrogen (37). The hydrides are thermodynamically unstable at room temperature and decompose rapidly at above 500°C, which tends to promote homogeneous nucleation by pyrolysis in the gas phase. The halides are thermally more stable than the hydrides, and higher substrate temperatures may be used in the thermal reduction process with essentially no gas-phase reactions. At high substrate temperatures, a phosphorus pressure equal to or greater than the vapor pressure of boron phosphide must be present over the substrate surface to maintain the stoichiometry of the deposit. 

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