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Chemical reactions of copper(II) oxide (CuO) with monosilane (SiH4) and arsine (AsH3) at room temperature were investigated. Both hydrides were trapped by CuO. Adsorption capacities of CuO for SiH4 and AsH3 were increased in relation to the specific surface areas of CuO. The capacity for AsH3 was estimated to be ten times as large as that for SiH4. From the surface analyses of the CuO exposed to SiH4 and AsH3, arsenic was found to a depth of 30 A from the surface, although silicon was detected only on the surface. The CuO surface was covered with a Si-O layer formed by the reaction of SiH4 with CuO. Thus, SiH4 did not diffuse into the inner parts of the CuO. On the other hand, AsH3 was considered to have penetrated into the CuO because volatile H3O was formed by the reaction of AsH3 and CuO.

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Ammonia (NH 3 ) as a precursor for epitaxial nitride films is required to be free of trace oxygenated impurities, such as CO 2 , that have been shown to negatively affect growth processes and device performance. Carbon dioxide can react reversibly with the NH 3 gas to form ammonium carbamate, NH 4 COONH 2 (a solid with low solubility in liquid NH 3 ) and, therefore, can be present in cylinder sources both in the free and chemically bound form. A gas chromatograph (GC)-based method has been developed to accurately quantify the total CO 2 content in both vapor-and liquid-phase NH 3 streams. A heated GC-sampling manifold is used to thermally decompose any NH 4 COONH 2 present in the sample or calibration standard so that all CO 2 is analyzed in its free form. Several commercial cylinder sources maintained at room temperature were analyzed by this method, and in all cases, equilibrium concentrations of Ͻ75 parts-per-billion by volume (ppbv) CO 2 were present in the gas phase as long as residual liquid was present. Slightly higher concentrations were found in the liquid phase, and upon exhaustion of the liquid phase and heating, CO 2 levels strongly increased to parts-per-million by volume (ppmv) levels. The excess CO 2 is likely adsorbed on the cylinder walls or dispersed in the liquid as solid NH 4 COONH 2 . These results are consistent with thermodynamic calculations based on equilibrium data for the carbamate system available in the literature. To meet the purity requirements of organo-metallic vapor-phase epitaxy processes, the performance of an adsorbent-based purifier that is capable of removing residual CO 2 in both free and chemically bound forms from NH 3 streams is discussed.