The Mass Spectrometric Investigation of the Chemical Vapor Deposition Process for Alumina.

摘要

Mass spectrometric analysis has been made of the chemical vapor deposition process for alumina from gaseous reagents of Cl2/H2 over aluminum metal and H2O/O2 or oxygen. The experiments were performed in a specially designed concentric furnace followed by a high pressure sampling technique and mass spectrometric detection. From the analysis of Al2O3 deposits, it is found that opaque to transparent polycrystalline alumina can be prepared by a proper combination of gaseous reagents at selected temperatures. The optimum operating conditions and appropriate gaseous mixtures are described and recommended. Mass spectra reveal that the major aluminum chloride specie at deposition temperatures above 1000 C is AlCl, contrary to earlier literature. The formation of solid Al2O3 in the present CVD process is a surface nucleation phenomena and no vapor phase homogeneous nucleation occurs. The overall reaction is believed to be principally: 2AlCl(g) + H2O(g) + O2(g) = Al2O3(s) + 2HCl(g); and, to a lesser extent, 2AlCl(g) + 3H2O(g) = Al2O3(s) + 2HCl(g) + 2H2(g). (Author)