CVD of boron and dichloroborane formation in a hot-wire fiber growth reactor

Chemical vapor deposition (CVD) of boron by hydrogen reduction of BCl, on a hot tungsten substrate was investigated in a parallel flow reactor. Effect of substrate temperature (1100-1250 degreesC) on the relative rates of for mation of BHCl2 and boron was observed by the on-line analysis of the react or effluent stream composition using an FT-IR spectrophotometer. It was con cluded that BHCl2 was majorly formed in the gas phase within the thermal bo undary layer adjacent to the substrate with possible contribution of surfac e reactions at higher temperatures. Comparison of results obtained in the i mpinging jet and parallel flow reactors indicated the significance of diffu sion resistance in the parallel flow system. Tubular flow reactor experimen ts indicated that BHCl2 formation reaction started at temperatures as low a s 350 degreesC and reached equilibrium in less than a second at temperature s over 420 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.