GAS-PHASE ION-MOLECULE REACTIONS IN MIXTURES OF SILICON AND GERMANIUMHYDRIDES BY ION-TRAP MASS-SPECTROMETRY

The gas phase reactivity of CH3GeH3/SiH4 and GeH4/CH3SiH3 mixtures has been studied by ion trap mass spectrometry at 60-degrees-C and 7.0 X 10(-5) Torr helium pressure. Different reaction pathways have been ide ntified, which are common to the two systems here investigated, but wh ich occur at different extents. In both systems SiH(n)+ (n = 0-3) and GeH(n)+ (n = 0-3) ions show a high reactivity and their abundances dec rease very quickly with the reaction time. In contrast, GeCH(n)+ (n = 3, 5) ions increase their abundances with reaction time, as they are a lso formed in ion-molecule processes, and transport most of the ion cu rrent in the CH3GeH3/SiH4 mixture. Moreover, SiCH5+ ions show an analo gous behavior in the GeH4/CH3SiH3 system, being the base peak at 50-ms reaction time. Remarkable differences are observed in the formation o f species containing new Ge-Si bonds. These are mainly formed by GeH(n )+ (n = 0-2) in the GeH4/CH3SiH3 mixture and by both Si(m)H(n)+ (m = 2 , n = 2-4; m = 3, n = 4-6) and GeH(n)+ (n = 1, 2) in the CH3GeH3/SiH4 one. Moreover, the abundances of ions containing silicon and germanium together show small differences and their abundances are very similar in the mixtures examined. The results have been compared with those o f CH3SiH3 and of the GeH4/SiH4 mixture, for their relevance in photovo ltaic technology.