HIGH-RESOLUTION TIME-OF-FLIGHT MASS-SPECTROSCOPY FOR MONITORING SURFACE AND GAS-PHASE PHOTOCHEMICAL-REACTIONS - SI2H6 ON SI(100)

A high-resolution time-of-flight mass spectroscopy using single-bunch operation of the synchrotron radiation source was applied to monitor the photochemical reactions on Si(100) exposed to Si2H6. H+ ions emitted from surface, subsurface, and gas phase were separated in the high-resolution spectra. The subsurface-originating H+ is from hydrogen bound to impurity atoms and the intensity of its peak is enhanced with increasing bias voltage on the substrate. The surface-originating H+, affected by Si2H6 chemisorption, is bound to Si atoms. The position of the spectral peak due to H+ generated by photolysis from gas-phase Si2H6 is the same as that of the peak due to H+ emitted from the surface. The relative contributions of surface and gas sources can be evaluated from the pressure dependence of the spectral peaks.