The adsorption and thermal decomposition of PH3and NH3on GaAs(100)

The adsorption and thermal decomposition of PH 3 and NH 3 on the Ga-rich GaAs(100)-(4*1) has been studied using temperature programmed desorption, isotope exchange reactions and high resolution electron energy loss spectroscopy (HREELS). At 120 K PH 3 adsorbs molecularly while HREELS and isotope exchange reactions with deuterium suggest that PH 2 is the major species present at 300 K. Molecular adsorption is also observed for NH 3 at 150 K when both the physisorbed and chemisorbed states are formed. HREELS and isotope exchange reactions show that dissociation of the molecular state to form NH 2 occurs when the adsorbed phase is heated.