Total energy calculations for silane dissociative chemisorption onto Si(100) and Si(111) surfaces

Total energy calculations based on density functional theory in connection with generalized gradient approximation (GGA) and norm-conserving optimized pseudopotential approximation have been used to investigate the silane che misorption onto Si(111) and Si(100) surfaces. Firstly, the calculated relax ed surface structure of Si(100)-(2x2) has a different dangling bonds enviro nment from that of the calculated relaxed surface structure of Si(111)-(1x1 ). Secondly, our calculated results indicate that SiH4 chemisorption onto b oth Si(100)(2x2) and Si(111)-(1x1) surfaces are energetically favorable and they lead to the formation of SiH3 and H adsorbed on the Si=Si dimer, i.e. Si(100)-(2x2)(SiH3:H) and the surface dihydride SiH2 and 2H, i.e. Si(111)( 1x1)(SiH2:2H), respectively. Finally, the increase of dangling bond density and the absence of adatom backbond breaking are probably two of the key fa ctors controlling the distinct increase in reaction probability for dissoci ative chemisorption of SiH4 onto Si(111)-(7x7) due to Si(111)-(7x7) <-> Si( 111)-(1x1) phase transition at surface temperature greater than 800 degrees C.