AN ESDIAD STUDY OF CHEMISORBED HYDROGEN ON CLEAN AND H-EXPOSED SI(111)-(7 X 7)

The chemisorption of H on Si(111)-(7 × 7) has been studied by digital ESDIAD and temperature programmed desorption methods. It has been found that residual H in the bulk of the Si(111) can be transported to the surface upon annealing to temperatures above ∼ 1000 K. The adsorption of atomic H on Si(111)-(7 × 7) results in a mixture of monohydride and polyhydride species as detected by H+ ESDIAD. Thermal desorption from the H-saturated surface liberates β3-, β2- and β1-H2 species SiH4(g). Heating the H-saturated surface to 1040 K results in a significant disordering of the surface, leading to Si sites which produce highly tilted SiH bond directions. The occupation of these sites with H produces surface species exhibiting high polar angles from the surface normal for H+ desorption by an ESD process with a high ionic cross section compared to the cross section observed for normal mono- and polyhydride surface species. © 1990.