Hydrogen adsorption on Si(100)-2×1 surfaces studied by elastic recoil detection analysis

Scanning tunnelling microscopy of the interaction of hydrogen with silicon surfaces

“…However, many workers have observed that the 7 × 7 superstructure remains intact following adsorption [50], which suggests that an unrestricted etching reaction cannot be responsible for the observed hydride species. Limited reactivity is also consistent with the observed saturation behaviour of hydrogen on this surface [48,52]. Initial STM studies of hydrogen adsorption on the Si(111)-7 x 7 surface were largely concerned with small hydrogen exposures.…”

“…This assignment was believed to be consistent with the then understood saturation coverage of 1.5 monolayers [48]. However, a more recent measurement yielded a value close to 2 monolayers [93], placing doubt on the structural assignment of the 1 x 1 surface suggested by Chabal and Ragavachari.…”

“…Despite the fact that the coverage associated with such a surface is 1-33 monolayers, this explanation was generally accepted. However, a recent measurement of the saturation coverage by Oura et al [93] obtained a value close to 2 monolayer. STM studies of this surface observed the slow transformation of the 2 ×l monohydride surface to a poorly ordered 1 x 1 surface [21,107].…”

“…Following reaction of the, 19 dangling bonds per unit cell, the surface coverage is 19/49 or about 0.4 monolayers. However, the apparent saturation coverage of hydrogen on this surface is between 1.25 and 1.5 monolayers [48,52]. Sakurai et al [54] suggested that hydrogen uptake beyond that associated with dangling bonds is due to surface defects.…”

“…It is the limited number of such strained bonds that is responsible for the observed saturation behaviour. Culbertson et al [48] reported a saturation coverage of 1.25 monolayers while more recently Oura et al [52] measured a value of 1.5 monolayers. Since the mode of strained bond relaxation and hence the nature of the hydride species on the surface is dependent on the exposure conditions, it is not surprising that different measurements of the apparent saturation coverage yield different values.…”