Production of Highly Homogeneous Si(100) Surfaces by H₂O Etching:  Surface Morphology and the Role of Strain

Abstract

The etching of Si(100) surfaces in ultrapure water was studied with a combination of infrared spectroscopy (FTIR) and scanning tunneling microscopy (STM). While the FTIR results show that the initially rough H/Si(100) surface becomes highly homogeneous during etching, a phenomenon generally associated with surface smoothing, STM images reveal that the homogeneity is associated with the formation of well-defined etch hillocks. After many hours of etching, the resulting H-terminated surface is composed of stripes of atomically flat Si(100) terminated by etch hillocks bounded by {111}- and {110}-oriented microfacets. Polarization analysis of the Si-H stretching modes provides strong evidence for uniform dihydride-termination of the flat regions, with the narrow (approximately 25 A) width of these stripes allowing for relaxation of steric strain between neighboring dihydrides. The unusual hill-and-valley etch morphology is attributed to the effects of steric strain on the reactivity of sites on the etched surface.

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…For example, missing hydrogen atoms make dangling bonds available; surface impurities, such as hydroxyl groups, can initiate multiple surface reactions, and step edges exhibit different structural characteristics and can serve as a starting point of many chemical processes. The traditional etching-based methods of preparation of monohydride-terminated Si(100)-2×1 lead to mixed surface structures, including dihydride and even facets of hydrogen-terminated Si (111); however, preparation of a highly homogeneous surface covered predominantly with silicon dihydride species is indeed possible [35]. While all these surface structures are extremely interesting and highly reactive, here we will only consider the more readily quantifiable monohydride-terminated Si(100)-2×1 that can be prepared in vacuum and investigated by STM.…”

“…The Si(100) surface looks to be substantially more difficult to prepare in a selective manner and the structure of the surface prepared by etching normally contains a mixture of silicon hydride species, mostly dominated by SiH 2 [385]. Still highly structured, but substantially more homogeneous H-terminated Si(100) surface can be prepared by etching in ultrapure water [35]. However, under UHV conditions it is indeed possible to prepare atomically flat Si(100) surface terminated with monohydride species.…”

Quantum Mechanical Investigation of the Influence of the Local Environment on the Vibrational Properties of Hydrogenated Si(111)

“…This red shift is attributed to a reduced dynamic dipole coupling on microfacets. 6 After exposure to chlorine gas, the Si-H modes are completely removed and two new absorbance features are observed and assigned to the stretch (586 cm -1 ) and bend (528 cm -1 ) modes of Si-Cl. These results indicate that on an atomically flat Si(111) surface, all the hydrogen atoms are exchanged by chlorine atoms with no etching or roughening.…”

Finding Needles in Haystacks: Scanning Tunneling Microscopy Reveals the Complex Reactivity of Si(100) Surfaces

“…32,33 In this case, both the steady-state morphology and the infrared spectrum were complex; both contained some incontrovertible information, but neither was readily assignable in its entirety. The well-resolved H−Si(111) and H−Si(100) transitions in the …”