STM analysis of wet-chemically prepared H-Si(001) surface

Microroughness of wet-chemically prepared Si(001) surfaces was measured in an atomic scale by ultrahigh vacuum scanning tunneling microscopy (UHV-STM). On the surface treated by 2.5%-HF solution (pH = 2), the root mean square (rms) value for the surface roughness was about 1.4 Angstrom, whose surface exhibited the unclear steplike structure of Si(001) surface. On the other hand, the STM images on the surface treated by HF:HCl = 1:19 solution (pH < 1) under the controlled removal of the oxide layer, the SRM image exhibited clear step structure without etch pits, and the rms value for the surface roughness is the same as that of the 2.5% HF treated sample.