Etching of Si(111)-(7×7) and Si(100)-(2×1) surfaces by atomic hydrogen

We present scanning tunneling microscopy (STM) studies of the etching behavior of the surfaces of Si(111)-(7×7) and Si(100)-(2×1) by atomic hydrogen. Etching proceeds via the formation of volatile SiH4 through a two-step mechanism in which the H atoms react with SiH2 and SiH3 species on the surface at room temperature. By measuring the area of etch pits in the STM images taken under the same flux conditions, the etching of Si(100) is determined to be nearly three times faster than that of Si(111) because intermediate hydride products are more readily stabilized on the (100) surface.