Wet chemical etching of Si(100) surfaces in concentrated NH 4F solution: formation of (2 × 1)H reconstructed Si(100) terraces versus (111) facetting

Abstract

Etching of hydrogen terminated Si(100) wafer surfaces in 40% aqueous NH 4F solution was investigated by scanning tunneling microscopy. In NH 4F solution monohydride terminated Si atoms represent the most stable configuration: Etching proceeds via formation of small, (2 × 1)H dimer row reconstructed (100) terraces and evenly distributed square pyramids with (111) facets of up to 70 Å height, which coexist in equilibrium. Both pyramid formation and the uncorrelated etching of different (100) terraces lead to a continuous roughening of the surface during etching.