Solid phase epitaxy processes of amorphized silicon surfaces by Ar-ion bombardment observed “in situ” with ultra-high vacuum tunneling microscopy operated at high temperature

Abstract

A clean Si(100) surface is amorphized by Ar +-ion bombardment. The amorphous layer consists of grains of 0.75–1.6 nm in diameter. Solid phase epitaxy (SPE) processes of the amorphous surfaces are investigated “in situ” using ultra-high vacuum tunneling microscopy. The surface morphology during thermal annealing is affected by the Ar +-ion dose. For a lightly dosed case, (2 × 1) domains surrounded by amorphous regions consisting of grains are observed at 245°C which indicates the onset of SPE. It is found that the surface crystallizes and is smoothened in a layer-by-layer mode. As the temperature increases, the surface roughness is greatly reduced and the whole surface showed (2 × 1) reconstruction at 450°C. For a high-dose case, both (2 × 2) and c(4 × 4) reconstructions are observed in limited areas surrounded by amorphous regions during annealing at around 620°C. Pyramidal structures are observed on a (2 × 1) reconstructed surface during annealing at 830°C. The step structure of the pyramidal structure is clarified.