Initial stages of interface formation in group IV-IV systems: Sn on Ge(100) and Ge(111)

Abstract

Abstract The initial stages of interface formation between an ultrathin layer of Sn and the Ge(100)c(2 × 4) and Ge(111)-c(2 × 8) surfaces are studied under atomically clean conditions in ultrahigh vacuum. The growth mode is investigated using Auger electron spectroscopy in conjunction with Rutherford backscattering (RBS) techniques. A complex behavior is found: Below a certain critical coverage θ c (1.15 × 10 15 cm −1 ) the Sn deposits in a laminar fashion for a temperature range from 150 to 700 K. For coverages beyond θ c the growth mode is temperature dependent. At 150 K best agreement is found with the data assuming a laminar growth mode. At room temperature Stranski-Krastanov growth is dominant, whereas elevated temperatures lead to successively more severe indiffusion. The Sn deposition begins to order the substrate reconstruction on both surfaces below θ c , however reordering is not complete. The identical ordering behavior observed for Ge(100)-c(2 × 4) and Ge(111)-c(2 × 8) is compared with the behavior of Si(100)-(2 × 1) and Si(111)-(7 × 7) and discussed in terms of the topography of these surfaces.