The influence of carbon on the surface morphology of Si(100) and on subsequent Ge island formation

The surface structure of Si(100) after carbon deposition has been studied b y scanning tunnelling microscopy (STM) at a substrate temperature of 600 de grees C. At carbon coverages of about 1/3 monolayer (ML) a c(4 x 4) structu re covering the entire surface is obtained. Higher coverages give rise to i sland formation and to a 2 x 1 structure of the surrounding substrate surfa ce. The surface morphology after subsequent Si epitaxy is documented and de pends on the initial carbon concentration. The c(4 x 4) structure (without islands) can be observed even after additional 3-nm thick epitaxial Si is d eposited. The island formation of Ge on Si(100) at 550 degrees C - after ca rbon (0.1-0.3 ML) predeposition leads to smaller islands of about 5 nm in s ize than without carbon. The islands are al-ranged on a 2xn structure with missing dimers and missing dimer rows and the island density is about 1-3.6 x 10(11) cm(-2) (0.3 ML C predeposition). Subsequent Si deposition reveals , that the strain field around the islands slows down the growth rate in th e island neighbourhood. (C) 1998 Elsevier Science S.A. All rights reserved.