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

Abstract

The surface structure of Si(100) after carbon deposition has been studied by scanning tunnelling microscopy (STM) at a substrate temperature of 600°C. At carbon coverages of about 1/3 monolayer (ML) a c(4×4) structure covering the entire surface is obtained. Higher coverages give rise to island formation and to a 2×1 structure of the surrounding substrate surface. The surface morphology after subsequent Si epitaxy is documented and depends on the initial carbon concentration. The c(4×4) structure (without islands) can be observed even after additional 3-nm thick epitaxial Si is deposited. The island formation of Ge on Si(100) at 550°C – after carbon (0.1–0.3 ML) predeposition – leads to smaller islands of about 5 nm in size than without carbon. The islands are arranged on a 2×n structure with missing dimers and missing dimer rows and the island density is about 1–3.6×10 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 the island neighbourhood.