Influence of a pre-deposited carbon submonolayer on the Ge island nucleation on Si(001)

Si surfaces manipulated by a carbon (C) pre-deposition have been used to modify the growth morphology of Ge islands. In situ reflection high-energy electron diffraction and x-ray photoelectron diffraction and ex situ atomic force microscopy studies have been conducted for constant C seeding and varying growth temperatures and Ge coverages, with the aim of deepening the understanding of the relevant Ge quantum dot formation. With temperatures ranging from 400 to 600 degreesC, well structured Ge islands grow in a Volmer-Weber mode as soon as 0.4 ML of C and 1 ML of Ge are deposited. Strongly modified behaviors are nevertheless observed by changing the Ge growth temperature from 500 to 600 degreesC. By increasing the Ge coverage from 1 to 6 ML at 500 degreesC, the island height increases at constant density, whereas, at 600 degreesC, a strong reduction of the density is observed, with a three-dimensional-two-dimensional transition probably due to a partial Ge intermixing in the Si matrix. These different nucleation schemes are connected with varying evolutions of the initial C-related c(4x4) reconstruction. (C) 2003 American Institute of Physics.