Epitaxial growth of Cu onto Si(111) surfaces at low temperature

Abstract

Epitaxial growth of Cu onto the Si(111) surface was studied using reflection high-energy electron diffraction. To understand the mechanism of epitaxy, its dependence on substrate temperature and deposition rate was systematically investigated. The measured Cu–Cu atomic distance of the surface layers deposited at room temperature (RT) and 160 K is smaller than the lattice constant 2.56 Å of Cu(111) up to 10 and 3 monolayers (ML), respectively. This change is attributed to the silicide formation. The change in the intensity oscillations when the temperature is decreased from RT to 160 K was seen to be identical to intensity oscillation changes observed while increasing the deposition rate to 50 ML min −1 and holding the substrate at RT. The intensity oscillations are irregular up to 8 ML, and become regular >8 ML. The regular period after 8 ML is smaller than the thickness of the Cu(111) layer. A model for growth of Cu on the Si(111)-(7×7) surface at 160 K is proposed. The changes in periodicity are due to the silicide, defect formation, and partially two-dimensional layers.