Behavior of Ga atoms on Si(001) surface at high temperature

Abstract

The growth processes and structures of Ga layers formed on a Si(001) surface have been studied by scanning tunneling microscopy and low-energy electron-diffraction analysis. Si(001) wafers cut at 0.5° toward the [110] direction and showing a double-domain surface structure were used as substrates. Ga atoms from a Knudsen cell were deposited on substrates maintained at 600°C. In a Ga coverage range between 0.15 and 0.30 monolayer (ML), a Si(001)2×3–Ga structure composed of Ga ad-dimers rows was formed. In this coverage range, the ratio of the surface area of the TA terrace to that of the TB terrace (terraces where Si dimer rows run parallel and perpendicular to the step, respectively) was changed by step rearrangement, and biatomic steps were formed partially. Such step rearrangement can be explained by the substitution of Si atoms by Ga atoms at kinks. On the TB terrace, Ga ad-dimer rows along the SA step filled the terrace, while those along the SB step (an SA step where Si dimer rows on the upper terrace run parallel and perpendicular to the SB step) terminated partly. At a Ga coverage of about 0.48 ML, a Si(001)2×2–Ga single-domain structure occupied almost the entire surface (accounts for 97% of the whole surface area). On the terraces on the surface, Ga ad-dimer rows run parallel to step edges. Bright irregular protrusions were observed on biatomic step edges, while small hazy protrusions attributed to adatoms were observed on the ledge and edge of the step.