Indium overlayers on clean Si(100)2×1: Surface structure, nucleation, and growth

Abstract

The structure, nucleation, growth mechanisms, and morphology of In overlayers on clean Si(100)2×1 surfaces have been investigated as a function of In coverage θ and deposition temperature T s using reflection high-energy eletron (RHEED), low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and scanning electron microscopy (SEM). The surface phase diagram for In on Si(100) was determined. Over the entire temperature range investigated, 30 to 600°C, In was found to interact with clean Si(100) surfaces through a Stranski-Krastanov mechanism in which the initially deposited In nucleated and grew two-dimensionally up to a coverage of between 2 and 3 monolayers (ML), depending upon T s, after which three-dimensional islands were formed. The structure of the two-dimensional layer, as well as the morphology of the islands, was dependent upon θ and T s. At deposition temperatures between 30 and 150°C, In formed a two-dimensional gas at coverages below 0.1 ML and an In(2×2) structure with chains of In dimers along 〈011〉 directions at coverages between ≈0.1 and 0.5 ML. Further increases in θ resulted in a transition to an In(2×1) structure while single-crystal elongated polyhedral-shaped islands exhibiting preferential growth along [011] and [01 1 ] directions were obtained at coverages above ≈ 3 ML. The introduction of even minute amounts of contaminants (≈ 0.01 ML) prevented the formation of the Si(100)2×2-In phase and resulted in the growth of epitaxial hemispherical fcc In islands on Si(100)2×1-In at θ ≳ 2 ML. For T s between 150 and 420°C, the initial In overlayer on clean Si(100) surfaces exhibited an In(3×4) structure and emispherical In islands were observed at coverages ≳ 2 ML. Above 420°C, a disordered In layer formed on top of the In(3×4) phase at θ≳0.5 ML while (310) Si facets were observed at θ > 0.5 ML and T s > 550°C. Indium deposition on Si(100)3×4-In surfaces (formed at T s > 150°C and then cooled to T s < 150°C before further deposition) resulted in the formation of hemispherical-shaped fcc In islands with a much higher number density than was observed for the elongated polyhedral-shaped In islands grown on Si(100)2×1-In surfaces under the same deposition conditions.