DFT study of stepped 4H-SiC{0001} surfaces

Highlights

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DFT simulations of atomic steps on 4H-SiC{0001} in [11–20] and [10–10] directions.

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[11–20] step with C atom on the edge at Si-terminated is the most favourable.C-terminated: structures with CC bonds and Si as the edge atom are preferable.

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C-terminated: atomic and electronic structure is modified only at the very edge.

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Si-terminated: surface buckling and electronic transfer among Si atoms on terraces.

Abstract

The growth of hexagonal crystals of the 4H-SiC and 6H-SiC polytypes occurs in the 〈0001〉 direction. The exposed crystal surface is composed of terraces of the {0001} oriented crystal planes separated by atomic steps of half-unit-cell or single-unit-cell height. We present results of density functional theory (DFT) study of the atomic structure and morphology of the atomic steps formed in the $[10\overline{1}0]$ and $[11\overline{2}0]$ directions on the Si-terminated 4H-SiC{0001} and the C-terminated 4H-SiC$\{000\overline{1}\}$ surfaces. On the latter surface atomic and electronic structure is modified only in the nearest neighbourhood of the step whereas the structure of the terrace is almost unchanged compared to that of the smooth stoichiometric surface. In contrast, on the Si terminated surface for both types of the applied model steps and on the widest terraces considered a substantial surface buckling is observed in the regions between steps. We calculated ledge energy and found that $[11\overline{2}0]$ step with C atom on the edge at Si-terminated surface is the most favourable energetically of all examined cases.

Keywords

Surfaces

Semiconductors

DFT

Steps

Atomic structure

Electronic structure

Source:ScienceDirect

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