The transition of 3C-SiC(001) surface superstructures under Si2H6 gas molecular beam irradiation was dynamically observed by reflection high-energy electron diffraction. Starting from the C-terminated c(2×2) structure, the surface structure changed in the order of c(2×2)→(2×1)→(5×2)→(3×2) with continuing irradiation. The amounts of Si2H6 dose required for the transitions c(2×2)→(5×2) and c(2×2)→(3×2) were approximately 1.16 and 1.36 times as much as that for c(2×2)→(2×1). These ratios are interpreted as the relative amount of the constituent Si atoms of the superstructures. This experimental result supports the simple dimer model for (2×1) (1 monolayer of Si) and the additional dimer model for (5×2) (1.2 monolayer) and (3×2) (1.33 monolayer), respectively, as the proper configurations of these surface superstructures.
Lattice-matched epitaxial growth of 3C-SiC on 6H-SiC substrates using an alternate supply of disilane (Si2H6) and acetylene (C2H2) gas molecular beams in a high vacuum was carried out. On 6H-SiC(0001̄) substrates, epilayers of 3C-SiC(1̄1̄1̄) with a double-positioning twin structure were obtained. On the other hand, single crystalline 3C-SiC(001) epilayers without twin structure were obtained on 6H-SiC(01̄14̄) substrates even at low temperatures down to 850 °C.
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