High resolution synchrotron radiation-based x-ray photoemission spectroscopy study of the Si-rich β-SiC(100) 3×2 surface oxidation

Abstract

We investigate the initial oxidation and interface formation of cubic silicon carbide for the silicon rich β-SiC(100) 3×2 surface reconstruction by high resolution synchrotron radiation-based soft x-ray photoemission spectroscopy. The surface is exposed to low doses of molecular oxygen ranging from 1 up to 10 000 L, at surface temperatures from 25 to 500 °C. Significant formation of SiO2 is found for the surface at room temperature, with the rate of oxidation increasing with temperature. Valence band data and Si 2p core level spectra show that even at low exposures, significant oxidation is taking place, with a surface reactivity to oxygen much larger than for silicon surfaces. The oxidation products, which are grown at very low temperatures (⩽500 °C) include SiO2 as a dominant feature but also substoichiometric oxides Si+1, Si+2, Si+3, and significant amounts of mixed oxide products involving C atoms (Si–O–C).

Initial oxide/SiC interface formation on C-terminated β-SiC(100) c(2×2) and graphitic C-rich β-SiC(100) 1×1 surfaces

“…6͑a͒ for the oxidized 3ϫ2 surface exhibits a much larger amount of oxide products having higher oxidation states 7,9,26,27 compared to the C-terminated c(2ϫ2) surface. 6.…”

“…6. [7][8][9]26,27 Also of interest, the low oxidation states Si ϩ , Si 2ϩ , and Si-O-C are located at higher binding energy ͑by 0.4 and 0.2 eV respec-tively͒ in the case of the C-terminated ␤-SiC͑100͒ c(2ϫ2) surface ͓Fig. 25͒ and ͑bottom͒ C-terminated ␤-SiC͑100͒ c(2ϫ2) surfaces upon oxidation by a 10 000 L of molecular oxygen exposure at 500°C.…”

“…6͑b͒, which remains almost unaffected by the oxidation process for the Si-rich ␤-SiC͑100͒ 3ϫ2 surface with a broadening of the C 1s core level line by Ϸ10%. 9,26,27 The very different behavior of both surfaces suggests that the carbon plane could possibly limit significantly the oxygen diffusion into the silicon carbide lattice, while the high temperatures needed to initiate reaction are likely at the origin of rough interface formation. This further stresses the lack of significant amount of carbon species in the oxides formed on the Si-rich ␤-SiC͑100͒ 3ϫ2 surface reconstruction.…”

Atomic scale control and understanding of cubic silicon carbide surface reconstructions, nanostructures and nanochemistry

“…The β-SiC( 100 C≡C triple bond dimer (carbyne) rows in an sp configuration [30,31,37]. In addition, the C-terminated β-SiC( 100) c(2 × 2) has been shown to behave very differently from Siterminated surfaces upon adsorbate deposition: (i) upon donor adsorbate deposition such as alkali metals, the β-SiC( 100) c(2 × 2) surface become metallic while Si-terminated surfaces remain semiconducting [78,79]; (ii) the Si-rich and Si-terminated β-SiC( 100) surfaces are very reactive to acceptor adsorbates such as oxygen, in contrast to the C-terminated surfaces which remain rather inert [80][81][82]. The C-terminated β-SiC(100) surfaces have also been investigated in detail by ab initio total energy calculations [39][40][41][42].…”

Diffusion of fission products and radiation damage in SiC

“…1×1) surfaces do not oxidize as easily as the Si-rich surfaces, requiring much higher exposures and temperatures [87]. The initial oxidation of Si-rich 3C-SiC(100) (3×2) surface (and also the 6H-SiC(0001)-(3×3) and the 4H-SiC(0001)-(3×3) reconstructed surfaces [88 -91]) shows a very high reactivity rate -approximately three orders of magnitude above those of silicon surfaces [87,92,93]. The other Siterminated reconstructed surface of 3C-SiC and also the other hexagonal SiC polytypes and their surfaces [89] require high oxygen exposures and high temperatures for oxide formation [83].…”