Epitaxial Growth of Metastable Facf—Centered Cubic Co on (111)Si with A Thin Intermediate Cu Layer

ABSTRACTMetastable face—centered cubic (fcc) Co was grown epitaxially on (111)Si with an intermediate Cu layer in an ultrahigh vacuum chamber at room temperature. The metastable fcc—Co was grown to extend to a thickness of 30 nm. Polycrystalline and epitaxial hexagonal close—packed (hcp) Co was grown on (111)Si without and with 3 nm or thicker intermediate Cu layer, respectively. The key to the successful growth of fcc—Co is to deposit Co directly onto a thin (2 nm or thinner) interface compound (—Cu, which is of hcp structure and consisting of 11.2 to 14.0 at.% Si. The growth of the metastable phase is attributed to the attainment of an appropriate electron/atomratio at the interface to favor the formation of the fcc—Co.

ARXPS studies of SiO2-SiC interfaces and oxidation of 6H SiC single crystal Si-(001) and C-(001) surfaces

The main puzzle in oxidation of hexagonal SiC is the slower rate of the Si-terminated surface as compared to the C-terminated surface, which is blamed on an unknown interface compound. ARXPS is a unique method to identify minor amounts of interface compounds, especially for smooth surfaces. Our ARXPS analysis of oxidized Si-(001) and C-(001) surfaces of 6H SiC reveals the interface oxide Si4C4−xO2 (x < 2), likely a reaction product of a peroxidic O2-bond to a SiC double layer. Si4C4−xO2 occurs in larger thickness (≃1 nm) at the slowly oxidizing Si-(001) surface, whereas the C-(001) surface shows smaller amounts, diminishing fast with oxidation above 1000 K. Evidence is presented that with increasing amount of Si4C4−xO2 the oxidation of SiC to SiO2 is reduced. ARXPS is consistent with a layer of SiO2 containing less than 3% Si4C4O4 being an oxidation product of Si4C4−xO2. At the surface of SiO2, graphite and some Si4C4O4 exist, aside from standard adsorbates.