PREPARATION AND PROPERTIES OF NONCRYSTALLINE SILICON CARBIDE FILMS

Noncrystalline silicon carbide films have been formed by physical sputtering of a hexagonal single crystal of silicon carbide. Electron-microscopy and electron-diffraction studies indicate that the films undergo a transition to polycrystalline cubic silicon carbide (β-SiC) in the temperature interval 850°-900°C. The noncrystalline films were p type and exhibited an irreversible diminution of conductivity by about two orders of magnitude when annealed in the range 200°-600°C. Isothermal annealing in this temperature range produced a decrease in conductivity approximately proportional to the logarithm of annealing time. This kinetic behavior is consistent with the occurrence of thermally activated processes having a distribution of activation energies. An approximate activation energy range for annealing was determined as 0.4-2.3 eV. The irreversible change in conductivity of the noncrystalline films is interpreted as arising from the annealing of structural defects having acceptor-like properties. Since a distribution of activation energies for annealing is observed, it is inferred that a variety of defect types or configurations must be present corresponding to a range of localized energy levels in the forbidden gap. © 1968 The American Institute of Physics.