Preparation and Properties of Noncrystalline Silicon Carbide Films

Abstract

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.