Electron microscope investigations of the growth morphology of cadmium arsenide films vacuum deposited at various substrate temperatures

Abstract

The growth conditions for Cd 3As 2 films 0.1–17 μm thick obtained by thermal vacuum deposition were examined. The films were deposited onto NaCl substrates held at temperatures in the range 300–480 K. The platinum-shadowed carbon replica method was used for an electron microscope investigation of the surfaces and cross sections of the films. The microstructure of the films was strongly dependent on the temperature T s of the substrate.For T s below about 400 K ( T s/ T m ⪅ 0.4) the films were amorphous; they consisted of spherical clusters or elongated fibrous-like clusters, or were uniform with a large number of pores and cavities. For T s above 410 K the films were polycrystalline. For 0.4 < T s/ T m < 0.5 ( T s ≈ 410–460 K) columnar growth was observed, whilst for T s/ T m ⩾ 0.5 ( T s ⩾ 460 K) films with large equiaxed crystallites and clearly marked grain boundaries were obtained. The results obtained were discussed using the Movchan-Demchishin and Tornton models of film growth.