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Sputtered metal films grown in different discharge environments are subject to different degrees of energetic particle bombardment during film growth, resulting in different microstructure and subsequent thin-film properties. The effect on film structure of energetic gas neutrals, backscattered from the sputtering target, together with the role of sputtered neutral metal atoms and those Penning ionized in traversing the plasma, are evaluated in different pressure regimes and under different biasing conditions. It will be shown that the film morphology, degree of texturing, and anisotropic lattice distortions change in a systematic way depending on En, the energy delivered to the growing metal film surface per arriving metal atom. En changes predictably in different discharge pressure regimes as do the resultant film structures and properties.

Rheotaxial growth and thermal oxidation (RGTO) for depositing thin films is a recognized technique in preparing gas sensitive semiconducting oxides. This paper presents a study performed by x-ray diffraction and scanning Auger microscopy of the mechanisms of growth and formation of the thin films of the new ternary compound Sn1−xFexOy with an iron content in the range O < x < 25 at. %. A structural model of this compound, which is found to be stable over a very large range of Sn/Fe ratios, can be derived by partially substituting Fe3+ ions in Sn4+ sites. This is an easy substitution in view of the similar values shown by the ionic radii (Fe3+ = 0.64 Å, Sn4+ = 0.71 Å) and the Pauling electronegativity (Fe3+ = 1.8, Sn4+ = 1.8) of these two ions. Experimental data, showing that this material is an excellent CO sensor, are reported.