Structure and properties of sequentially sputtered molybdenum–tin films

Rotating a water-cooled substrate rapidly under Mo and Sn sputter sources made sequentially sputtered molybdenum–tin thin films. The layer thickness deposited during each circuit under each source was selected between 2 and 20 A and films of several micrometers overall thickness were prepared. The produced films were characterized using wide-angle and small-angle X-ray scattering, 119 Sn Mossbauer spectroscopy, differential scanning calorimetry and transmission electron microscopy. Films of three major types are observed: (1) homogeneous crystalline body centered cubic Mo 1− x Sn x is produced when x is less than approximately 0.45 and when the layer thickness deposited in each pass under the targets is small; (2) nanocrystalline BCC Mo 1− x Sn x having x approximately equal to 0.45 coexisting with nanocrystalline tin when the overall tin content is greater than 45% atomic and the layer thickness deposited in each pass under the targets is small; and (3) lamina of composition modulated Mo 1− x Sn x disturbed by nanoscopic clusters of tin when the overall tin content is greater than approximately 40% atomic and the layer thickness of Mo deposited in each pass is greater than approximately 6 A. This is the first report of BCC Mo 1− x Sn x for 0≤ x ≤0.45. A ‘phase diagram’ of the observed film types is presented.