Structure and phase growth mechanism of vacuum deposited Au/Sn/Bi thin films have been studied by X-ray diffraction
(XRD) method, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). It is found that the
crystallites of Au –Sn intermetallic compounds are randomly distributed in Bi-rich matrix that forms a top-capping layer. The
average sizes of AuSn2 and AuSn4 crystallites are 756 and 667 A˚ , respectively. The lattice constants of AuSn4 in the capping
layer are determined to be a = 6.3694, b = 6.4092 and c = 11.4785 A˚ by Cohen’s analytical extrapolation method. The capping
layer of Au – Sn intermetallic grains in Bi-rich matrix covers most surface area, thus minimizing the exposure of inner Sn atoms
to air and effectively prevents oxidation of the resulting thin film structure.
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