An X-ray profile analysis on the growth imperfections and internal strains in vapour-deposited lead films

Abstract

Detailed X-Ray line profile studies have been performed on thin films of lead (thickness range ~30-900nm), vapour-deposited onto glass substrates, under high vacuum (~10-6 Torr). The films reveal unusually high orientation along [111] over the whole thickness range. Both Warren-Averbach and Williamson-Hall analysis have been adopted W-H plot shows a near-isotropy in strain broadening observed at higher film thickness with predominant microstrain contribution. W-A analysis shows that the crystallite sizes are in the range of 225-2700Å and the rms strains are of the order of 10-4. The residual stresses have been found to be small and slightly higher than that due to thermal stress. The combined peak shift, peak asymmetry and peak broadening analyses show the absence of both intrinsic and extrinsic stacking faults while growth faults are found to be present in smaller concentrations. The lattice parameter changes are small and are of the order of 10-4. The dislocation density calculated from crystallite sizes and rms strains is of the order of 1010 cm/cm3 Dislocations are the primary cause of strain broadening. The dislocation arrangement changed considerably from a non-random to a near-random distribution with increasing thickness. The microstrain distribution function was however found to be almost Gaussian.