DETERMINATION OF THIN METAL-FILM THICKNESS BY X-RAY-DIFFRACTOMETRY USING THE SCHERRER EQUATION, ATOMIC-ABSORPTION ANALYSIS AND TRANSMISSION REFLECTION VISIBLE SPECTROSCOPY

Direct application of a "modified" Scherrer equation, B = K-lambda/D cos-theta, is made in the determination of the mechanical thickness pf thin highly oriented gold films. A relationship between the measured width at half intensity, B, of the observed x-ray diffraction profile, and the linear crystallite dimension, D (in this case the film thickness), is utilized. The constant K was evaluated experimentally to be 0.9118 from a series of gold films under 600 angstrom in thickness. From a rederivation of the equation, a value of K equal to 0.8859 is adopted for use in this study. The value obtained by Scherrer in the original formulation was 0.9394. Accuracy of this method is dependent on the success in measuring the actual width, at half intensity, of a diffraction peak obtained from the gold thin film. Broadening of the observed Au(111) peak profiles, used in the analysis, were found to be appreciable relative to bulk gold sample profiles. An empirical instrumental broadening correction was applied to the data to obtain improved results. Calculated film thicknesses were compared to those obtained by flame atomic absorption analysis and transmission/reflection visible spectroscopy and were found to be in good agreement. Results from a series of gold film thickness determinations is given, and a description of the methodology is provided regarding determinations of metal film thicknesses in the 100-500 angstrom range.