A theoretical model and experimental measurements of the X-ray emission from thin films generated by an electron beam were analyzed and compared. Ionization correction factors for the thin films and for substrate effects were developed to calculate intensity ratios of film and film on substrate to pure bulk intensities.
The fraction of electrons transmitted through gold, silver, and copper with energy greater than the critical excitation energy was measured as a function of thickness and primary electron energy. The characteristic X-ray intensities from gold on bismuth, palladium, nickel and aluminum Substrates; copper on palladium, nickel and aluminum substrates; and silver on aluminum substrates were measured and intensity ratios to pure bulk intensities were compared to the model prediction. The prediction of the X-ray intensity ratios were approximated by a simple electron balance model for the ionization correction factors and the consideration of electron energy distributions did not alter the predictions significantly.
An empirical conversion parameter, following the bulk procedures of Ziebold and Ogilvie, was determined experimentally for alloy thin films of gold and silver on oxidized silicon substrates for films between 500 and 2000 Å. The prediction of the parameter from the intensity model is in fair agreement with the measured values. However, the empirical conversion parameter could prove to be useful for thin film analysis.