INERT-GASES IN SPUTTERED TUNGSTEN - A TEST OF PREDICTIVE CAPABILITY

The validity of two previously formulated general expressions for the number and energy of fast neutrals backscattered from sputtering targets is tested by predicting the concentrations of inert gases embedded in sputter-deposited tungsten. Test samples were prepared by ion beam sputtering with neon, argon, krypton, and xenon at 0.6 and 1.2 keV. Gas contents in the deposited films were measured by electron microprobe analysis. The predictions correctly emulate the observed order-of-magnitude differences in embedded concentrations among the four gases, and achieve quantitative agreement with no adjustable parameters in the case of argon. The predictions also correctly forecast the observed effects of increasing primary ion energy, which increases the embedded concentrations of krypton and argon, but decreases the concentration of neon. At the high concentrations of neon (greater-than-or-equal-to 10 at. %), a correction for preferential resputtering enters the analysis, which enables reasonable agreement to be achieved simultaneously for neon and argon. The concentrations of krypton and xenon are at or below the limit of detection but agree with prediction at that level. The observation of a strong and linear dependence of resistivity on embedded gas concentration anticipates the future capability to predict this and other properties for any metal, sputtering gas, and acceleration of interest using the general expressions for fast neutrals validated in this investigation.