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 targe ts 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. Ga s contents in the deposited films were measured by electron microprobe analysis. The predictions correctly emulate the observed order-of-mag nitude differences in embedded concentrations among the four gases, an d achieve quantitative agreement with no adjustable parameters in the case of argon. The predictions also correctly forecast the observed ef fects of increasing primary ion energy, which increases the embedded c oncentrations 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 analysi s, which enables reasonable agreement to be achieved simultaneously fo r neon and argon. The concentrations of krypton and xenon are at or be low the limit of detection but agree with prediction at that level. Th e observation of a strong and linear dependence of resistivity on embe dded gas concentration anticipates the future capability to predict th is and other properties for any metal, sputtering gas, and acceleratio n of interest using the general expressions for fast neutrals validate d in this investigation.