Oxide-thickness determination by proton-induced x-ray fluorescence

A discussion of the principles of oxygen surface density and, hence, oxide-thickness determination by proton-induced x-ray flurescence is followed by results of several applications of the technique. This technique has been shown to be useful for oxide thicknesses between ten and a few thousand Å. In practice, monoenergetic proton beams with energies between 100 and 400 keV produced characteristic x rays of all elements near the surface of aluminum, erbium dideuteride, copper, and stainless-steel specimens; these x rays were detected with a high-resolution Si(Li) detector. The oxygen Kα x-ray yields (x rays/proton) for these specimens were calibrated using known oxygen surface densities and, hence, oxide thicknesses on aluminum.