Oxygen Surface-Density Measurements Based on Characteristic X-Ray Production by 100-keV Protons

The oxygen-K x-ray yield from known thicknesses of aluminum oxide (1–70 μg O/cm2), bombarded by 100-keV protons, indicates that oxygen surface density may be measured over the range from 50 to 0.004 μg/cm2. At the lower limit, background is 50% of the signal. In thin oxide layers where proton energy loss and x-ray absorption are negligible, the x-ray yield I (x rays/proton) is related to the oxygen surface density t (μg/cm2) by I=(2.9×10−6)t.