Determination of the depth of impurity atoms in bulk material by proton‐induced x rays

摘要

We attempt to determine the target composition of one homogeneous layer of foreign atoms in bulk material by comparing the yields for proton‐induced x rays at two different energies. The problem is formulated mathematically and an approximate method of solution is given. The method uses a calibration curve which is given by the ratio of the yields at the two energies for a pure foil of the foreign material of known surface density. Both thickness and location in depth of the foreign layer can be determined. The method is applied to sandwich targets (Ag‐Cu‐Ag and Ge‐Cu‐Ge) of known layer thickness (determined by Rutherford backscattering). By measuring the same target under various conditions, and by comparison to backscattering, it is shown that a mean depth of Cu atoms of about 1 mg/cm2 can be measured to an accuracy of about 4%.