Fyzikální ústav Akademie věd ČR

The sample to be analyzed acts as cathode in a glow discharge in argon. It is atomized by cathodic sputtering. The sputtered atoms of the sample are excited and ionized in the glow discharge plasma. Upon deexcitation they emit characteristic radiation, the emission spectrum, which is analyzed by an optical spectrometer. Intensities of selected spectral lines reflect the concentrations of the respective elements in the sample and the variations of the intensities with the time of sputtering reflect their depth distributions. Nonconductive layers are analyzed by a radiofrequency discharge, whilst the rf power is fed to the plasma by capacitive coupling. The method is relative. Hence, it is necessary to perform calibration prior to the analysis, i.e., to establish the response generated by certain amount of the element under study, present in the sample. For depth profiling, the sputtering rate must be known for some calibration samples. Detection limits range from fractions of a ppm to tens of ppm for most elements. For hydrogen, oxygen and nitrogen, detection limits are worse.