Surface Sensitive X-ray Absorption Fine Structure Measurement Using Sample Current Induced by Totally Reflected X-rays

X-ray induced current intensity and Auger electron intensity of a GaAs wafer are measured as a function of the angle of incidence of the x-rays of 2-keV photon energy using synchrotron radiation. It is found that the current intensity curve plotted as a function of the x-ray incident angle resembles the Auger electron intensity curve, but a little difference exists which originates from the difference of the probing depth between the two methods. It is concluded that the Auger electron probes 10-100A depth and the sample current probes 1-10A depth when the incident x-rays are totally reflected. On the other hand, x-ray induced current intensity of a Si wafer is measured as a function of incident photon energy in and out of the total reflection condition, and by this way, x-ray absorption fine structure (XAFS) spectra are obtained. It is found that the XAFS measured using the sample current is more surface sensitive (-5A) than the Auger electron yield (-50A) when the incident x-rays are totally reflected.