Characteristics of total reflection X-ray excited current detected with the tip of a scanning tunneling microscope

We have studied the current between a sample subject to irradiation by X-rays and the tip of a scanning tunneling microscope. The dependence on incident angle of both this current and the X-ray fluorescence from the sample was measured for Au, Co and Ti thin films with X-rays of different wavelengths. The angular dependence of the current agreed with that of X-ray fluorescence under vacuum conditions. As a result, it was confirmed that the tip current originated from electrons emitted from the sample surface. It was also found that the tip current depended on both the wavelength of the primary radiation and the type of sample.