抄録
For buried nano structure analyses, we combined a scanning probe microscope with either a UV laser or x-ray light source. Electron trapping process at Si/SiOx buried interface under UV laser irradiation was investigated with an electrostatic force microscope (EFM). The EFM signal synchronized with optical shutter operation revealed electron trapping process with the time constant of 33 ~ 87 s dependent on laser power. These large values reveal a quasi-stable photoionization state of the trapping site. The EFM with the x-ray source provided an x-ray absorption spectrum of the electron trapping site. The inner-shell excitation and following relaxation of trapped electron into the core-hole result in the quasi-stable photoionization state. Since the photoionization can be detected with EFM easily, nano x-ray absorption spectra can be probed with high efficiency. The trapping site had deeper inner-shell energy level owing to electric field between the sample surface and probing tip, resulting in an energy shift of the absorption spectrum. An estimation of electric field due to the trapped electron reproduced the energy shift. The electric field was dominantly determined by a trapped electron in the nanometer area under the tip, and indicated potential for nano spectroscopy of EFM with an x-ray source.
