SCANNING TUNNELING MICROSCOPY AND TUNNELING SPECTROSCOPY OF THE N-TIO2(001) SURFACE

The (001) surface of a highly doped (∼ 1019 cm-3) n-type TiO2 crystal, following polishing, wet etching, and cleaning, was imaged in air with a Pt-Ir tip with a scanning tunneling microscope (STM). Good images of the surface could be obtained with the sample held at negative voltage (positive tip bias), with the high-resolution image showing only Ti atoms. Tunneling spectroscopy, involving the recording of i-V curves and dynamic conductance (di/dV)-V curves with the tip held over a given spot on the TiO2 surface, was also carried out. The resulting curves show electron tunneling into the conduction band and from the valence band, as well as a prominent peak identified as a surface state about 0.3 eV below the conduction band edge. © 1990 American Chemical Society.