16:30 〜 16:45
▲ [14p-414-13] Investigation of Tunneling Current and Local Contact Potential Difference on O-TiO2(110) surface by AFM/KPFM
キーワード：TiO2(110), density of states, contact potential difference
Oxygen molecular on TiO2 has attracted much attention and become a research model due to its importance in a variety of catalytic processes. Molecular oxygen is one of the main oxidizing reagents in many catalytic reactions, and also considered as an electron scavenger which is believed effectively to facilitate these reactions. However, the distribution of surface potential after O2 dissociation and reactive site etc., haven’t been clarified yet. To clarify the above questions, measurement of local contact potential difference (LCPD) on O-TiO2(110) surface at an atomic level are useful. In addition, clarification of oxygen on TiO2 is necessary to understand the fundamental mechanism. In this study, to investigate charge transfer on oxidized TiO2(110) surface with atomic resolution, we propose a method of simultaneously measurement of tunneling current and the LCPD by atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM).
In the experiment, the method of FM-KPFM without bias voltage feedback was performed [1] at the constant height mode to remove the crosstalk of the surface topography. The DC bias added with ac bias voltage was applied between the tip and sample. The frequency shift was measured by phase locked loop (PLL). Two lock-in amplifiers were used to measure frequency shift at fω and f2ω. The LCPD signals were numerically calculated from the divided results of the fω and f2ω signals. As a result, the LCPD image with atomic resolution and tunneling current image were observed simultaneously. Figure 1 shows the frequency shift, current and LCPD images on TiO2(110) surface.
In the experiment, the method of FM-KPFM without bias voltage feedback was performed [1] at the constant height mode to remove the crosstalk of the surface topography. The DC bias added with ac bias voltage was applied between the tip and sample. The frequency shift was measured by phase locked loop (PLL). Two lock-in amplifiers were used to measure frequency shift at fω and f2ω. The LCPD signals were numerically calculated from the divided results of the fω and f2ω signals. As a result, the LCPD image with atomic resolution and tunneling current image were observed simultaneously. Figure 1 shows the frequency shift, current and LCPD images on TiO2(110) surface.