[21a-P7-1~10] 6.6 Probe Microscopy

[21a-P7-6] Subsurface Charged Regions on TiO₂(110) Observed by NC-AFM/KPFM

〇(PC)Jo Onoda^1,2, Chi Lung Pang³, Yurtsever Ayhan⁴, Yoshiaki Sugimoto^1,2 (1.Univ. Tokyo, 2.GSE, Osaka Univ., 3.UCL, 4.GSES, Osaka Univ.)

Keywords:atomic force microscopy,Kelvin probe force microscopy,titaniumu dioxide

TiO₂ has been investigated intensely since the 1970s when it was discovered that it is an active photocatalyst. It is becoming more and more apparent that both extrinsic subsurface dopants and intrinsic subsurface defects can dramatically modify the behavior at the surface. Here, we use noncontact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM) to study subsurface charges and their effect on the adsorption of H adatoms on 0.05% wt Nb-doped rutile TiO₂(110). The subsurface charges add an additional electrostatic force between the sample and tip so that they appear as hillocks in the NC-AFM topography. KPFM directly visualize the presence of charged subsurface impurities. These charged regions, which are assigned to single positively-charged ions, repel the positively-charged H adatoms that normally decorate the surface. Charged subsurface dopants may therefore be exploited as a means of restricting certain charged adsorbates from parts of the surface and perhaps other adsorbates could even be confined in those regions.