Presentation Information

[23p-12F-2]The dipole effect on image mode of TiO2 anatase (101) by AFM at 78K

〇(D)Jiuyan Wei1, Yasuhiro Sugawara1, Yanjun Li1 (1.Osaka Univ.)


AFM,anatase (101),DFT

TiO2 is an important material in many energy-related applications [1]. The image modes on the rutile TiO2 (110) surface have been clarified, but the image modes on the anatase TiO2 (101) surface are still unclear [2]. In this work, we observed the two image modes on the anatase TiO2 (101) surface using NC-AFM at 78K as shown in Fig.1. We found in neutral mode, the O row appears bright while the Ti row is dark. Conversely, in protrusion mode, the contrast is reversed. Different from the image modes on rutile TiO2 (110), only two image modes were observed on the anatase TiO2 (101) surface with 90% for neutral mode and 10% for protrusion mode. The Ir and Ir-TixOy clusters with different terminations were considered in DFT calculations. From the DFT calculations, we found that only the tip apex with H adsorbed on Ir-TixOy cluster image in protrusion mode while the other nine tip apexes were imaged in a neutral mode. Which raised our curiosity, that the H terminations on Ir and Ir-TixOy clusters showed reversed contrast. Combining differential charge density and dipole moment calculation results, we found that the charge redistributes in the gap between the tip apex and surface, forming a dipole moment that causes the reverse image contrast by Ir-TixOy-H tip apex. This study provides insight into the image mechanism on the anatase TiO2 (101) surface, essential for understanding the dipole moment effect on AFM images on metal oxide surfaces.