Invited

Molecular adsorption on anatase TiO₂(101) studied by submolecular imaging technique with Si cantilever AFM

T. Shimizu^1,2, M. Todorović³, O. Stetsovych¹, C. Moreno¹, R. Perez³, and O. Custance¹

¹National Institute for Materials Science, Tsukuba, Japan

²JST-PRESTO, Saitama, Japan

³Dpto. de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Spain

Submolecular imaging using frequency-modulation (FM) atomic force microscopy (AFM) has recently been established as a stunning technique to reveal the chemical structure of unknown molecules, to characterize intra-molecular charge distributions, and to observe chemical transformations. So far, most of these feats were achieved on planar molecules using the so-called qPlus sensor, a specially designed quartz AFM sensor.

Here, we report a novel imaging method using multi-pass routine to achieve submolecular resolution on three-dimensional molecules and structures with a silicon (Si) cantilever-based AFM operated with large oscillation amplitudes. At variance with previous implementations, this method allows us to simultaneously image both intra-molecular structures and the atomic arrangement of the substrate [1]. Force volume measurements over C₆₀ molecules clarify the validity of our method to achieve submolecular resolution. Using this technique as well as information obtained in our previous study of clean anatase TiO₂(101) surface [2], we have investigated adsorption of pentancene molecules on terraces and steps of anatase TiO₂(101) [3]. Based on comparison with theoretical calculations, we obtain an insight into substrate-molecule interaction and probe tip termination.

Figure 1: (a) Topographic AFM image and (b) multi-pass frequency shift image of pentacene molecules adsorbed on terraces and steps of the anatase TiO₂(101) surface obtained at 77 K. Image size is 20nm×20nm.

[1] C. Moreno et al., Nano Lett. 15, 2257 (2015).

[2] O. Stesovych et al., Nat. Commun. 6, 7265 (2015).

[3] M. Todorovic et al., in preparation.