Measurement and Manipulation of the Charge State of Adsorbed Oxygen Adatom on Rutile TiO2(110)- 1×1 Surface by nc-AFM and KPFM

Quanzhen Zhang, Yan Jun Li, Huan Fei Wen, Yuuki Adachi, Masato Miyazaki, yasuhiro Sugawara, Rui Xu, Zhi Hai Cheng, Jan Brindiar, Lev Kantorovitch, Ivan Štich

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For the first time, the charge states of adsorbed oxygen adatoms on rutile TiO2(110)-1×1 surface are successfully measured and deliberately manipulated by a combination of noncontact atomic force microscopy and Kelvin probe force microscopy at 78 K in ultrahigh vacuum and interpreted by extensive density functional theory modeling. Several kinds of single and double oxygen adatom species are clearly distinguished and assigned to three different charge states: Oad-/2Oad-, Oad2-/2Oad2- and Oad--Oad2-, i.e. to formal charges of either one or two electrons per atom. Due to the strong atomic-scale image contrast, these states are clearly resolved. The observations are supported by measurements of the short-range force and local contact potential difference as a function of tip-sample distance, as well as simulations. Comparison with the simulations suggests subatomic resolution by allowing to resolve the rotated oxygen p orbitals. In addition, we manage to switch reversibly the charge states of the oxygen adatoms, between the Oad- and Oad2- states, both individually and next to another oxygen, by modulating the frequency shift at constant positive voltage during both charging and discharging processes, i.e. by the tip-induced electric field of one orientation. This work provides a novel route for the investigation of the charge state of the adsorbates and opens up novel prospects for studying transition metal oxide based catalytic reactions.
Original languageEnglish
Pages (from-to)15668-15674
JournalJournal of the American Chemical Society
Early online date16 Oct 2018
Publication statusPublished - 21 Nov 2018


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