Atomic-level characterization of metal/oxide interfaces (Ti, Fe, Ni, Ag, Au/Al2O3, MgO, TiO2): a background for nanomaterial design for catalysis to photonics

S.A. Khubezhov, I.V. Silaev, A.P. Bliev, D.D. Kibizov, G.S. Grigorkina, E.N. Kozyrev, R.O. Askerov, I.N. Goncharov, D. Sekiba, S. Ogura, K. Fukutani, T.T. Magkoev
North Ossetian State University,
Russian Federation

Keywords: metal/oxide nanostructures, material contact interface, surface characterization, electron spectroscopy, scanning probe microscopy, nanomaterial design

Summary:

Corresponding author, e-mail: t_magkoev@mail.ru (Tamerlan Magkoev) Metal/oxide systems are widely used in different application fields, such as heterogeneous catalysis, nanoelectronics, sensing techniques, optics, photonics, etc. [1]. Despite of a very extensive research in this field, the main challenge is still detail atomic level understanding of the physical and chemical effects in such systems – the effects which determine their technological relevance. In relation to this, the aim of the present work was to determine the properties of metal nanoclusters (Ti, Fe, Ni, Ag, Au) deposited on oxide supports (Al2O3, MgO, TiO2), and of the corresponding metal/oxide interface. The systems were prepared in ultra-high vacuum and were characterized by a set of complementary Surface Science techniques: X-ray, Auger, infrared and electron energy loss spectroscopy (XPS, AES, RAIRS, EELS) and scanning tunneling microscopy (STM). The oxide films (Al2O3, MgO, TiO2) of 0.6 to 3 nm thick were formed on Mo(110) substrate by well-known procedures of reactive growth. The main effect under successive metal deposition on the oxide supports for all systems studied is a quite noticeable metal concentration threshold separating ionic and atomic character of deposited metal specie. Separated metal atoms and small clusters deposited on oxide supports acquire cationic character, presumably due to interaction with surface defects. As the defects are being covered with increasing of the surface concentration of metal atoms their effect decreases, so the interface charge transfer effect weakens, further accompanied by lateral depolarization of adatoms at higher coverage. As seen from appearance of plasmonic bands in EELS the metal clusters deposited on oxides acquire metallic character at coverage higher than 0.2 monolayers. There is also dramatic dependence of the deposited metal plasmon resonance intensity and its lifetime upon the atomic structure of the oxide support. For instance, plasmon intensity of Ag clusters of a mean size of about 30 nm on MgO(111) is as twice as higher than that on MgO(100). Additionally the plasmon resonance lifetime is higher in the former case. Thus, choosing atomic structure, morphology, relative content and nature of supported metal/oxide structures allows precise tuning of their electronic, catalytic and optical properties crucial for new technological applications. The work was supported by The Ministry of Education and Science of Russian Federation (Goszadanie SOGU) and Federal Target Program NCIMM (STU).The reported study was funded by RFBR according to projects # 16-52-50023-JaF, 16-02-00138-a. References 1. K. Honkala, Surface Sci. Reports 69 (2014) 366. 2. T.T. Magkoev, Solid State Commun. 132 (2004) 93.