Morphology and Structure of Defected Niobium Oxide Nonuniform Arrays Formed by Anodizing Bilayer Al/Nb Systems
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ICAL SCIENCE OF MATERIALS
Morphology and Structure of Defected Niobium Oxide Nonuniform Arrays Formed by Anodizing Bilayer Al/Nb Systems A. Pligovkaa,*, P. Yuninb, A. Hohaa, S. Korolyovb, G. Gorokha, and E. Skorokhodovb aResearch
and Development Laboratory 4.10 “Nanotechnologies,” Belarusian State University of Informatics and Radioelectronics, Minsk, 220013 The Republic of Belarus b Institute for Physics of Microstructures, Russian Academy of Sciences, Nizhny Novgorod, 603087 Russia *e-mail: [email protected] Received April 28, 2020; revised April 28, 2020; accepted April 28, 2020
Abstract—The work is devoted to the X-ray diffraction research of defected niobium oxide nonuniform (NON) arrays and niobium oxide nanocolumns formed by electrochemical anodizing. The obtained results allow to make an assumption about the probable presence of a significant amount of NbO, NbO0.7, Nb2O5 and a small amount of NbO2, and Al in the composition of defected NON and the presence of all these substances in the nanocolumns of niobium oxide except NbO0.7, but in smaller quantities. The comparative analysis of the NON structure and the nanocolumns makes it possible to isolate, probably, a significant amount of Nb0.94O0.06, Nb6O in the defected nanocolumns, which was not found in NON. DOI: 10.1134/S1063784220110213
INTRODUCTION The research of electrochemical anodic oxidation (anodizing) processes of valve metals through anodic aluminum oxide (AAO) pores is very relevant, since anodizing allows creating arrays of uniformly hexagonal close-packed nanostructured oxide nonuniform arrays, whose morphology, composition and physical properties can be controlled by changing the anodizing modes [1–5]. Reanodizing of such nonuniform arrays leads to the formation of full niobium oxide nanocolumns [6]. Similar arrays of nanocolumns can also be formed from the anodic oxide of tantalum, hafnium and tungsten [7–9]. The investigations have shown [10] that niobium oxide nonuniformities (NON) have different morphology, in contrast, for example, to the nonuniformities of tantalum oxide, which have the same spherical shape in all previously established anodizing modes [2]. From the work [11] it can be observed that the NONs differ not only in size, but also in the shape and the nature of their arrangement. The main works [2, 6] on this topic are devoted to the research of the morphology and composition of niobium oxide nanocolumns, while the composition of the NON themselves is little investigated. The results of the NON research by X-ray photoelectron spectroscopy (XPS) are presented in [11]. The NON was formed by anodizing in 0.8 M aqueous tartaric acid solution at a forming voltage 200 V. The shape of such NON was cup-shaped, which is typical for this mode [10]. The research showed the presence of Nb, O, Al, and C in the composition of the investi-
gated formations. Deep profiling was determined by the peaks of Nb 3d, Al 2p, O 1s, and C 1s. The carbon peak disappeared immediately after the beginning of Ar+ sputtering, indicating that carbon-contai
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