Quasi-Ordered Nano-Sized Structure on Surface of Oxide Crystals
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0961-O15-09
Quasi-Ordered Nano-Sized Structure on Surface of Oxide Crystals Ivan Doichinovic1, Jablan Dojcilovic2, Dusan Popovic2, Jagos Puric3, and Nicolay Alex Kulagin4 1 Physics, University of Belgrade, Studentski trg. 11, Belgrade, 11000, Yugoslavia 2 Physics, University of Belgrade, Studentski trg. 12, Belgrade, 11000, Yugoslavia 3 Center of Science and Technology Development, Belgrade, 11000, Yugoslavia 4 Physics Department, Kharkov NAtional University for Radioelectronics, Shakespeare, 6-48, Kharkov, 61045, Ukraine ABSTRACT An article is given of research of SEM and optic data of surface of pure and doped SrTiO3 single crystals before and after plasma treatment. Quasi-ordered system of nano-scaled size triangle pyramids was discovered for separate doped samples. PACS: 42.70-a, 74.25 Gz, 76.30Fc, 78.00.00 Key words: perovskite, nano-structure, plasma-enhanced CVD, SEM, optic INTRODUCTION Interest to study pure and doped perovskite crystals, such as, SrTiO3 is stable for a long time [1-4] and raised after discovery of high temperature superconductivity [5]. Last time interest to nanoclusters and nano-scaled size samples and study of surface after treatment and irradiation arises, too [6-8]. High value of refractive index: n = 2.4 (similar one to the diamond), non-linear optical properties and gigantic electroluminescence studied for separate pure and doped samples came to expansion of employment of perovskites. Using experimental data performed by separate scientists several phase transitions, PT, when T = 10, 30, 65 and 105 K were studied for SrTiO3 [1-4, 9-11]. It is well known that the structural PT under Tc = (105 ± 2) K is a displacement-type PT and below Tc the symmetry of crystalline lattice of the strontium titanate changes from cubic to tetrahedral one. Parameter of crystalline lattice for separate samples varies from a = 3.9051 A to a = 3.9102 A [11]. Dielectric constant, ε0 changes too, from 50 to 360 units [10]. For separate single crystals the photochromism, dichroism and other anomalous properties of the cubic crystals were studied, earlier [12-15].Detail investigation of the crystalline structure of SrTiO3 reveals the distortions of perovskite structure above and below Tc [1617]. Modification of stoichiometry, certain change of the growth technology, and related transition of some part of Ti+4 ions into Ti+3 oxidation state are the causes of change of the dielectrical, optical and other properties of Sr+2Ti+4O-23. Results of investigation of the oxidation state of Ti+n ions in pure and doped strontium titanate grown by different methods were presented in papers [18-19]. Investigation of the oxidation state of Ti ions in SrTiO3 and TixOy single crystals shows that more than 20 % of titanium ions may change valency in the samples [19]. It should be noticed a variation of the Sr/Ti relation for pure and doped samples was discovered for separate SrTiO3 single crystals. Stoichiometry varies at 5-20 % for the pure and doped samples.
Separate pecularities of the optical properties of SrTiO3 were stud
