Jul 15, 2015 - b Voronezh State Technical University, Department of Semiconductor Electronics and Nanoelectronics, Moscow av., 14, 394026 Voronezh, ...
Journal of the European Ceramic Society 35 (2015) 3885–3892
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Synthesis of Zn2 SnO4 powders via hydrothermal method for ceramic targets I˙ .G. Tuncolu a , C. Aciksari a , E. Suvaci a , E. Ozel a,∗ , S.I. Rembeza b , E.S. Rembeza b , E.Yu. Plotnikova b , N.N. Kosheleva b , T.V. Svistova b a b
Anadolu University, Department of Materials Science and Engineering, Iki Eylul Campus, 26480 Eskisehir, Turkey Voronezh State Technical University, Department of Semiconductor Electronics and Nanoelectronics, Moscow av., 14, 394026 Voronezh, Russia
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Article history: Received 31 March 2015 Received in revised form 30 June 2015 Accepted 2 July 2015 Available online 15 July 2015 Keywords: Chemical preparation Hydrothermal synthesis Zinc stannate (Zn2 SnO4 )
a b s t r a c t The preparation of (SnO2 )x (ZnO)1−x powder as a ceramic target material via hydrothermal synthesis within a broad range of x values (x = 0–1) was investigated. The phase development and particle characteristics of the Zn2 SnO4 powders were evaluated. The phase formations of the (SnO2 )x (ZnO)1−x system in the range from x = 0.0 to 1.00 were mapped, and the ZnO, SnO2 and Zn2 SnO4 phases were found to depend on the changing x value. The effects of the processing parameters, including the treatment temperature (180–220 ◦ C), time (0–24 h) and initial concentrations of precursors (Sn:Zn = 0.125:0.3, 0.2:0.48, 0.25:0.6, 0.35:0.84, 0.5:1.20), on the formation mechanism of Zn2 SnO4 were discussed in detail. Almost single phase Zn2 SnO4 occurs only when x = 0.29 (Zn/Sn = 2.4:1) for the (SnO2 )x (ZnO)1−x composite system at 220 ◦ C for 24 h. The results reveal that the target prepared from synthesized Zn2 SnO4 powder can be successfully used to develop thin film transistor channels. © 2015 Elsevier Ltd. All rights reserved.
1. Introduction Zinc stannate (ZTO) composite powder is a candidate target material that can be used in a wide variety of applications, such as gas and humidity sensors, transparent thin film transistors (TTFT) [1], transparent conductive electrodes, functional coating and as negative electrodes for Li-ion batteries [2]. ZTO is an n-type ternary oxide semiconductor (II–IV–VI) that has unique properties, including high electron mobility, high electrical conductivity, low visible absorption and excellent optical properties [3]. In a zinc oxide–tin dioxide system, two compounds, namely, zincorthostannate (Zn2 SnO4 ) and zinc metastannate (ZnSnO3 ), are reported to form [4]. Data from the literature indicates that ZnSnO3 is stable only at low temperatures (92% of theoretical density. After sintering, Zn2 SnO4 target consists of Zn2 SnO4 phase. After sputtering, the thickness of the films on the silicon was measured by an LEF-753 ellipsometer as 2 m, and the transparency of the films on the glass was approximately 20%. The composition of all films deposited by two methods is the same. XRD data show that all films contained Zn2 SnO4 phase and traces of SnO2 and ZnO phases. Interestingly, it was found that the electrical properties of the films deposited from the targets containing commercial and hydrothermal synthesized powders are different. The concentration of the electrons (n) in films prepared from commercial powders was approximately 2.0.1017 cm−3 , and mobility of free carriers ()
Fig. 14. SEM images of (a) the hydrothermal synthesized Zn2 SnO4 powder prepared with x = 0.29 at 220 ◦ C and (b) polished, thermally etched cross-section of the Zn2 SnO4 target sintered at 1200 ◦ C for 2 h.
Fig. 13. Schematic illustration of formation of the Zn2 SnO4 changing with initial concentration of precursors. (For interpretation of the references to color in the text, the reader is referred to the web version of this article.)
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was ∼12 cm−2 /V.s. The concentration of the electrons in the films prepared from the Zn2 SnO4 target was 3.0. 1018 cm−3 , and mobility of free carriers was 15 cm−2 /V. s. These results show that in the films deposited from the Zn2 SnO4 target, the concentration of electrons is roughly one order of magnitude higher than in the commercial films, and the mobility of free carriers is nearly the same in both samples. The difference in the concentration of electrons is attributed to the presence of different impurities (as found by X-ray microanalysis) and various defects in the commercial powders. As the materials for the fabrication of ceramic targets, we used specially purified commercial SnO2 and ZnO powders with a purity of higher than 99.9%. The initial chemically pure commercial powders contained mainly Fe2 O3 , Na2 O, and SiO2 impurities (according to the data of X-ray analysis). However, after repeated washing of the powders in distilled water at a temperature of 90 ◦ C, it was possible to remove almost all oxides except iron oxide, reducing its mass content to
