In 2 O 3 Based Multicomponent Oxide Transparent Conducting Films Prepared by R.F. Magnetron Sputtering
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using various multicomponent oxides consisting of a combination of different In 20 3 based ternary compounds. (Gajn)20 3 -Mgln 2O4, (Gajln) 20 3-Zn 2 In2O5, (Galn) 203-On4Sn3(O 2, Zn 2ln 205-In4 Sn 30 2 and Zn 2 ln205 MgIn 20 4 system thin films have been prepared. EXPERIMENTAL Films were prepared by conventional r.f. planar magnetron sputtering using powder targets. A mixture of ZnO (purity, 99.99%), MgO (purity, 99.99%), In 20 3 (purity, 99.99%), Ga203 (purity, 99.99%) and Sn0 2 (purity, 99.99%) powders calcined at 1000"C in an argon (Ar) atmosphere for 5 hours was used as the target: stainless steel holder, diameter of 80 mm. Substrates of Corning 7059 glass were placed parallel to the target surface at a distance of 35 mm. Sputtering deposition was carried out at sputter gas pressures of 0.2 to 2.0 Pa in a pure Ar gas or a mixture of Ar and oxygen (02) gases with a d.c. power of 40 W. The 02 gas content in the Ar+0 2 gas atmosphere was varied from 0 to 8%. Substrate temperatures were room temperature (RT). Although substrates at RT were not intentionally heated, surface temperatures reached about 160C after a sputter deposition of approximately 30 min. The deposition rate was dependent on the powder composition; the deposition rates for ZnO, MgO, In 20 3, Ga 20 3 and Sn0 2 powders were about 15, 10, 10, 8, 8 nm/min, respectively. Film thickness was measured using a conventional surface roughness detector with stylus. The thickness of films deposited in this work ranged from 340 to 490 nm. The composition of deposited films was measured by energy dispersive X-ray spectroscopy (EDX). The EDX of the deposited multicomponent oxide films showed that the composition (the metal element content, or the atomic ratio) in the films was approximately equal to that in the target. The crystalline structure of the deposited films was investigated by X-ray diffraction, a conventional X-ray unit with a copper anode was used. Electrical resistivity and Hall mobility were measured using the van der Pauw method. Optical transmission through the film was measured in the visible wavelength range, 300 to 800 nm. The work function of the films was determined from the wavelength dependence of photoemission of electrons using ultraviolet photoelectron spectroscopy (Model AC-1 Riken Keiki Co. Ltd.). RESULTS AND DISCUSSION Transparent conducting Mgln 2O 4 and In 4Sn 30 1 2 films prepared on substrates at RT by r.f. magnetron sputtering were always polycrystalline.[2,16] In contrast, (Ga,ln) 20 3 and Zn 21n20 5 films prepared on RT substrates were amorphous;[10-13] however, these films prepared on substrates at 350°C were polycrystalline,[10-131 identified as (Ga,In) 20 3 and Zn 2 1n2O5, respectively. Therefore, in the following description, the formula of the above materials are presented as ternary compounds even for materials where the films prepared at RT are amorphous. (GaInQhS-In 4 SnO• 2 Thin Films We reported that transparent conducting In4Sn3O 12 films were prepared at substrate temperatures of RT and 3509C by r.f. or d.c. magnetr
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