Itaru Yasui

Electrical and Structural Properties of Tin-Doped Indium Oxide Films Deposited by DC Sputtering at Room Temperature

Tin-doped indium oxide (ITO) films were deposited on soda-lime glass plates without substrate heating by dc magnetron sputtering. Crystallinity and electrical properties of the films were investigated by X-ray diffraction and Hall-effect measurements, which showed clear dependence on target–substrate distance (T–S) and on total gas pressure (Ptot) during deposition. Degradation in crystallinity was observed at relatively high or low Ptot, where the upper or lower Ptot level for depositing films with high crystallinity was increased with decreasing T–S. Based on a hard sphere collision model, the crystallinity of the films was considered to be strongly affected both by the kinetic energy of sputtered In (or Sn) particles and by the bombardment of high energy particles arriving at the growing film surface. The former could enhance the crystallinity, whereas the latter degraded both the crystallinity and conductivity. Such degradation in electrical properties was mainly due to a decrease in carrier density.

Study on Crystallinity of Tin-Doped Indium Oxide Films Deposited by DC Magnetron Sputtering

Tin-doped indium oxide (ITO) films were deposited by dc magnetron sputtering using oxide (ITO) or alloy (IT) targets. The ITO films sputter-deposited using Ar at total pressure (Ptot) lower than 1.2 Pa showed polycrystalline structure, whereas entirely amorphous films were deposited at Ptot higher than 1.4 Pa, indicating that the crystallinity of the ITO films were heavily affected by Ptot. This was quantitatively explained in terms of the kinetic energy of sputtered particles reaching to the substrate surface, which decreased due to an increase in collision frequency between the sputtered particles and sputtering gas molecules. ITO films were also deposited using Xe or He as sputtering gases, where amorphous films were deposited at Ptot higher than 0.7 Pa (Xe) and 12 Pa (He), respectively. Based on a hard sphere collision model, the energy loss rates of the sputtered particles due to collision with sputtering gas molecules were estimated to be consistent with the experimental results for the case of using He, Ar or Xe gases.

Preparation and Crystallization of Tin-doped and Undoped Amorphous Indium Oxide Films Deposited by Sputtering

Tin-doped and undoped amorphous indium oxide films were prepared by dc magnetron sputtering without substrate heating at relatively high total gas pressures and relatively large target-substrate distance. The structural and electrical properties of these films were investigated by X-ray diffraction and Hall-effect measurements. The amorphous tin-doped indium oxide (a-ITO) films were crystallized at a temperature about 30°C higher than that for amorphous indium oxide (a-IO) films.

X-ray diffraction study of microstructure of amorphous tungsten trioxide films prepared by electron beam vacuum evaporation

Microstructure of a-WO3 films prepared by electron beam vacuum evaporation was examined based on XRD. The peak positions in the observed PDFs corresponded with those in the PDFs calculated from the crystal structure of hexagonal WO3 and WO3 · 13H2O, and the framework structure of the films was therefore thought to consist of the basic structure of these crystals, three-, four-, and six-membered rings formed by WO6 octahedra. Microcluster models in which the atomic arrangement was similar to that of hexagonal WO3 were assumed and investigated in detail. The pair distribution functions calculated from these models showed good agreement with the observed values, and the structure of a-WO3 films was consequently suggested to consist of clusters in which the octahedra were arranged in the same manner as those in hexagonal WO3.

X-ray diffraction analysis on the structure of the glasses in the system PbOSiO2

Abstract The structures of PbO·SiO2 and 2PbO·SiO2 glasses have been analyzed by use of X-ray diffraction data and pair function method. For PbO·SiO2 glass, a model consisting of chains of PbO3 pyramids and silicate chains showed good agreement with the observed RDF. For 2PbO·SiO2 glass, the present authors reported previously a model in which chains of PbO3 pyramids are connected with SiO4 tetrahedra, while the chromatographic analyses of silicate anions by Gotz et al. and Smart et al. showed that silicate anions are distributed from monomer to polymer in the glass. We reexamined the structure of this glass referring to these results. Three representative models containing isolated SiO4, Si4O12 rings and (SiO3)n chains respectively as well as PbO3 chains were constructed and the RDFs were calculated with changing structure parameters. These three models showed satisfactory agreement with the observed data, showing that silicate anions are distributed from monomer to polymer in 2PbO·SiO2 glass and an increase of SiO2 content leads to polymerization of silicate anions to longer chains up to PbO·SiO2 composition, while the chains of PbO3 pyramids remain unchanged.

Electrical properties of heteroepitaxial grown tin‐doped indium oxide films

Oriented thin‐film tin‐doped indium oxide (ITO) was heteroepitaxially grown on optically polished (100) or (111) planes of single‐crystalline yttria‐stabilized zirconia (YSZ) substrates using e‐beam evaporation or dc magnetron sputtering techniques. Pole figure x‐ray diffraction analyses revealed that the heteroepitaxial relations were (001)ITO∥(001)YSZ, [100]ITO∥[100]YSZ, and (111)ITO∥(111)YSZ, [110]ITO∥[110]YSZ, respectively. X‐ray rocking curve analyses and Rutherford backscattering spectrometry revealed that the e‐beam evaporated heteroepitaxial ITO films had much higher crystallinity than the one deposited by dc magnetron sputtering. Both carrier density and Hall mobility of the e‐beam evaporated heteroepitaxial films showed steady increases in a wide temperature range, which could be interpreted in terms of the increasing Sn‐doping efficiency caused by the improvement of the crystallinity of In2O3 host lattice, and hence the decreasing Sn‐based neutral scattering centers.

Structural study of peroxopolytungstic acid prepared from metallic tungsten and hydrogen peroxide

Abstract The structure of peroxotungstic acid (W-PTA) prepared from metallic W and aqueous H 2 O 2 was investigated based on Raman, IR, and XRD analyses. W-PTA was an amorphous compound constructed of peroxo polytungstate anions, in which the anions were bound to each other through hydrogen bonding. RDF analyses suggested that the polyanion was W 12 O 38 (O 2 ) 16− 6 , in which a six-membered ring of corner-shared polyhedra, such as WO 5 (O 2 ) or WO 6 , was sandwiched by two W 3 O 10 units consisting of edge-shared WO 6 .

Oriented tin-doped indium oxide films on preferred oriented polycrystalline ZnO films

-oriented tin-doped indium oxide (ITO) films were deposited by rf magnetron sputtering on ZnO-coated glass substrates (ZnO/glass). The ZnO underlayers were also deposited by rf magnetron sputtering and have been known to exhibit preferred orientation in a wide range of deposition conditions. The X-ray diffraction profiles of the ITO films deposited on the ZnO/glass showed predominant orientation without any differently oriented crystallites, whereas the ITO films deposited on bare glass substrates (ITO/glass) under the same deposition conditions showed -preferred orientation with small areas of several other orientations. A mechanism of the heteroepitaxial growth of In2O3(111)|| ZnO(001) was explained by comparing the atomic configurations of oxygen between the oxygen mostly dense-packed planes of In2O3 and ZnO parallel to In2O3(111) and ZnO(001) planes, respectively. Sn concentrations and lattice constants of the -oriented films (ITO/ZnO/glass) were found to be greater than those of preferred oriented films (ITO/glass) in spite of the fact that the target and deposition conditions were the same, which could be associated with the electrical properties of the films.

DOPING MECHANISMS OF SN IN IN2O3 POWDER STUDIED USING 119SN MOSSBAUER SPECTROSCOPY AND X-RAY DIFFRACTION

The doping mechanism of Sn in In2O3 (ITO) powder was investigated using 119Sn transmission Mossbauer spectroscopy (TMS) and X-ray diffraction (XRD) in view of the chemical state of Sn. Deconvolution analyses of TMS spectra revealed that there was substitutional Sn4+ coordinated not only by 6 oxygen atoms [SnIn] but also by 7 or 8 oxygen atoms, for the samples with doping concentrations higher than 5 at.%. The amount of such electrically deactivated Sn4+ (coordination number of 7 or 8) increased with increasing doping concentration, which was quantitatively consistent with the decrease in doping efficiency. Precise XRD analyses indicated a systematic increase in the lattice constant with increasing doping concentration from 0.5 to 7 at.%. The increase in lattice constant was explained in terms of a repulsive force among tetravalent [SnIn] (coordination number of 6) with higher effective charge than In3+, which was also consistent with the results on the coordination of Sn4+ obtained through TMS analyses.

Structural study of amorphous WO3 thin films prepared by the ion exchange method

The structure of amorphous tungsten trioxide films was investigated with IR and Raman spectroscopic analyses and an XRD method. The films were prepared by ion exchange from sodium tungstate as a starting material. Films consisted of microclusters of 10–30 A diameter, in which the networks are formed with WO 6 octahedra sharing their corners and edges. The networks in the as-prepared samples consisted of WO 6 units with low symmetry, in which termination by W=O and W—OH 2 groups was common. As the post-annealed temperature became higher, the symmetry of WO 6 was improved and the edge-sharing octahedra disappeared.