Shizutoshi Ando

Use of diethylselenide as a less-hazardous source for preparation of CuInSe2 thin films by selenization of metal precursors

Abstract A less-hazardous and low cost selenization method for the preparation of CuInSe 2 films was demonstrated using diethylselenide [(C 2 H 5 ) 2 Se:DESe] as a Se source alternative to H 2 Se. By using N 2 as a carrier gas, potential H 2 leakage risk was removed from our previous work [J. Cryst. Growth 243 (2002) 404]. The structural and optical properties of CuInSe 2 films fabricated by this method were found to be almost equal to those of the films prepared by the selenization process using DESe/H 2 system.

Direct Observation of an Ordered Phase in (1120) Plane InGaN Alloy

A polar-dependent phase with spontaneous atomic ordering is found in a nonpolar (1120) plane In0.08Ga0.92N film grown by metalorganic vapor-phase epitaxy. An atomic arrangement is a periodic sequence of group-III sublattices, such as In0.04Ga0.96N/In0.12Ga0.88N, that is only observed in a nitrogen polar region through systematic transmission electron microscopy investigation. Cathodoluminescence (CL) in the nitrogen polar region, i.e., spontaneously ordered atomic structure of InGaN, reveals anomalous emission behavior, specifically an S-shape-like (increase–decrease) temperature dependence of CL peak energy. It is suggested that the spontaneous ordered atomic structure of InGaN plays the role of a localized center owing to band gap shrinkage, which has been reported in other III–V alloy systems.

Preparation and characterization of ZnS thin films by the chemical bath deposition method (Conference Presentation)

Nowadays, the conversion efficiency of Cu(In･Ga)Se2 (CIGS)-based solar cell already reached over 20%. CdS thin films prepared by chemical bath deposition (CBD) method are used for CIGS-based thin film solar cells as the buffer layer. Over the past several years, a considerable number of studies have been conducted on ZnS buffer layer prepared by CBD in order to improve in conversion efficiency of CIGS-based solar cells. In addition, application to CIGS-based solar cell of ZnS buffer layer is expected as an eco-friendly solar cell by cadmium-free. However, it was found that ZnS thin films prepared by CBD included ZnO or Zn(OH)2 as different phase [1]. Nakata et. al reported that the conversion efficiency of CIGS-based solar cell using ZnS buffer layer (CBD-ZnS/CIGS) reached over 18% [2]. The problem which we have to consider next is improvement in crystallinity of ZnS thin films prepared by CBD. In this work, we prepared ZnS thin films on quarts (Si02) and SnO2/glass substrates by CBD with the self-catalysis growth process in order to improve crystallinity and quality of CBD-ZnS thin films. The solution to use for CBD were prepared by mixture of 0.2M ZnI2 or ZnSO4, 0.6M (NH2)2CS and 8.0M NH3 aq. In the first, we prepared the particles of ZnS on Si02 or SnO2/glass substrates by CBD at 80℃ for 20 min as initial nucleus (1st step ). After that, the particles of ZnS on Si02 or SnO2/glass substrates grew up to be ZnS thin films by CBD method at 80℃ for 40 min again (2nd step). We found that the surface of ZnS thin films by CBD with the self-catalyst growth process was flat and smooth. Consequently, we concluded that the CBD technique with self-catalyst growth process in order to prepare the particles of ZnS as initial nucleus layer was useful for improvement of crystallinity of ZnS thin films on SnO2/glass. [1] J.Vidal et,al., Thin Solid Films 419 (2002) 118. [2] T.Nakata et.al., Jpn. J. Appl. Phys. 41(2B), L165-L167 (2002)

Evaluation of Correlation Between Orientation of Y 3 Fe 5 O 12 (YIG) Thin Film and Spin Seebeck Effect

We found that the orientation of the magnetic material yttrium–iron–garnet (YIG) depends on the type of substrate. The orientation of YIG was evaluated using an orientation index. We obtained experimental results suggesting that the orientation of YIG is related to the saturation value of the generated voltage by the spin Seebeck effect and the diffusion length of the spin current. The diffusion length of the spin current is proportional to the orientation index.