Tatsuya Saito

Phase-separated Al–Si thin films

Phase-separated Al–Si films composed of Al nanocylinders embedded in an amorphous-Si matrix have been prepared by a sputtering method. By controlling the deposition rate, substrate temperature, and film composition, the average diameter of the Al cylinders can be varied systematically from less than 5to13nm with a cylinder density ranging from 1015 to in excess of 1016cylindersm−2. A three-dimensional simulation of phase separation in binary thin films was performed using a modified Cahn-Hilliard [J. Chem. Phys. 28, 258 (1958)] equation to understand the growth mechanism. The simulation studies indicate that the surface diffusion length and film composition are important factors which determine film morphology. Experimental and simulation studies are compared and discussed.

Phase-Separated CsI-NaCl Scintillator With Optical Guiding Function

We demonstrate a new scintillator material that has a one-dimensional eutectic structure and optical light-guiding properties. Our light propagation calculations predicted that a structure where high refractive index luminescence cylinders are embedded in a matrix should show effective light-guiding properties. An inverse structure where a high refractive index luminescence matrix contains low refractive index cylinders was also predicted to possess light-guiding properties. A CsI-NaCl:Tl eutectic phase, which contained NaCl cylinders in a CsI matrix, was grown by a one-dimensional solidification method. This material showed high spatial resolution because of the difference in the refractive indices of NaCl and CsI.

Perpendicular recording media using phase-separated AlSi films

We have developed perpendicular recording media with nanosized cylindrical Co particles. The diameter and period of these particles are less than 10 and 12 nm, respectively. Al cylinders were grown in an a-Si matrix during AlSi film deposition due to the eutectic phase separation. The Al cylinders can be removed by chemical etching to form nanoporous templates. The pores were filled with Co by electrodeposition method via a metal underlayer as an electrode. These films show perpendicular anisotropy with Hc of 4.1 kOe.