アンジュレ一夕光源を使用した軟X線励起によるa-Si膜中のSi原子移動

摘要

アンジュレータ光源から発生した軟X線をa-Si膜（膜厚1，50nm）に照射したときの特性変化を検討した.照射前後で表面粗さRaは0.63nmから1.70nmへ変化した．これに対応して電気抵抗値も増加した．膜厚が薄い場合，単位原子当たりの光の吸収量が大きい．フォトンによるSi原子の振動励起がトリガーとなり，膜厚方向へ働く力が大きくなる．Si原子の移動が連続的に生じ凝集現象が起き，表面形状が変化したと考えられる．%We investigated the characteristics of a-Si film with thicknesses of 1 and 50 nm those were irradiated by soft X-ray from the undulator source. The average roughness Ra of lnm-thick-Si film were changed from 0.63 to 1.7nm by soft X-ray irradiation. The cohesion of Si atoms were observed. The electric resistivity of it also increased corresponding to the change of the surface roughness. The X-ray absorption rate of thin Si film becomes larger than the thick film. Because the phonon excitation of Si atoms by X-ray absorption becomes remarkable, the perpendicular force worked to Si atoms increases. This causes the cohesion of Si atoms at the surface.