Xe/Ag (111) の層成長における構造変化
2000 年 43 巻 4 号 p. 492-498
詳細
2000 年 43 巻 4 号 p. 492-498
The layering transition of a physisorption system on a metal single crystal has been investigated by means of an ellipsometry and an eXtremely-low-current LEED (XLEED). Our XLEED system is operated at the primary electron current of about 0.1 pA, which minimizes the effect of desorption, defect formation, and charging. We observed the surface structure of Xe/Ag (111) by XLEED while monitoring the layer growth by the ellipsometry from a submonolayer film to a thick one. An equilibrium between the Xe film and coexisting three-dimensional Xe gas has been maintained throughout the experiment. From a monolayer film to a sufficiently thick film, the Xe overlayer has clear hexagonal structure whose directions of the unit vectors are coincident with those of the substrate. The Xe-Xe spacing in the monolayer film on Ag (111) is known to be a few per cent larger than that of bulk. Our interest is how the Xe-Xe spacing varies in the process of layer growth. We have made a systematic observation of the change of the Xe-Xe spacing in one and two monolayer films at pressures between 10-7 and 10-2 Pa and at temperatures between 50 and 100 K.
