坂間 弘

The structures of Ga-adsorbed Si(110) surfaces were studied by means of QMS, AES and LEED. There exist three adsorption phases (alpha, beta, gamma), two of which are two-dimensional phases (alpha, beta). The saturation coverage of the alpha, beta phase is 0.11 and 0.17, respectively. The unit cell of surface structure "A" which corresponds to the alpha phase is 9 times larger than that of the bulk structure and the unit cell of structure "B" for the beta phase is 12 times larger. The "A" structure is observed at a substrate temperature of 800 < T(s) < 870 K, while "B" is observed at 755 < T(s) < 800 K.

The structure of the Si(111)Š3 × Š3 -Ga surface has been studied by dynamic analysis of low-energy electron-diffraction curves of intensity versus energy (I-V). It has been found that a structure in which Ga atoms are located on the second layer of Si atoms well explains the experimentally obtained I-V curves. In this geometry, a large deformation of the surface layer results from the stable adsorption of Ga atoms. The optimum configuration is close to that proposed by Northrup in his study of the Si(111)Š3 × Š3 -Al surface. © 1988 The American Physical Society.