Gallium structure on the Si(111)-(7 × 7) surface: influence of Ga coverage and temperature

Abstract

The results of gallium deposition on the Si(111)-(7 × 7) surface at different substrate temperatures (−183, RT, 300, 490 and 530 ◦ C) as well as the influence of subsequent annealing of the prepared layers are presented. The gallium structure was monitored by low-energy electron diffraction (LEED) and synchrotron radiation photoelectron spectroscopy (SR-PES). A detailed analysis of photoelectron spectra was carried out and three different Ga 3d peak components recognized—the first one was related to the ( √ 3 × √ 3) R30 ◦ reconstruction, the second to gallium island bases, and the third one to metallic gallium deposited on these bases. Depending on substrate temperature either only the island bases were formed (over 490 ◦ C) or these bases were covered with extra gallium atoms in an additional layer (300 ◦ C). In the case of room (low) temperature deposition only a weak interaction of gallium with the (7 × 7) substrate and a non-ordered growth were found. If the gallium coverage exceeded a critical value the gallium formed small droplets on the silicon surface. Annealing of the deposited layers showed differences between the second and the third gallium layer. In addition to previously reported structures a new (3 √ 3 × 3 √ 3) R30 ◦ reconstruction was observed after high temperature deposition followed by annealing to 530 ◦ C. This structure was stable in a narrow temperature range and forms an intermediate step between the ( √ 3 × √ 3) R30 ◦ reconstruction and the island structure.