Electronic transport properties of surface-state bands on semiconductors

1 .我们已经开发了一个RHEED sample holder for surface conductivity measurements at lowtemperatures in ultrahigh vacuum，and installed it in a UHV-RHEED chamber with a superconducting magnet to measure Hall effect andmagnetoresistance.(2) Temperature dependence of surface conductivity of Si(111)- D83 d8xD83 D8- ag和D821 D8 X D821 D8- ag surfaces was measured in a range of 40 to 300k . in atemperature range of 100 to 300k，the conductivity of the 7 X 7 was d8x d8x D8 was the highest while that of the 7 X 7 was thelowest. The conductivity of The agcovered surfaces increased with temperature lowering，meaning a metallic conductivity. Below 100k，7 X 7 surface showed the highest conductivity.(3) Magnetoresistance of Bi atomic layers onSi(111) surface was measured under a magnetic field up to 6 T at room temperature. The resistancechanged by a few %.(4) D83 D8 surface superstructure induced by 1/3 monolayer Snadsorption on Si(111) surface was found to show a phase transition into a 3 X 3 phase by coolingdown to around 100k . This may be a charge-density wave transitionsimilar to that observed on Sn-covered Ge(111) surface。

(1) We have developed an RHEED sample holder for surface conductivity measurements at low temperatures in ultrahigh vacuum, and installed it in a UHV-RHEED chamber with a superconducting magnet to measure Hall effect and magnetoresistance.(2) Temperature dependence of surface conductivity of Si(111)-ィイD83ィエD8 X ィイD83ィエD8-Ag and ィイD821ィエD8 X ィイD821ィエD8-Ag surfaces was measured in a range of 40 to 300 K. In a temperature range of 100 to 300K, the conductivity of the ィイD821ィエD8 X ィイD821ィエD8 was the highest while that of the 7 X 7 was the lowest. The conductivity of the Ag-covered surfaces increased with temperature lowering, meaning a metallic conductivity. Below 100K, the 7 X 7 surface showed the highest conductivity.(3) Magnetoresistance of Bi atomic layers on Si(111) surface was measured under a magnetic field up to 6 T at room temperature. The resistance changed by a few %.(4) A ィイD83ィエD8 X ィイD83ィエD8 surface superstructure induced by 1/3 monolayer Sn adsorption on Si(111) surface was found to show a phase transition into a 3 X 3 phase by cooling down to around 100 K. This may be a charge-density wave transition, similar to that observed on Sn-covered Ge(111) surface.