Transport characteristics of single crystal bismuth films on Si（111）-7×7 are found to be metallic or insulating at temperature below or above Tc, respectively. The transition temperature Tc decreases as the fil...Transport characteristics of single crystal bismuth films on Si（111）-7×7 are found to be metallic or insulating at temperature below or above Tc, respectively. The transition temperature Tc decreases as the film thickness increases. By combining thickness dependence of the films resistivity, we find the insulating behaviour results from the states inside film, while the metallic behaviour originates from the interface states. We show that quantum size effect in a Bi film, such as the semimetal-to-semiconductor transition, is only observable at a temperature higher than Tc.展开更多
The magneto-transport properties of thin single crystal Bi films epitaxial grown on Si(111)-7×7 surfaces are investigated systematically as functions of film thickness(5–55 nm)and temperature.Under a perpendicul...The magneto-transport properties of thin single crystal Bi films epitaxial grown on Si(111)-7×7 surfaces are investigated systematically as functions of film thickness(5–55 nm)and temperature.Under a perpendicular magnetic field,the positive magnetoresistance(PMR)effect is normally found,and its curve shapes are evolved systematically with film thickness.In contrast,under parallel magnetic fields the PMR effect observed for thinner Bi films develops into the negative magnetoresistance effect with the increasing magnetic field for the thicker Bi film.Our analysis indicates that there exists strong competition between the weak anti-localization effect in the surface states and the weak-localization effect in the bulk states of the Bi film,which induces the anomalous changes in the parallel magneto-resistance curves.The temperature-dependent experiments further demonstrate that the surface state plays an important role in the magneto-transport process of Bi films.展开更多
Anomalous transport properties of 40-nm-thick single-crystal Bi（111） films grown on Si（111）-7 × 7 substrates is investigated. The magnetoresistance （MR） of the films in perpendicular magnetic field shows a ...Anomalous transport properties of 40-nm-thick single-crystal Bi（111） films grown on Si（111）-7 × 7 substrates is investigated. The magnetoresistance （MR） of the films in perpendicular magnetic field shows a regular positive behavior in the temperature range 2–300K, the MR in parallel field （B｜｜） displays a series of interesting features. Specifically, we observe a change of the MR （B｜｜） behavior from positive to negative when the temperature is below 10K. In the range 10–170 K, the MR （B｜｜） is negative in the investigated field of 9T. When T 〉 170 K, a positive MR appears in the high field regime. The low temperature MR（B｜｜） behavior in the parallel field can be understood by the competition between weak localization and weak anti-localization （WAL）. Furthermore, our results suggest that the WAL is dominated by the interface carriers.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10874217 and 10427402)the National Basic Research Program of China(973 Program)(Grant No.2006CB933000)
文摘Transport characteristics of single crystal bismuth films on Si（111）-7×7 are found to be metallic or insulating at temperature below or above Tc, respectively. The transition temperature Tc decreases as the film thickness increases. By combining thickness dependence of the films resistivity, we find the insulating behaviour results from the states inside film, while the metallic behaviour originates from the interface states. We show that quantum size effect in a Bi film, such as the semimetal-to-semiconductor transition, is only observable at a temperature higher than Tc.
基金Supported by the National Basic Research Program of China under Grant No 2009CB930803the National Natural Science Foundation of China under Grant No 10834012the Knowledge Innovation Project of the Chinese Academy of Sciences under Grant No KJCX2-YW-W24.
文摘The magneto-transport properties of thin single crystal Bi films epitaxial grown on Si(111)-7×7 surfaces are investigated systematically as functions of film thickness(5–55 nm)and temperature.Under a perpendicular magnetic field,the positive magnetoresistance(PMR)effect is normally found,and its curve shapes are evolved systematically with film thickness.In contrast,under parallel magnetic fields the PMR effect observed for thinner Bi films develops into the negative magnetoresistance effect with the increasing magnetic field for the thicker Bi film.Our analysis indicates that there exists strong competition between the weak anti-localization effect in the surface states and the weak-localization effect in the bulk states of the Bi film,which induces the anomalous changes in the parallel magneto-resistance curves.The temperature-dependent experiments further demonstrate that the surface state plays an important role in the magneto-transport process of Bi films.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10874217 and 10427402, and the National Basic Research Program of China under Grant No 2006CB933000.
文摘Anomalous transport properties of 40-nm-thick single-crystal Bi（111） films grown on Si（111）-7 × 7 substrates is investigated. The magnetoresistance （MR） of the films in perpendicular magnetic field shows a regular positive behavior in the temperature range 2–300K, the MR in parallel field （B｜｜） displays a series of interesting features. Specifically, we observe a change of the MR （B｜｜） behavior from positive to negative when the temperature is below 10K. In the range 10–170 K, the MR （B｜｜） is negative in the investigated field of 9T. When T 〉 170 K, a positive MR appears in the high field regime. The low temperature MR（B｜｜） behavior in the parallel field can be understood by the competition between weak localization and weak anti-localization （WAL）. Furthermore, our results suggest that the WAL is dominated by the interface carriers.
