封面图片 2013年, 第8卷 第1期
The electric transport properties of low-dimensional systems have attracted tremendous interests due to their applications in microelectronics and novel nanodevices. Ultra-thin metal films on semiconductor substrates have been a playground for the study of electronic transport properties of low dimensional materials. However, the experimental measurements on the electric transport of such systems are still challenging since they only survive in UHV environments due to high chemical activity. Besides, surface-sensitive methods are required to avoid the substrate effects that could be coupled with the transport of the metal systems atop. We develop the micro-four-point-probe method integrated with standard low-temperature scanning tunneling microscope, which allows the vibration-proof environments and a broad temperature range (4-300 K) for transport measurements. Both the high-resolution characterizations of the surface structure and in situ measurements of the electric transport are realized in a broad temperature range. Taking the Ag/Si(111)-(√3×√3)R30o interface as the prototype of two-dimensional metals, the metal-insulator transition is studied in detail. The surface structure characterizations show hexagonal patterns at room temperature, which supports the model of inequivalent triangle structure. A metal-insulator transition occurs at ~115 K. The low temperature transport measurements clearly reveal the strong localization characteristics of the insulating phase. For more detailed information, please refer to the article “Strong localization across the metal-insulator transition at the Ag/Si(111)-(√3 ×√3)R30o interface” by Yuan-Yuan Tang and Jian-Dong Guo, pp 44–49. [Photo credits: Jian-Dong Guo, Institute of Physics, CAS][展开] ...