| AVS 58th Annual International Symposium and Exhibition | |
| Electron Transport in Low Dimensional Materials Focus Topic | Tuesday Sessions |
| Session ET+EM+NS+GR-TuM |
| Session: | Electron Behaviors in Nanoelectronics, Interconnect, and Carbon-based Materials |
| Presenter: | Weina Peng, University of Wisconsin Madison |
| Authors: | W.N. Peng, University of Wisconsin Madison J. Endres, University of Wisconsin Madison S. Scott, University of Wisconsin Madison Z. Aksamija, University of Wisconsin Madison D.E. Savage, University of Wisconsin Madison I. Knezevic, University of Wisconsin Madison M.G. Lagally, University of Wisconsin Madison M. Eriksson, University of Wisconsin Madison |
| Correspondent: | Click to Email |
Silicon-on-insulator substrates provide large-area Si nanomembranes (SiNMs) mechanically supported by bulk handle wafers. Because of the intervening oxides, SiNMs are also electrically isolated from the substrates. The typical membrane thickness is less than a few hundred nanometers. Because they are so thin, SiNMs display interesting transport phenomena influenced by surface effects. Here, we demonstrate a novel method to probe surface transport via conductance measurements on SiNMs. When contacts are placed on the front surface, a current flows between the source and the drain via the membrane body as well as its surface. By utilizing an underlying back gate (the Si handle substrate), the conductance through the membrane can be continuously tuned and made smaller than the surface contribution, enabling experimental determination of the surface conductance. We measure the membrane conductance as a function of both the membrane thickness and the backgate voltage in ultra-high vacuum. In contrast to H-terminated Si surfaces, clean reconstructed Si(001)(2×1) surfaces show a constant-conductance regime when the backgate voltage is varied, and the conductance in this regime does not depend on membranes thickness. We demonstrate that the constant conductance (on the order of 10-9 Siemens) stems from an additional conduction channel through the dimer-reconstructed surface π* band. By comparing the experimental results to numerical simulations, the surface band mobility is determined to be in the range 10-50 cm2/Vs.
Research supported by NSF [UW MRSEC, award DMR-0520527, as well as awards 0937060 (subaward CIF-146) and ECCS-0547415] and DOE