AVS 53rd International Symposium
    Nanometer-scale Science and Technology Tuesday Sessions
       Session NS1-TuM

Paper NS1-TuM1
Electronic Transport in Nanometer-Scale Silicon Membranes

Tuesday, November 14, 2006, 8:00 am, Room 2016

Session: Nanoscale Structures and Characterization II
Presenter: P. Zhang, University of Wisconsin-Madison
Authors: P. Zhang, University of Wisconsin-Madison
E. Tevaarwerk, University of Wisconsin-Madison
B. Park, University of Wisconsin-Madison
D.E. Savage, University of Wisconsin-Madison
G. Celler, Soitec USA
I. Knezevic, University of Wisconsin-Madison
P. Evans, University of Wisconsin-Madison
M.A. Eriksson, University of Wisconsin-Madison
M.G. Lagally, University of Wisconsin-Madison
Correspondent: Click to Email
Use of silicon-on-insulator (SOI), a thin single-crystal silicon layer on silicon dioxide, is already pervasive in microelectronics. Additionally, SOI provides a potential new paradigm for surface studies, as these thin membranes become almost "all surface". For example, novel electronic properties emerge with decreasing membrane thickness, as surfaces and interfaces dominate bulk properties. We have investigated the conductivity of very thin (10nm) Si membranes bounded by one or two Si-SiO@sub 2@ interfaces. Below a certain thickness, free carriers in the membrane will be completely trapped by the oxide/Si interface states. For a typical doping level of 10@super 15@ cm@super -3@, the depletion thickness is of the order of 100 nm; in other words, a thin Si membrane bounded by two oxide layers will act like intrinsic Si. We demonstrate both experimentally and theoretically that the conductivity is vanishingly small for this case. Therefore scanning tunneling microscopy (STM) from thin membranes should be impossible. On the contrary, we successfully image 10 nm thick Si, when the top native oxide is removed and a clean reconstructed Si (001) surface exposed.@footnote 1@ We show that electronic conduction in a thin Si membrane is determined not by its "bulk" dopants but by the thermal excitation at 300K of Si valence band charges to the surface band. Bulk dopant concentration is virtually irrelevant for electronic properties of Si nanomembranes. Conductivity in the membrane can be tailored by modifying the surface chemistry. We predict that either electrons or holes can be thermally generated, depending on the exact positions of the HOMO and LUMO bands, relative to the Si nanomembrane conduction and valence bands edges, of molecules adsorbed on the surface of Si. The addition of such layers may provide a practical approach to manufacture nanoscale sensors with high sensitivity and reliability based on electronic readout. @FootnoteText@ @footnote 1@Pengpeng Zhang. et al. Nature 439, 703-706 (2006).