AVS 52nd International Symposium
    Surface Science Friday Sessions
       Session SS2-FrM

Paper SS2-FrM8
Surface Electronic Transport in Ultrathin Silicon-on-Insulator

Friday, November 4, 2005, 10:40 am, Room 203

Session: Electronic Structure of Surfaces
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. 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
Silicon-on-insulator (SOI), a thin single-crystal silicon template layer on silicon dioxide, promises to become the platform for future high-speed electronics, as well as for a range of sensor technologies. When the Si layer is very thin, unique phenomena arise. The emergence of novel electronic properties with decreasing Si template layer thickness is particularly important. In contrast to the conventional view, ultrathin SOI displays rich electronic phenomena. It is usually claimed that STM imaging of thin SOI is impossible, because a thin SOI layer is fully depleted of free carriers (and thus overly resistive), which in effect eliminates the current path from the STM electrode tip to the contact. In complete contrast to this view, we report successful STM imaging of ultrathin (10 nm) SOI, when the top native oxide is removed and a clean reconstructed Si (001) surface is exposed.@footnote 1@ We explain theoretically the low sheet resistance of ultrathin SOI that has a reconstructed-Si [(2x1)] surface. We attribute the ability to image to surface electronic transport. The presence of a high density of states in surface bands (pi and pi*) and the position of the narrow surface bandgap are the dominant mechanisms in repositioning the Fermi level in ultrathin SOI. They lead to a high density of free carriers. The bulk doping density and the density of interface states on the back Si/SiO@sub 2@ interface are largely irrelevant for electronic properties of ultrathin SOI with a clean reconstructed surface. We confirm this conclusion with sheet resistance measurements on SOI covered with thin oxide. The influence of hydrogen on conductivity in ultra-thin SOI will also be discussed. Our measurements suggest that it will be possible to follow thin-Si-membrane structure and properties continuously from bulk to the ultimate limit of a Si film one unit cell high on oxide. Research supported by NSF, AFOSR, and DOE. @FootnoteText@ @footnote 1@Pengpeng Zhang, et al., submitted.