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Reports
Submitted on November 11, 2002 Small-Diameter Silicon Nanowire Surfaces
1 Center of Super-Diamond and Materials Science & Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, China. * To whom correspondence should be addressed. E-mail: apannale{at}cityu.edu.hk. Small diameter (1-7 nanometers) silicon nanowires (SiNW) were prepared, and their surfaces were removed of oxide and terminated with hydrogen by a hydrofluoric acid dip. Scanning tunneling microscopy (STM) of these SiNWs, performed both in air and in ultra high vacuum, revealed atomically resolved images that can be interpreted as hydrogen-terminated Si (111)-(1x1) and Si (001)-(1x1) surfaces corresponding to SiH3 on Si(111) and SiH2 on Si(001) respectively. These H-terminated SiNW surfaces seem to be more oxidation resistant than regular silicon wafer surfaces, since atomically resolved STM images of SiNWs were obtained in air after several days exposure to ambient environment. Scanning tunneling spectroscopy measurements were performed on the oxide-removed SiNWs, and used to evaluate the electronic energy gaps. The energy gaps were found to increase with decreasing SiNW diameter from 1.1 eV for 7 nanometers to 3.5 eV for 1.3 nanometers, in agreement with previous theoretical predictions.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)
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