Small-Diameter Silicon Nanowire Surfaces
D. D. D. Ma,
C. S. Lee,
F. C. K. Au,
S. Y. Tong,
S. T. Lee*
Small-diameter (1 to 7 nanometers) silicon nanowires
(SiNWs) 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 ultrahigh
vacuum, revealed atomically resolved images that can be interpreted as hydrogen-terminated Si (111)-(1 × 1) and Si (001)-(1 × 1)
surfaces corresponding to SiH3 on Si (111) and
SiH2 on Si (001), respectively. These hydrogen-terminated
SiNW surfaces seem to be more oxidation-resistant than regular silicon
wafer surfaces, because atomically resolved STM images of SiNWs were
obtained in air after several days' exposure to the ambient
environment. Scanning tunneling spectroscopy measurements were
performed on the oxide-removed SiNWs and were used to evaluate the
electronic energy gaps. The energy gaps were found to increase with
decreasing SiNW diameter from 1.1 electron volts for 7 nanometers to
3.5 electron volts for 1.3 nanometers, in agreement with previous theoretical predictions.
Center of Super-Diamond and Advanced Films and 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
