Mechanical resonance of clamped silicon nanowires measured by optical interferometry

• Published in: Journal of applied physics 2008-04, Vol.103 (7)
• Main Authors: Belov, M., Quitoriano, N. J., Sharma, S., Hiebert, W. K., Kamins, T. I., Evoy, S.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2891002

The mechanical resonance of laterally grown silicon nanowires measured by an optical interferometric technique is reported. The lengths and diameters of the nanowires ranged from L=2to20μm and D=39to400nm, respectively. The wires showed resonant frequencies in the f0=1–12MHz range and resonant quality factors Q at low pressure ranging from Q=5000 to Q=25000. The dependence of resonant frequency on the ratio of diameter to length squared, D∕L2, yielded a ratio of E∕ρ=9400±450m∕s. Assuming a density of ρ=2330kg∕m3, this experimental result yields an experimental Young modulus of E=205±10GPa, consistent with that of a bulk silicon. As the wires were cooled from T=270KtoT=77K, a 0.35% increase of resonant frequency was observed. This increase of resonant frequency with cooling resulted from a change in Young’s modulus and from the thermal contraction of silicon. The quality factor did not vary significantly from P=10−4to102Torr, suggesting that viscous damping does not dominate the dissipative processes in this pressure range. Although viscous damping became important above P=102Torr, relatively high quality factors of Q=7000 were still observed at atmospheric pressure.