Surface effects and high quality factors in ultrathin single-crystal silicon cantilevers

Surface effects in ultrathin single-crystal silicon cantilevers of 170 nm thickness, which are optically actuated mainly by the light pressure effect, are investigated under ultrahigh vacuum (UHV) condition. Annealing the cantilevers at 1000 degreesC for 30 s in UHV results in an over 1 order of magnitude increase of the quality factor (Q factor), up to about 2.5x10(5) for cantilevers of 30-90 mum in length. The improvement of Q factor was found to be associated with the deoxidization of the surface, as determined by x-ray photoelectron spectroscopy. These results suggest that the surface effects in the ultrathin cantilevers dominate their mechanical behavior. With the promising mechanical behavior, the cantilever can be easily actuated by a laser beam (beam size: about 300x100 mum(2)) with power down to less than 40 muW at a wavelength of 680 nm, corresponding to 480 nW, i.e., 1.64x10(12) photons/s, irradiated on the cantilever surface (60x6 mum(2)). This provides a rather simple way to operate the ultrathin cantilevers dynamically in UHV. Atomic scale force resolution (4.8x10(-17) N) at 300 K is also expected with these cantilevers. (C) 2000 American Institute of Physics. [S0003-6951(00)03749-9].