Phase transition induced micromechanical actuation in VO2 coated cantilever

Abstract

Structural phase transition assisted micromechanical actuation of a vanadium dioxide (VO2) coated silicon microcantilever is presented. A 300 nm polycrystalline VO2 film was deposited over the silicon surface at 520 °C using metal organic chemical vapor deposition. The formation of the M1 monoclinic phase of the as-deposited VO2 film was confirmed by X-ray diffraction studies and further verified by temperature variable Raman spectroscopy. The heated VO2 film exhibits semiconductor-to-metal transition at 74 °C, which produces a change in the electrical resistance almost of three orders in magnitude. Consequently, the VO2 film undergoes structural phase transition from the monoclinic phase (011)M1 to a tetragonal phase (110)R. This generates a compressive stress within the VO2 film resulting in large, reversible cantilever deflection. This deflection was measured with a non-contact 3D optical profilometer, which does not require any vacuum conditions. Upon heating, the VO2 coated silicon cantilever produced a large reversible tip deflection of 14 μm at 50 °C. Several heating and cooling cycles indicate steep changes in the cantilever tip deflection with negligible hysteresis. In addition, the effect of thermal stress induced cantilever deflection was estimated to be as small as 6.4%, and hence can be ignored. These results were found to be repeatable within controlled experimental conditions.

Low-cost VO2(M1) thin films synthesized by ultrasonic nebulized spray pyrolysis of an aqueous combustion mixture for IR photodetection

“…V 2 O 5 was indexed to orthorhombic crystal system of space group Pmmn using JCPDS #77- 2418 (ref. 33) while VO 2 was indexed monoclinic (M1) phase of VO 2 with space group P2 1 /c (JCPDS # 82-0661) 34,35.…”

Strained VO2 Nanostructure Thin Films with an Unaffected Insulator–Metal Transition

“…Crossing the transition temperature (e.g., 340 K), the conversion between monoclinic and rutile phases occurs in VO 2 . Particularly, the insulator (011) plane turns into metal (110) plane with a decreased interlayer spacing . Herein, we present strained VO 2 nanostructure thin films and corresponding IMT behaviors.…”

“…[18] Particularly, the insulator (011) plane turns into metal (110) plane with a decreased interlayer spacing. [19] Herein, we present strained VO 2 nanostructure thin films and corresponding IMT behaviors. Nanostructures have provided an alternative avenue for understanding the SPT and IMT behaviors in the correlated VO 2 .…”

Micro-actuation design in VO2-based bimorph cantilevers

“…Dong et al [18] suggested the 'seesaw' fabrication method for VO 2 -based tri-layer cantilevers, to compensate the residual stress for curvature control. Rajeswaran et al [19] have measured the deflection of a cantilever with VO 2 film using a non-contact 3D optical profilometer and found that after several heating and cooling cycles, the VO 2 -coated silicon cantilever indicate steep changes in the cantilever tip deflection with negligible hysteresis. Rua et al [20] observed that VO 2 films grow on Si substrates with the (011) planes of the monoclinic phase (M 1 ) parallel to the substrate, and transform reversibly to the tetragonal rutile phase (R), with the (110) planes parallel to the substrate.…”