Growth and stress analyses of vanadium dioxide nanomembranes for controllable rolling

Abstract

Vanadium dioxide (VO2)-based microactuators with fast and highly efficient dynamic responses have become one of the best candidates for microrobots and micromuscles. VO2 microstructures fabricated by rolling nanomembranes with component gradient along the vertical direction are considered to be promising for future applications, and thus need further investigation. Here, we quantify the effects of substrate temperature on the initial internal stress of the nanomembranes and achieve rolled-up single-component VO2 nanomembranes via stress engineering. Through synchrotron radiation x-ray diffraction (XRD) measurements, we find that the stress of nanomembranes is negatively correlated with substrate temperature, and its exact value can be calculated from the shift of the XRD peaks. Moreover, experimental results demonstrate that VO2 nanomembranes deposited on a Si/SiO2 substrate possess lower phase transition temperature and narrower hysteresis loops than those grown on quartz and Al2O3 substrates with similar surface morphology. The upward bending of the VO2 nanomembrane due to the tensile stress gradient from temperature changing during deposition is demonstrated, and the rolled-up VO2 microstructures with tunable stress and narrow hysteresis loops are considered to have advantageous applications in microactuators.