In situ monitoring of the growth, intermediate phase transformations and templating of single crystal VO_2 nanowires and nanoplatelets

摘要

Direct in situ optical and photoelectron emission microscopy observations of the nucleation and growth of VO_2 meso- and nanostructures using thermal transport of V_2O_5 precursor in a vacuum or in an inert-gas environment were conducted. During nanostructure reductive growth, the formation, coexistence, and transformation of the intermediate oxide phases and morphologies were observed and characterized structurally and compositionally. The composition, structure, and morphology of the resultant nanostructures appeared to be a product of the interplay between kinetic and thermodynamic factors during multiple phase transformations. By rationally "navigating" the growth parameters using knowledge of the vanadium-oxygen temperature-composition phase diagram, wetting behavior, and epitaxial relationships of the intermediate phases with the substrate, control over growth direction, faceting, shape, and elastic strain of the nanostructures can be achieved. Such versatile control over the properties of single-crystal VO_2 nano- and mesostructures will facilitate their application in MEMS, sensors, and optoelectronics.