In Situ Monitoring of the Growth, Intermediate Phase Transformations and Templating of Single Crystal VO₂ Nanowires and Nanoplatelets

Abstract

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(2)O(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.

Thermochromic VO2 nanorods made by sputter deposition: Growth conditions and optical modeling

“…11,[65][66][67] Consequently it is of great importance to develop efficient methods to prepare such nanoparticles in large quantities and over extended surfaces. In fact, there have been numerous prior studies on VO 2 -based nanoparticles, and recent investigations have been conducted with hydrothermal/solvothermal/colloidal techniques, 27,49,50,64, vapor transport, 56,[109][110][111][112][113][114][115] anodization, 116 polymer-assisted deposition, 117,118 and templating. 29,119 References to earlier studies on the manufacturing of nanostructured VO 2 -based materials can be found elsewhere.…”

Self-Assembly and Horizontal Orientation Growth of VO2 Nanowires

“…Considerable effort have in recent years been expended to the control of the growth of VO 2 NWs using simple thermal evaporation methods14151617. Usually, VO 2 NWs are preferentially grown on substrates such as silicon, oxidized silicon surface, fused quartz, etc., through a vapor-solid (VS) process17.…”

“…Other methods that have been explored include: 1) directed and heteroepitaxial growth of VO 2 NWs on special substrates with a certain lattice match of surfaces such as a-cut/c-cut sapphire, c-cut GaN, (110) TiO 2 etc. 1518 2) several alternative templating techniques for the control of the position and orientation of VO 2 nanostructures including: (a) surface patterning with precursor powder16 and (b) templating against a microstructure substrate15. However, the efforts that have been expended in this direction suffer from drawbacks such as expensive epitaxial substrates as mentioned above and/or a poor product density.…”

Tailoring of the thermomechanical performance of VO2 nanowire bimorph actuators by ion implantation

“…In reducing atmosphere thermal decomposition at 700°C (2 V 2 O 5 ! 4VO 2 þ O 2 ) results in nucleation of thermally stable VO 2 nanocrystals with a high melting point of 1970°C [22]. As aforementioned, the nanowires grow preferentially in c R crystal axis direction by vapor transport of VO 2 close to the substrate edge in form of free standing single-clamped VO 2 nanowires with sub-lm diameters between of 120 up to 370 nm and lengths in the range of 30-70 lm.…”