Interdependence of Structure, Morphology, and Phase Transitions in CVD Grown VO2 and V2O3 Nanostructures

Phase selective chemical vapor deposition of nanostructured vanadium dioxide (VO 2 ) and sesquioxide (V 2 O 3 ) was achieved by deploying [V(O R ) 4 ] n ( R = t Bu, n = 1 ( 1 ), R = Et, n = 3 ( 2 ), R = Me, n = 4 ( 3 )). Use of [V(O t Bu) 4 ] ( 1 ) produced thin films of monoclinic VO 2 (M1) at 700 and 800 °C consisting of anisotropic nanostructures with high crystallinity and small hysteresis in the metal-to-semiconductor transition (MST). Film morphologies manifested strong dependence on growth temperatures and exhibited pronounced texturing effects at high temperatures (>700 °C). The microstructure of the films was found to significantly affect the MST behavior of VO 2 films. DTA measurements of VO 2 films showed MST at 63 °C (700 °C) and 65 °C (800 °C), much lower than the transition temperature observed in single crystal material (68 °C). Precursors were characterized in the solid state (XRD) and solution state (temperature dependent EPR, NMR) to reveal an association–dissociation equilibrium in solution (complexes 2 and 3 ), involving monomeric, dimeric, and oligomeric species. Use of 2 and 3 as single precursors produced thin films of crystalline V 2 O 3 consisting of nanosheets (5 nm) with a flower-like morphology.