Synthesis of vanadium oxide films with controlled morphologies: Impact on the metal-insulator transition behaviour
S. Kumar, D. Lenoble, F. Maury, and N. Bahlawane
Physica Status Solidi A, vol. 212, no. 7, pp. 1582-1587, 2015
Precise control over the growth of VO2 films with different morphologies is achieved by varying the deposition parameters in the DLI-MOCVD process such as temperature, pressure, concentration of precursor and time of deposition. In this study, thin films of VO2 with wide range of morphologies having Metal to Insulator Transition (MIT) temperature of (τc) ∼ 52 °C were deposited. Adjusting the process parameters has allowed the growth of highly porous nanocrystalline films and dense microcrystalline films with controlled crystallite size up to several hundred nanometres. Vanadium (V) oxy tri-isopropoxide was used in this study as a single source precursor. Porous films lead to a diffuse change in resistivity across the transition temperature while the crystalline films have sharp and high resistivity drop (Δρ). This enabled a qualitative study of the MIT behaviour with respect to the microstructure of the films and correlates the effect of deposition conditions to the obtained morphologies. Fine control over the morphology without additional doping or post deposition process provides the ability to tailor VO2 thin films for their respective applications. Scanning electron microscopy, Raman spectroscopy and X-ray diffraction were used to characterize the microstructure of the films while electrical resistivity measurements were carried out to observe the MIT behaviour of the films.