Of all the transition metal oxides which exhibit metal-insulator transitions (MIT), one of the most extensively studied in recent years is the vanadium sesquioxide (V 2 O 3 ), both from experimental and theoretical point of view. At a transition temperature of about 160 K at an ambient pressure of 1 atm, pure V 2 O 3 transforms from a rhombohedral paramagnetic metallic (PM) to a monoclinic antiferromagnetic insulating (AFI) phase upon cooling, with a jump in the resistivity of about seven orders of magnitude. Experimental studies have focused more on bulk V 2 O 3 and recently there have been significant interest in thin film fabrication of this material due to potential applications as thermal sensors, current limiters, Positive Temperature Coefficient (PTC) thermistors, and optical switches.
This study addresses the deposition, characterization, and properties of high-quality epitaxial V 2 O 3 thin films grown on a -, c -Al 2 O 3 and c-LiTaO 3 substrates by a straightforward method of pulsed laser deposition (PLD). Various characterization techniques including X-ray diffraction, atomic force microscopy, scanning electron microscopy, and X-ray photoemission spectroscopy were used to examine the structural, crystallographic, and surface properties, while four point probe resistivity measurements were used to examine the electrical properties of the films. V 2 O 3 thin films of different thicknesses ranging from 10-450 nm were deposited on c -Al 2 O 3 and c -LiTaO 3 substrates by PLD to understand also the role of epitaxial strains. Resistivity measurements showed that depending on the thicknesses of films, different electrical transitions were exhibited by the samples. While some of the samples displayed the expected metal-insulator transition typical of bulk V 2 O 3 , some showed insulating behavior only and others exhibited metallic characteristics only over the whole temperature range. For example, for films on c -LiTaO 3 with increasing film thickness, first an insulator-insulator, then a metal-insulator, followed by a metal-metal transition is observed. Thicker films (>202 nm) remain metallic in the temperature range of the measurements.
