Phase transition and critical issues in structure-property correlations of vanadium oxide

Abstract

Vanadium oxide (VO2) exhibits a very interesting semiconductor to metal transition as the crystal structure changes from tetragonal or rutile to monoclinic upon cooling close to 68°C. The characteristics of this transition are very interesting scientifically and are of immense technological importance due to a variety of sensor- and memory-type applications. We have processed high-quality films of VO2 by pulsed laser deposition, which were grown epitaxially on (0001) sapphire substrate via domain matching epitaxy, involving matching of integral multiples of lattice planes between the film of monoclinic structure and the sapphire substrate. These films exhibit a sharp transition near 68°C, large amplitude, and very small hysteresis, similar to bulk single crystal of VO2. The sharpness and amplitude of the transition and the hysteresis upon heating and cooling are found to be a strong function of crystal structure and microstructure (grain size, characteristics of grain boundaries, and defect content). Here, we propose a model to establish microstructure-property correlations in crystalline and amorphous phases of VO2, which can be used to rationalize our experimental observations as well as those available in the literature. Based upon this model, we predict specific microstructures leading to properties needed for various sensor- and memory-type devices.

Thin Films for Advanced Glazing Applications

“…Even though they offer good transmittance modulation in the visible region, they generally do not offer proper switching in the near IR range of the spectrum or have transitions at suitable temperatures [149]. Among them, vanadium dioxide (VO 2 ) based thin films have been emerged as suitable candidates for TC intelligent glazing applications since they exhibit a sharp transition temperature (T c ) close to room temperature (68 • C) [150].…”

“…The majority of previous investigations have looked at the doping the films with high valence transition metal ions. This causes a reduction in Tc to lower values as the metal dopant causes a partial disruption to the crystal structure, effectively lowering the energy required for the phase transition [150]. Tungsten has been found to be the most efficient dopant, lowering Tc by 7 °C per at % [160], 19 °C per at %, 20 °C per 2 at % [161], and by 23 °C per at % W [162].…”

Atomic and electronic structures of the SrVO3-LaAlO3 interface

“…[1][2][3][4][5][6] Recently, epitaxial growth techniques have been applied to AVO 3 systems, and interesting phenomena and properties in films and on interfaces that are different from that of the bulk were observed. [7][8][9][10][11][12][13][14][15] For example, high conductivity could be constructed at an insulator-insulator interface depending on the interface atomic configuration. 12,14 Because the properties and morphology of the thin films are strongly dependent on the type, orientation, and terminal plane of the substrate, detailed knowledge of the thin film/substrate interface at an atomic scale is indispensable to gain control over and design thin film AVO 3 systems.…”

Metal-insulator transition in nanocomposite VOx films formed by anodic electrodeposition

“…High growth temperature (T > 500 C) is generally required in order to form crystalline materials and achieve a large change in resistivity. 13,14 Electrodeposition in contrast is capable to form highly crystalline transition metal oxide materials such as ZnO 15 and Cu 2 O 16 at temperatures < 100 C. The ability to electrodeposit VO 2 at such low temperatures would lead to significant advantages in the manufacture of electronic devices: by enabling additive filling of lithographic patterns, post-deposition etching processes could be avoided, leading to a low defect density and limiting preferential nucleation sites for phase transformations, which may degrade the quality of the MIT. 14 Other potential advantages include the possibility to form films on non-planar and polymeric substrates, of interest in flexible electronics.…”

“…13,14 Electrodeposition in contrast is capable to form highly crystalline transition metal oxide materials such as ZnO 15 and Cu 2 O 16 at temperatures < 100 C. The ability to electrodeposit VO 2 at such low temperatures would lead to significant advantages in the manufacture of electronic devices: by enabling additive filling of lithographic patterns, post-deposition etching processes could be avoided, leading to a low defect density and limiting preferential nucleation sites for phase transformations, which may degrade the quality of the MIT. 14 Other potential advantages include the possibility to form films on non-planar and polymeric substrates, of interest in flexible electronics. Two approaches have been reported on the electrochemical synthesis of VO 2 ; the first involves 45 days storage of a VO x xerogel prior to annealing at 550 C, 17 while the second consists in the reduction of V 5þ in triethanolamine solutions followed by annealing at 400 C in an Ar atmosphere.…”