Abstract:We have demonstrated pressure-induced transition in a c-axis oriented V2O3 thin film from strongly correlated metal to Mott insulator in a submicrometric region by inducing a local stress using contact atomic force microscopy. To have an access to a pressure range of sub-gigapascal, a tip with a large radius of 335 nm was prepared by chemical vapour deposition of platinum onto a commercial tip with a focused ion beam (FIB). The FIB-modified tip gives a good electrical contact at low working pressures (0.25-0.4… Show more
“…However, the transition temperature is shifted to a lower value compared to the bulk value of around 155 K. This shift in transition temperature has been linked to the stoichiometry of the film 8 as well as the local strain in the films 10 . The ratio between the vertical and lateral lattice parameters has been discussed as a governing factor in modifying the transition temperature 5 both for overall thin film properties as well as under local stress induced using contact probe pressure 29 . Figure 5 Resistance measurements as a function of temperature for films deposited under different substrate temperatures.…”
We present a study of $$\hbox {V}_{2}\hbox {O}_{3}$$
V
2
O
3
thin films grown on c-plane $$\hbox {Al}_{2}\hbox {O}_{3}$$
Al
2
O
3
substrates by reactive dc-magnetron sputtering. Our results reveal three distinct types of films displaying different metal–insulator transitions dependent on the growth conditions. We observe a clear temperature window, spanning 200 $$^{\circ }$$
∘
C, where highly epitaxial films of $$\hbox {V}_{2}\hbox {O}_{3}$$
V
2
O
3
can be obtained wherein the transition can be tuned by controlling the amount of interstitial oxygen in the films through the deposition conditions. Although small structural variations are observed within this window, large differences are observed in the electrical properties of the films with strong differences in the magnitude and temperature of the metal–insulator transition which we attribute to small changes in the stoichiometry and local strain in the films. Altering the sputtering power we are able to tune the characteristics of the metal–insulator transition suppressing and shifting the transition to lower temperatures as the power is reduced. Combined results for all the films fabricated for the study show a preferential increase in the a lattice parameter and reduction in the c lattice parameter with reduced deposition temperature with the film deviating from a constant volume unit cell to a higher volume.
“…However, the transition temperature is shifted to a lower value compared to the bulk value of around 155 K. This shift in transition temperature has been linked to the stoichiometry of the film 8 as well as the local strain in the films 10 . The ratio between the vertical and lateral lattice parameters has been discussed as a governing factor in modifying the transition temperature 5 both for overall thin film properties as well as under local stress induced using contact probe pressure 29 . Figure 5 Resistance measurements as a function of temperature for films deposited under different substrate temperatures.…”
We present a study of $$\hbox {V}_{2}\hbox {O}_{3}$$
V
2
O
3
thin films grown on c-plane $$\hbox {Al}_{2}\hbox {O}_{3}$$
Al
2
O
3
substrates by reactive dc-magnetron sputtering. Our results reveal three distinct types of films displaying different metal–insulator transitions dependent on the growth conditions. We observe a clear temperature window, spanning 200 $$^{\circ }$$
∘
C, where highly epitaxial films of $$\hbox {V}_{2}\hbox {O}_{3}$$
V
2
O
3
can be obtained wherein the transition can be tuned by controlling the amount of interstitial oxygen in the films through the deposition conditions. Although small structural variations are observed within this window, large differences are observed in the electrical properties of the films with strong differences in the magnitude and temperature of the metal–insulator transition which we attribute to small changes in the stoichiometry and local strain in the films. Altering the sputtering power we are able to tune the characteristics of the metal–insulator transition suppressing and shifting the transition to lower temperatures as the power is reduced. Combined results for all the films fabricated for the study show a preferential increase in the a lattice parameter and reduction in the c lattice parameter with reduced deposition temperature with the film deviating from a constant volume unit cell to a higher volume.
“…The application of HP strongly modifies the phase diagram of corundum-type V 2 O 3 . Several studies have investigated the Mott-insulator transition in V 2 O 3 and Cr-doped V 2 O 3 at HP with a range of different experimental techniques [200][201][202][203][204][205]. Here, we would like to first focus on the link between the structural and electronic properties of V 2 O 3 .…”
Pressure is an important thermodynamic parameter, allowing the increase of matter density by reducing interatomic distances that result in a change of interatomic interactions. In this context, the long range in which pressure can be changed (over six orders of magnitude with respect to room pressure) may induce structural changes at a much larger extent than those found by changing temperature or chemical composition. In this article, we review the pressure-induced phase transitions of most sesquioxides, i.e., A2O3 compounds. Sesquioxides constitute a big subfamily of ABO3 compounds, due to their large diversity of chemical compositions. They are very important for Earth and Materials Sciences, thanks to their presence in our planet’s crust and mantle, and their wide variety of technological applications. Recent discoveries, hot spots, controversial questions, and future directions of research are highlighted.
“…In thin film form, several aspects have been shown to affect the transport properties and MIT in V 2 O 3 . The temperature and magnitude of the MIT for films deposited on single crystal substrates, can be influenced with the choice of substrate [4], deposition methods and conditions [5] and tuned through direct application of strain [6,7], hydrostatic pressure [8,9] and doping [10]. Although a few reports on the effect of the thickness of V 2 O 3 on its MIT behavior have been published previously, they have been limited in number and scope and there are significant controversies in the literature on the results.…”
We report on the transport properties of epitaxial vanadium sesquioxide (V2O3) thin films with thicknesses in the range of 1 to 120 nm. Films with the thickness down to nanometer values reveal clear resistivity curves with temperature illustrating that even at these thicknesses, the films are above the percolation threshold and continuous over large distances. The results reveal that with the reducing thickness, the resistivity of the films increases sharply for thicknesses below 4 nm and the metal-insulator transition (MIT) is quenched. We attribute this increase to a strained interface layer of thickness ∼4 nm with in-plane lattice parameters corresponding to the Al2O3 substrate. The interface layer displays a suppressed MIT shifted to higher temperatures and has a room temperature resistivity 6 orders of magnitude higher than the thicker V2O3 films.
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