Complex oxides: Vanadium Oxide
VO2 and V2O3 are two examples of transition metal oxides that show a metal insulator transition whereby the resistance of the material changes 6-7 orders of magnitude along with a structural deformation in a narrow temperature range. Despite the extensive research put into these materials the mechanism behind this phenomenon is still under debate. In parallel, metal–insulator transitions can be exploited in various applications such as resistive switching, neuromorphic computation, sensors and more.
Our research is aimed at understanding the driving force behind the metal-insulator transition and developing applications for these unique materials. We grow our own samples to achieve films of the highest quality available and control material properties through growth conditions. We fabricate devices with state of the art nano-fabrication facilities at the California Institute for Telecommunications and Information Technology. We then use transport measurements, temperature dependent X-ray diffraction (in-house and in synchrotrons), sub-nanosecond electrical measurements, magnetometry, pressure, ion irradiation and more to probe material properties.
We have extensive collaborations with groups from all over the world using an array of well-established as well as newly developed techniques such as scanning probe micrscopy, nano-IR, nano-XRD, scanning laser microscopy, electron holography, muon spin rotation, neutron scattering and more.
Most recently, we have discovered that oxygen migration can be achieved in nano-scale devices of both VO2 and V2O3 by applying large voltage at low temperatures, far from the metal insulator transition. This resistive switching has unique properties compared to those observed in other transition metal oxides since the various vanadium oxides formed in the switching process have different metal insulator transition temperatures.
Del Valle et al. PHYS. REV. APPLIED 8, 054041 (2017).
Figure caption: Resistive switching of VO2: 1st and 2nd R(T) curves show the metal insulator transition. After applying an electrical pulse at low temperature the third R(T) is obtained, showing another hysteresis loop attributed to formation of V2O3 due to oxygen migration in the switching process.
Partial list of other recent publications:
Ultrafast electron-lattice coupling dynamics in VO2 and V2O3 thin films (2017)
Deviation from bulk in the pressure-temperature phase diagram of V2O3 thin films (2017)
Nanotextured phase coexistence in the correlated insulator V2O3 (2017)
Two state coercivity driven by phase coexistence in vanadium sesquioxide/nickel bulk hybrid material (2016)
Avalanches in vanadium sesquioxide nanodevices (2015)