Metal to insulator transition in vanadium sesquioxide films

Fabrication of thin films gives the opportunity to study properties which are not easily accessible in bulk materials. V2O3 is a perfect example: studying the Fermi Surface of this material requires the preparation of an optimal surface and using thin films we show that the electronic structure of V2O3 is accessible by ARPES.

 M. Caputo, et al. App. Surf. Science 574, 151608 (2022).

Since decades V2O3 and Cr-doped V2O3 are studied as prototypical systems for studying a pure Mott-Hubbard transition: undoped V2O3 shows a paramagnetic metal (PM) - antiferromagnetic insulator (AFI) electronic phase transition, accompanied with a corundum - monoclinic structural phase transition at temperatures around 150 K.

Despite an intense theoretical effort to understand the nature of this transition, little guidance form the experiments has been provided. A grat insight in the electronic structure of this system can be obtained using Angle Resolved Photoemission Spectroscopy (ARPES), however, a precise control on the quality of the sample surface must be ensured, a task that proven being partiucarly demanding. Controlling the surface preparation steps is not trivial, and annealing a polished surface can result in surfaces being far different from the truncated V2O3 bulk [9], like vanadyl-terminated, oxygen or vanadium rich terminations, or, in some cases, with vanadium in a completely different oxidation state.Using alternative approaches, however, it is possible to obtain surfaces that can be a good approximation of a bulk truncation. Fabrication of thin films using pulsed laser deposition (PLD) is a good exemple of those.

Using PLD we grew film with a crystal structure perfectly consistent with the bulk, as highlited by X-ray diffraction.


A film consistent with the bulk shows the typical metal-insulator transition as well at the bulk 150 K. 

Having a film close to the bulk is a prerequisite for a meaningful ARPES experiment, but surface quality must be excellent as weel. Long range order, and short range surface quality have also been checked with Low Energy Electron Diffraction (LEED) and Scanning Tunneling Microscopy (STM), showing a perfectly smooth, with well defined steps, surface.



Finally, in-situ transfer gave us the opportunity to observe the electronic structure of V2O3 with ARPES, reavealing its Fermi surface, and the band rearrangment occurring upon the MIT.



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Metal to insulator transition at the surface of V2O3 thin films: An in-situ view

M. Caputo, J. Jandke, E. Cappelli, S. K. Chaluvadi, E. Bonini Guedes, M. Naamneh, G. Vinai, J. Fujii, P. Torelli, I. Vobornik, A. Goldoni, P. Orgiani, F. Baumberger, M.Radovic, G.Panaccione

App. Surf. Science 574, 151608 (2022)

DOI: doi.org/10.1016/j.apsusc.2021.151608

Received: 15 June 2021, Accepted: 211 October 2021

First published online 15 October 2021 
Last Updated on Friday, 03 June 2022 22:56