Evidence of a second-order Peierls-driven metal-insulator transition in crystalline ${\mathrm{NbO}}_{2}$

Evidence of a second-order Peierls-driven metal-insulator transition in crystalline ${NbO}_{2}$

Matthew J. Wahila, Galo Paez, Christopher N. Singh, Anna Regoutz, Shawn Sallis, Mateusz J. Zuba, Jatinkumar Rana, M. Brooks Tellekamp, Jos E. Boschker, Toni Markurt, Jack E. N. Swallow, Leanne A. H. Jones, Tim D. Veal, Wanli Yang, Tien-Lin Lee, Fanny Rodolakis, Jerzy T. Sadowski, David Prendergast, Wei-Cheng Lee, W. Alan Doolittle, and Louis F. J. Piper

Phys. Rev. Materials 3, 074602 – Published 16 July 2019

Abstract

The metal-insulator transition of ${NbO}_{2}$ is thought to be important for the functioning of recent niobium oxide-based memristor devices, and is often described as a Mott transition in these contexts. However, the actual transition mechanism remains unclear, as current devices actually employ electroformed ${NbO}_{x}$ that may be inherently different to crystalline ${NbO}_{2}$ . We report on our synchrotron x-ray spectroscopy and density-functional-theory study of crystalline, epitaxial ${NbO}_{2}$ thin films grown by pulsed laser deposition and molecular beam epitaxy across the metal-insulator transition at $\sim 810^{\circ} C$ . The observed spectral changes reveal a second-order Peierls transition driven by a weakening of Nb dimerization without significant electron correlations, further supported by our density-functional-theory modeling. Our findings indicate that employing crystalline ${NbO}_{2}$ as an active layer in memristor devices may facilitate analog control of the resistivity, whereby Joule-heating can modulate Nb-Nb dimer distance and consequently control the opening of a pseudogap.

Received 28 January 2019
Revised 17 May 2019

DOI:https://doi.org/10.1103/PhysRevMaterials.3.074602

Physics Subject Headings (PhySH)

Composition Crystal structure Density of states Electrical conductivity First-principles calculations Metal-insulator transition Peierls transition Phase transitions Second order phase transitions Structural phase transition Surface reconstruction

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Matthew J. Wahila¹, Galo Paez¹, Christopher N. Singh¹, Anna Regoutz², Shawn Sallis³, Mateusz J. Zuba³, Jatinkumar Rana¹, M. Brooks Tellekamp⁴, Jos E. Boschker⁵, Toni Markurt⁵, Jack E. N. Swallow⁶, Leanne A. H. Jones⁶, Tim D. Veal⁶, Wanli Yang⁷, Tien-Lin Lee⁸, Fanny Rodolakis⁹, Jerzy T. Sadowski¹⁰, David Prendergast¹¹, Wei-Cheng Lee¹, W. Alan Doolittle⁴, and Louis F. J. Piper^1,3,*

¹Department of Physics, Binghamton University, State University of New York, Binghamton, New York 13850, USA
²Department of Materials, Imperial College London, London SW7 2AZ, United Kingdom
³Materials Science and Engineering, Binghamton University, State University of New York, Binghamton, New York 13850, USA
⁴School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
⁵Leibniz-Institut für Kristallzüchtung, Max-Born Straße 2, 12489 Berlin, Germany
⁶Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool L69 7ZF, United Kingdom
⁷Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
⁸Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
⁹Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
¹⁰Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
¹¹The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA