title: Strain Effects in Epitaxial VO2Thin Films on Columnar Buffer-Layer TiO2/Al2O3Virtual Substrates.
abstract: Epitaxial VO2/TiO2thin film heterostructures were grown on (100) (m-cut) Al2O3substrates via pulsed laser deposition. We have demonstrated the ability to reduce the semiconductor-metal transition (SMT) temperature of VO2to ∼44 °C while retaining a 4 order of magnitude SMT using the TiO2buffer layer. A combination of electrical transport and X-ray diffraction reciprocal space mapping studies help examine the specific strain states of VO2/TiO2/Al2O3heterostructures as a function of TiO2film growth temperatures. Atomic force microscopy and transmission electron microscopy analyses show that the columnar microstructure present in TiO2buffer films is responsible for the partially strained VO2film behavior and subsequently favorable transport characteristics with a lower SMT temperature. Such findings are of crucial importance for both the technological implementation of the VO2system, where reduction of its SMT temperature is widely sought, as well as the broader complex oxide community, where greater understanding of the evolution of microstructure, strain, and functional properties is a high priority.
authors.affiliation: Naval Research Laboratory , 4555 Overlook Avenue, Washington, D.C. 20375, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Breckenfeld
authors.affiliation: Naval Research Laboratory , 4555 Overlook Avenue, Washington, D.C. 20375, United States.
authors.forename: Heungsoo
authors.identifier: http://orcid.org/0000-0002-0181-8010
authors.initials: H
authors.lastname: Kim
authors.affiliation: Naval Research Laboratory , 4555 Overlook Avenue, Washington, D.C. 20375, United States.
authors.forename: Katherine
authors.initials: K
authors.lastname: Burgess
authors.affiliation: Naval Research Laboratory , 4555 Overlook Avenue, Washington, D.C. 20375, United States.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Charipar
authors.affiliation: Nova Research, Inc. , 1900 Elkin Street, Suite 230, Alexandria, Virginia 22308, United States.
authors.forename: Shu-Fan
authors.initials: SF
authors.lastname: Cheng
authors.affiliation: Naval Research Laboratory , 4555 Overlook Avenue, Washington, D.C. 20375, United States.
authors.forename: Rhonda
authors.initials: R
authors.lastname: Stroud
authors.affiliation: Naval Research Laboratory , 4555 Overlook Avenue, Washington, D.C. 20375, United States.
authors.forename: Alberto
authors.initials: A
authors.lastname: Piqué
keywords: TiO2 buffer layers; electrical switching; epitaxial VO2; semiconductor-to-metal transition; strain effect