title: Atomic Origins of Monoclinic-Tetragonal (Rutile) Phase Transition in Doped VO2 Nanowires.
abstract: There has been long-standing interest in tuning the metal-insulator phase transition in vanadium dioxide (VO2) via the addition of chemical dopants. However, the underlying mechanisms by which doping elements regulate the phase transition in VO2 are poorly understood. Taking advantage of aberration-corrected scanning transmission electron microscopy, we reveal the atomistic origins by which tungsten (W) dopants influence the phase transition in single crystalline WxV1-xO2 nanowires. Our atomically resolved strain maps clearly show the localized strain normal to the (122̅) lattice planes of the low W-doped monoclinic structure (insulator). These strain maps demonstrate how anisotropic localized stress created by dopants in the monoclinic structure accelerates the phase transition and lead to relaxation of structure in tetragonal form. In contrast, the strain distribution in the high W-doped VO2 structure is relatively uniform as a result of transition to tetragonal (metallic) phase. The directional strain gradients are furthermore corroborated by density functional theory calculations that show the energetic consequences of distortions to the local structure. These findings pave the roadmap for lattice-stress engineering of the MIT behavior in strongly correlated materials for specific applications such as ultrafast electronic switches and electro-optical sensors.
authors.affiliation: Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University , Houghton, Michigan 49933-1295, United States.|Department of Physics, University of Illinois at Chicago , Chicago, Illinois 60607-7059, United States.
authors.forename: Hasti
authors.initials: H
authors.lastname: Asayesh-Ardakani
authors.affiliation: Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University , Houghton, Michigan 49933-1295, United States.|Department of Physics, University of Illinois at Chicago , Chicago, Illinois 60607-7059, United States.
authors.forename: Anmin
authors.initials: A
authors.lastname: Nie
authors.affiliation: Department of Chemistry, University at Buffalo, State University of New York , Buffalo, New York 14260-3000, United States.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Marley
authors.affiliation: Advanced Membranes and Porous Materials Center, King Abdullah University of Science & Technology , Thuwal 23955-6900, Kingdom of Saudi Arabia.
authors.forename: Yihan
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Physics, University of Illinois at Chicago , Chicago, Illinois 60607-7059, United States.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Phillips
authors.affiliation: Department of Physics, University at Buffalo, State University of New York , Buffalo, New York 14260-3000, United States.
authors.forename: Sujay
authors.initials: S
authors.lastname: Singh
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Illinois at Chicago , Chicago, Illinois 60607-7059, United States.
authors.forename: Farzad
authors.initials: F
authors.lastname: Mashayek
authors.affiliation: Department of Physics, University at Buffalo, State University of New York , Buffalo, New York 14260-3000, United States.
authors.forename: Ganapathy
authors.initials: G
authors.lastname: Sambandamurthy
authors.affiliation: Research Resource Center, University of Illinois at Chicago , Chicago, Illinois 60607-7059, United States.
authors.forename: Ke-Bin
authors.initials: KB
authors.lastname: Low
authors.affiliation: Department of Physics, University of Illinois at Chicago , Chicago, Illinois 60607-7059, United States.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Klie
authors.affiliation: Department of Chemistry, University at Buffalo, State University of New York , Buffalo, New York 14260-3000, United States.
authors.forename: Sarbajit
authors.initials: S
authors.lastname: Banerjee
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Odegard
authors.affiliation: Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University , Houghton, Michigan 49933-1295, United States.|Department of Physics, University of Illinois at Chicago , Chicago, Illinois 60607-7059, United States.|Department of Mechanical and Industrial Engineering, University of Illinois at Chicago , Chicago, Illinois 60607-7059, United States.
authors.forename: Reza
authors.initials: R
authors.lastname: Shahbazian-Yassar
keywords: VO2; doping; nanowires; phase transition; scanning transmission electron microscopy; strain mapping