title: Direct observation of metal-insulator transition in single-crystalline germanium telluride nanowire memory devices prior to amorphization.
abstract: Structural defects and their dynamics play an important role in controlling the behavior of phase-change materials (PCM) used in low-power nonvolatile memory devices. However, not much is known about the influence of disorder on the electronic properties of crystalline PCM prior to a structural phase-change. Here, we show that the application of voltage pulses to single-crystalline GeTe nanowire memory devices introduces structural disorder in the form of dislocations and antiphase boundaries (APB). The dynamic evolution and pile-up of APBs increases disorder at a local region of the nanowire, which electronically transforms it from a metal to a dirty metal to an insulator, while still retaining single-crystalline long-range order. We also observe that close to this metal-insulator transition, precise control over the applied voltage is required to create an insulating state; otherwise the system ends up in a more disordered amorphous phase suggesting the role of electronic instabilities during the structural phase-change.
authors.affiliation: Department of Materials Science and Engineering, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Pavan
authors.initials: P
authors.lastname: Nukala
authors.forename: Rahul
authors.initials: R
authors.lastname: Agarwal
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Qian
authors.forename: Moon Hyung
authors.initials: MH
authors.lastname: Jang
authors.forename: Sajal
authors.initials: S
authors.lastname: Dhara
authors.forename: Karthik
authors.initials: K
authors.lastname: Kumar
authors.forename: A T Charlie
authors.initials: AT
authors.lastname: Johnson
authors.forename: Ju
authors.initials: J
authors.lastname: Li
authors.forename: Ritesh
authors.initials: R
authors.lastname: Agarwal