title: Quantized conductance coincides with state instability and excess noise in tantalum oxide memristors.
abstract: Tantalum oxide memristors can switch continuously from a low-conductance semiconducting to a high-conductance metallic state. At the boundary between these two regimes are quantized conductance states, which indicate the formation of a point contact within the oxide characterized by multistable conductance fluctuations and enlarged electronic noise. Here, we observe diverse conductance-dependent noise spectra, including a transition from 1/f(2) (activated transport) to 1/f (flicker noise) as a function of the frequency f, and a large peak in the noise amplitude at the conductance quantum GQ=2e(2)/h, in contrast to suppressed noise at the conductance quantum observed in other systems. We model the stochastic behaviour near the point contact regime using Molecular Dynamics-Langevin simulations and understand the observed frequency-dependent noise behaviour in terms of thermally activated atomic-scale fluctuations that make and break a quantum conductance channel. These results provide insights into switching mechanisms and guidance to device operating ranges for different applications.
authors.affiliation: Hewlett-Packard Laboratories, Palo Alto, California 94304, USA.|HRL Laboratories, LLC, Malibu, California 90265, USA.
authors.forename: Wei
authors.identifier: http://orcid.org/0000-0002-4841-3600
authors.initials: W
authors.lastname: Yi
authors.affiliation: Department of Physics, Loughborough University, Loughborough LE11 3TU, UK.
authors.forename: Sergey E
authors.identifier: http://orcid.org/0000-0003-2771-230X
authors.initials: SE
authors.lastname: Savel'ev
authors.affiliation: Hewlett-Packard Laboratories, Palo Alto, California 94304, USA.|Departamento de Física, UFMG, PO Box 702, Belo Horizonte, 30123-970, Brazil.
authors.forename: Gilberto
authors.initials: G
authors.lastname: Medeiros-Ribeiro
authors.affiliation: Hewlett-Packard Laboratories, Palo Alto, California 94304, USA.|National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
authors.forename: Feng
authors.identifier: http://orcid.org/0000-0002-0962-5424
authors.initials: F
authors.lastname: Miao
authors.affiliation: Hewlett-Packard Laboratories, Palo Alto, California 94304, USA.
authors.forename: M-X
authors.initials: MX
authors.lastname: Zhang
authors.affiliation: Hewlett-Packard Laboratories, Palo Alto, California 94304, USA.|Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: J Joshua
authors.identifier: http://orcid.org/0000-0003-0671-6010
authors.initials: JJ
authors.lastname: Yang
authors.affiliation: Hewlett-Packard Laboratories, Palo Alto, California 94304, USA.|Department of Physics, University of California, Davis, California 95616, USA.|P. L. Kapitza Institute for Physical Problems, 2 Kosygina Str., 119334 Moscow, Russia.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Bratkovsky
authors.affiliation: Hewlett-Packard Laboratories, Palo Alto, California 94304, USA.
authors.forename: R Stanley
authors.initials: RS
authors.lastname: Williams