| AVS 57th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Monday Sessions |
| Session NS-MoM |
| Session: | Oxide Based Nanoelectronics |
| Presenter: | P. Maksymovych, Oak Ridge National Laboratory |
| Authors: | P. Maksymovych, Oak Ridge National Laboratory J. Seidel, University of California, Berkeley S. Jesse, Oak Ridge National Laboratory P. Yu, University of California, Berkeley Y.-H. Chu, University of California, Berkeley A.P. Baddorf, Oak Ridge National Laboratory R. Ramesh, University of California, Berkeley S.V. Kalinin, Oak Ridge National Laboratory |
| Correspondent: | Click to Email |
The intrinsic coupling of soft-phonon order parameters and electron transport in ferroic materials can usher a wide range of novel physical phenomena with potential for new applications in information technology, energy harvesting and quantum computing. In this talk we will present local conductivity and piezoresposne measurements on the surfaces of uniaxial (Pb(Zr0.2Ti0.8)O3) and multiaxial (BiFeO3) perovskite ferroelectrics, with film thicknesses ranging from 30 nm to 100 nm. Conductive atomic force microscopy revealed that most of these films possesses highly non-linear, and often hysteretic current-voltage characteristics, and in many cases the hystereses could be correlated to local polarization switching induced by the electric field of the AFM tip. In lead zirconate titanate, the large spontaneous polarization produced up to 500-fold enhancement of local conductivity, and the film remained sufficiently conducting in the bias-region significantly smaller than the switching voltage. As a result, this effect can be used for a non-destructive and resistive read-out of the polarization state on length-scales down to 10 nm, implementing a prototypical memory function. Extending the I-V measurements to low-temperatures revealed a strong exponential dependence of the conductivity. We developed a novel analysis scheme, which enabled identifying trap-assisted Fowler-Nordheim tunneling and Poole-Frenkel hopping as two dominant mechanisms behind non-linear I-V curves. Curiously, we have been able to separate the contributions due to interface- and bulk-limited conduction, as well as to visualize spatially-resolved variations due to each transport regime.
We will further discuss the peculiarities of local electron transport through BiFeO3, and in particular the mechanism behind local conductivity of 109o ferroelastic domain walls. Based on a statistical analysis of I-V curves and simultaneous measurements of local transport and piezoresponse, we suggest that the domain wall is not a static conducting object under a biased tip, but instead that a transient, local and microscopically reversible topological distortion of polarization structure at the wall contributes to enhanced electron transport. In particular, it produces a seminal example of ferroic memristive functionality.
The measurements were conducted at the Center for Nanophase Materials Sciences sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. DOE.
[1] P. Maksymovych, S. Jesse, P. Yu, R. Ramesh, A. P. Baddorf, S. V. Kalinin,
Science 324 (2009) 1421.
[2] P. Maksymovych, J. Seidel et. al, submitted (2010)