Role of atomistic structure in the stochastic nature of conductivity in substoichiometric tantalum pentoxide

Journal Article · Tue Mar 22 00:00:00 EDT 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4943163· OSTI ID:1248534

Bondi, Robert James ^[1]; Fox, Brian Philip ^[1]; Marinella, Matthew J. ^[1]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

In this study, first-principles calculations of electrical conductivity (σ_o) are revisited to determine the atomistic origin of its stochasticity in a distribution generated from sampling 14 ab-initio molecular dynamics configurations from 10 independently quenched models (n = 140) of substoichiometric amorphous Ta₂O₅, where each structure contains a neutral O monovacancy (V_O⁰). Structural analysis revealed a distinct minimum Ta-Ta separation (dimer/trimer) corresponding to each V_O⁰ location. Bader charge decomposition using a commonality analysis approach based on the σ_o distribution extremes revealed nanostructural signatures indicating that both the magnitude and distribution of cationic charge on the Ta subnetwork have a profound influence on σ_o. Furthermore, visualization of local defect structures and their electron densities reinforces these conclusions and suggests σ_o in the amorphous oxide is best suppressed by a highly charged, compact Ta cation shell that effectively screens and minimizes localized V_O⁰ interaction with the a-Ta₂O₅ network; conversely, delocalization of V_O⁰ corresponds to metallic character and high σ_o. The random network of a-Ta₂O₅ provides countless variations of an ionic configuration scaffold in which small perturbations affect the electronic charge distribution and result in a fixed-stoichiometry distribution of σ_o; consequently, precisely controlled and highly repeatable oxide fabrication processes are likely paramount for advancement of resistive memory technologies.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1248534
• Alternate ID(s): OSTI ID: 1421088
• Report Number(s): SAND-2016-0408J; JAPIAU; 618608
• Journal Information: Journal of Applied Physics, Vol. 119, Issue 12; ISSN 0021-8979
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
tantalum
crystal structure
amorphous metals
electrical resistivity
carrier density