Title: Ab initio modeling of transport and thermodynamic stability for hafnia memristive devices

Abstract

HfO₂-based memristive switching devices are currently under intensive investigation due to their high performance and mature fabrication techniques. However, several critical issues have to be addressed to bring them from lab to market. We have recently looked into two important issues with the use of density functional theory methods. One is the wide distribution of device resistance in off-states. We have modeled the switching process of a Pt-HfO₂-Pt structure for which quantized conductance was observed. Oxygen atoms moving inside a conductive oxygen vacancy filament divide the filament into several quantum wells. Device conductance changes exponentially when one oxygen atom moves away from interface into filament. We propose that the high sensitivity of device conductance to the position of oxygen atoms results in the large variation of device off-state resistance. Another issue that we have recently addressed is the poor switching performance of devices based on a TiN-HfO₂-TiN structure. While recent experiments have shown that by inserting an "oxygen scavenger" metal between positive electrode and oxide significantly improves device performance, the fundamental understanding of the improvement is lacking.We provide detailed understanding how scavenger layers improve device performance. First, we show that Ta insertion facilitates formation of on-states by reducing the formationmore » energy. Second, the inserted Ta layer reduces the Schottky barrier height in the off-states by changing interface electric dipole at the oxide electrode interface. Nevertheless, the device maintains a high on/off resistance ratio. Finally, with Ta insertion the on-state conductance becomes much less sensitive to the specific location from which the oxygen was removed from the oxide. In conclusion, our studies provide fundamental understanding needed for enabling realization of a non-volatile memory technology with reduced energy consumption.« less

Authors:

Zhong, Xiaoliang ^[1]; Rungger, Ivan ^[2]; Zapol, Peter ^[1]; Heinonen, Olle  ^[1]

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+ Show Author Affiliations

1. Argonne National Lab. (ANL), Lemont, IL (United States)
2. National Physical Lab., Teddington (United Kingdom)

Publication Date:

2017-09-05

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1402425

Grant/Contract Number:  

AC02-06CH11357

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Computational Electronics

Additional Journal Information:

Journal Volume: 2017; Journal ID: ISSN 1569-8025

Publisher:

Springer

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Density functional theory; Electron transmission; Electronic structure; Hafnium oxide; Memristive switching devices; Oxygen scavenger; Oxygen vacancy; Quantum well; Resonant tunneling; Schottky barrier height; quantum transport