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Impact of oxygen stoichiometry on electroforming and multiple switching modes in TiN/TaOx/Pt based ReRAM

Sharath, S. U. and Joseph, M. J. and Vogel, S. and Hildebrandt, E. and Komissinskiy, P. and Kurian, J. and Schroeder, T. and Alff, L. (2016):
Impact of oxygen stoichiometry on electroforming and multiple switching modes in TiN/TaOx/Pt based ReRAM.
In: Applied Physics Letters, AIP Publishing, p. 173503, 109, (17), ISSN 0003-6951,
[Online-Edition: http://doi.org/10.1063/1.4965872],
[Article]

Abstract

We have investigated the material and electrical properties of tantalum oxide thin films (TaOx) with engineered oxygen contents grown by RF-plasma assisted molecular beam epitaxy. The optical bandgap and the density of the TaOx films change consistently with oxygen contents in the range of 3.63 to 4.66 eV and 12.4 to 9.0 g/cm3, respectively. When exposed to atmosphere, an oxidized Ta2O5-y surface layer forms with a maximal thickness of 1.2 nm depending on the initial oxygen deficiency of the film. X-ray photoelectron spectroscopy studies show that multiple sub-stoichiometric compositions occur in oxygen deficient TaOx thin films, where all valence states of Ta including metallic Ta are possible. Devices of the form Pt/Ta2O5-y/TaOx/TiN exhibit highly tunable forming voltages of 10.5 V to 1.5 V with decreasing oxygen contents in TaOx. While a stable bipolar resistive switching (BRS) occurs in all devices irrespective of oxygen content, unipolar switching was found to coexist with BRS only at higher oxygen contents, which transforms to a threshold switching behaviour in the devices grown under highest oxidation.

Item Type: Article
Erschienen: 2016
Creators: Sharath, S. U. and Joseph, M. J. and Vogel, S. and Hildebrandt, E. and Komissinskiy, P. and Kurian, J. and Schroeder, T. and Alff, L.
Title: Impact of oxygen stoichiometry on electroforming and multiple switching modes in TiN/TaOx/Pt based ReRAM
Language: English
Abstract:

We have investigated the material and electrical properties of tantalum oxide thin films (TaOx) with engineered oxygen contents grown by RF-plasma assisted molecular beam epitaxy. The optical bandgap and the density of the TaOx films change consistently with oxygen contents in the range of 3.63 to 4.66 eV and 12.4 to 9.0 g/cm3, respectively. When exposed to atmosphere, an oxidized Ta2O5-y surface layer forms with a maximal thickness of 1.2 nm depending on the initial oxygen deficiency of the film. X-ray photoelectron spectroscopy studies show that multiple sub-stoichiometric compositions occur in oxygen deficient TaOx thin films, where all valence states of Ta including metallic Ta are possible. Devices of the form Pt/Ta2O5-y/TaOx/TiN exhibit highly tunable forming voltages of 10.5 V to 1.5 V with decreasing oxygen contents in TaOx. While a stable bipolar resistive switching (BRS) occurs in all devices irrespective of oxygen content, unipolar switching was found to coexist with BRS only at higher oxygen contents, which transforms to a threshold switching behaviour in the devices grown under highest oxidation.

Journal or Publication Title: Applied Physics Letters
Volume: 109
Number: 17
Publisher: AIP Publishing
Uncontrolled Keywords: Tantalum, Metallic thin films, Oxidation, Thin film growth, Thin film devices
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Advanced Thin Film Technology
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 18 May 2017 08:37
Official URL: http://doi.org/10.1063/1.4965872
Identification Number: doi:10.1063/1.4965872
Funders: This work was supported by the Deutsche Forschungsgemeinschaft under Project Nos. AL560/13-2 and SCHR1123/7-2., Funding by the Federal Ministry of Education and Research (BMBF, No.16ES0250) and by ENIAC JU (PANACHE) is also gratefully acknowledged.
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