An influence of bottom electrode material on electrical conduction and resistance switching of TiO_x thin films

¹ Faculty of Materials Science, University of Science, Vietnam National University, Ho Chi Minh, Vietnam
² Laboratory of Advanced Materials, University of Science, Vietnam National University, Ho Chi Minh, Vietnam
³ Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, Japan
⁴ School of Materials Science and Engineering, Inha University, Incheon 402-751, South Korea
⁵ School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746, South Korea
⁶ Faculty of Engineering Physics and Nanotechnology, University of Engineering and Technology, Vietnam National University, Hanoi, Vietnam

^a e-mail: pbthang@skku.edu

Received: 27 May 2013
Revised: 23 September 2013
Accepted: 7 November 2013
Published online: 9 December 2013

Abstract

We investigated the electrical conduction and resistance switching mechanisms of TiO_x thin films grown on three kinds of bottom electrode at room temperature (an inert Pt, an active Ti and fluorine tin oxide FTO electrodes). The bottom electrode materials strongly affect the I-V characteristics and switching parameters. The I-V characteristic is explained through the presence of interface states in the metal electrode devices (Pt and Ti) and the work function in the metal oxide device (FTO). The Pt device has the smallest V_SET and largest switching ratio, while the Ti device shows the largest V_SET and smallest switching ratio. XPS data shows non-lattice oxygen in TiO_x films. Therefore, the proposed bipolar resistance switching arises from formation and rupture of filament paths, generated by the movement of oxygen vacancies. All devices depict the same electrical conductions, trap-controlled space-charge-limited, FN tunneling and Ohmic conductions for a high resistance state and a low resistance state, respectively. In this study, the rarely reported FN tunneling conduction in published TiO_x-based ReRAM device was found, which can be attributed to an influence of the bottom electrode on the electronic distribution in devices.