Ferromagnetic nano-conductive filament formed in Ni/TiO2/Pt resistive-switching memory

• Published in: Applied physics. A, Materials science & processing Vol. 118; no. 2; pp. 613 - 619
• Main Authors: Otsuka, Shintaro, Hamada, Yoshifumi, Shimizu, Tomohiro, Shingubara, Shoso
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2015
• Subjects: Characterization and Evaluation of Materials; Condensed Matter Physics; Machines; Manufacturing; Nanotechnology; Optical and Electronic Materials; Physics; Physics and Astronomy; Processes; Surfaces and Interfaces; Thin Films; Conductive Filament; High Resistance State; Residual Resistivity Ratio; TiO2 Layer; Joule Heating
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-014-8769-5

There is a question whether the conductive filament (CF) formed in the oxide layer of a resistive-switching random access memory is made of oxygen vacancies or metallic atoms. We investigated the CF of Ni/TiO 2 /Pt device using temperature coefficient of resistance (TCR), anisotropic magnetoresistance (AMR), and cross-sectional transmission electron microscopy with energy dispersive X-ray analysis (TEM-EDX). The low resistance state (LRS) of the device showed metallic property by TCR measurement. Furthermore, the device in the LRS showed AMR, which was a direct evidence of the formation of ferromagnetic CF. The cross-sectional TEM-EDX observation revealed that a nano-sized Ni precipitation existed in the area nearby a conductive spot. It is intensively suggested that Ni atoms migrated from the adjacent Ni electrode to TiO 2 layer to form the nano-sized ferromagnetic CF.