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The Interfacial States between Metal/Oxide and the RRAM - Part II
Published online by Cambridge University Press: 01 February 2011
Abstract
Switching resistance of a metal/oxide/metal structure (Pt/PrxCa1-xMnO3/Pt) upon the stimulation of electric pulse has triggered vast research interests and activities for next generation resistive RAM application. Continued from an earlier paper [1] that studied the mechanism of switching resistance, this paper extends to the switching endurance discussion using admittance spectra. Experimental data indicated that there exist interfacial dipoles (or states) at metal/oxide interfaces. Switching resistance comes from the change of interfacial dipoles. However, those interfacial dipoles are all meta-stable indicating the problem of long term switching endurance. We have tested many metal/PCMO contact combinations and characterized those contacts with basic memory criteria: bit separation, data retention, switch endurance, switching speed, and readout limitations. Among them, TiN/PCMO showed large bit separation, excellent data retention, and fast switching speed, but failed long term switching endurance test. Furthermore, the poor switch endurance is discussed using energy-well diagram. Therefore, a material system providing bi-stable states with reasonably large free energy separations is a must for this type of RRAM application. These energy levels can come from either structure or electrochemical potential differences at the metal/oxide interfaces.
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- Copyright © Materials Research Society 2008