AVS 52nd International Symposium
    Electronic Materials and Processing Friday Sessions
       Session EM-FrM

Paper EM-FrM3
Physical Mechanisms in Programmable Nanoscale Organic Nonvolatile Memory Devices

Friday, November 4, 2005, 9:00 am, Room 309

Session: Organic Electronic Devices
Presenter: T. Graves-Abe, Princeton University
Authors: T. Graves-Abe, Princeton University
J.C. Sturm, Princeton University
Correspondent: Click to Email
Great interest in novel, low-cost memory technologies has led to the development of a number of promising approaches based on organic thin films.@footnote 1@ We have recently reported memory devices based on 10-nm self-assembled films of 11-mercaptoundecanoic acid (MUA) sandwiched between gold electrodes.@footnote 2@ Devices can be placed into a high-conductance "ON" state by 3- to 4-V pulses and returned to a low-conductance "OFF" state with higher-voltage pulses. Devices have a number of desirable characteristics, including durability (more than 10@super 4@ write/erase cycles without degrading), nonvolatile memory states, fast programming times (<@micro@s), and large current densities (up to 10@super 5@ A/cm@super 2@ at 1 V) to minimize resistance-capacitance delays in large memory arrays for fast access times. Models based on charge-trapping or conducting-path formation have been proposed to describe similar results in other thin films,@footnote 3@ although in practice it is difficult to distinguish between the models. In this work, we report strong evidence that the programmable conductance of our devices is due to the formation and destruction of conductive paths. This evidence includes: i) the presence of multiple step-like increases in current during the transition from OFF to ON states, which are attributed to the formation of a small number (<10) of conducting paths leading to the ON state, ii) the exponential reduction in the time required to form these conductive paths with increased electric field, consistent with the field-assisted diffusion of metal ions into the organic layer to form the paths, iii) the dependence of electrical characteristics on choice of electrode material, and iv) the extremely thin nature of the films. @FootnoteText@ @footnote 1@ Y. Yang et al, MRS Bull. 29, 833 (2004).@footnote 2@ T. Graves-Abe and J. C. Sturm, Mat. Res. Soc. Symp. San Fran., CA, April 2005.@footnote 3@ G. Dearnaley et al, Rep. Prog. Phys. 33, 1129 (1970).