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All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics
Published on: January 19, 2018
Conducting polymer memory devices based on dynamic doping
Sudip Barman1, Fengjun Deng, Richard L McCreery
1National Institute for Nanotechnology, Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2M9.
Journal of the American Chemical Society
|July 24, 2008
Summary
Thin polypyrrole/TiO2 molecular junctions show promise for nonvolatile memory. These dynamic doping devices offer long retention times, exceeding commercial memory by 5 orders of magnitude.
Area of Science:
- Materials Science
- Solid-State Physics
- Molecular Electronics
Background:
- Conventional polymer electronic devices often utilize thicker polymer layers.
- Nonvolatile memory devices require stable retention of data.
- Polypyrrole (PPy) and Titanium Dioxide (TiO2) are known materials in electronic applications.
Purpose of the Study:
- To investigate molecular electronic junctions of polypyrrole (PPy) and TiO2 as potential nonvolatile memory devices.
- To explore the effect of a significantly thinned polymer layer on device performance.
- To understand the mechanism behind the observed electrical switching behavior.
Main Methods:
- Fabrication of molecular electronic junctions with a 20 nm PPy layer and a 10 nm TiO2 layer between carbon and gold electrodes.
- Application of electrical bias pulses to induce oxidation and reduction of the PPy layer.
- Measurement of junction conductance changes and retention characteristics.
- Comparison with devices using fluorene or SiO2.
Main Results:
- The PPy/TiO2 junctions exhibited dynamic oxidation and reduction of the PPy layer upon applied bias.
- A significant increase in conductance was observed under positive bias (conducting polaron state), reversed by negative bias.
- Switching speeds as fast as 10 microseconds were achieved.
- The conducting state persisted for over a week, with over 1700 read/write/erase cycles demonstrated.
- The PPy/TiO2 junctions showed superior retention compared to fluorene/TiO2 devices and absent conductance changes with SiO2 substitution.
Conclusions:
- The observed phenomena are consistent with "dynamic doping" of the solid-state polymer layer, potentially involving mobile ions.
- The thinned PPy/TiO2 junctions demonstrate potential as nonvolatile memory with excellent data retention, despite slower speeds than commercial DRAM.
- The results highlight the importance of the polymer layer and the specific oxide (TiO2) for achieving these memory characteristics.
