Control over Memory Performance of Layer-by-Layer Assembled Metal Phthalocyanine Multilayers via Molecular-Level Manipulation
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- 作者：Bonkee Koo ; Hyunhee Baek ; Jinhan Cho
- 刊名：Chemistry of Materials
- 出版年：2012
- 出版时间：March 27, 2012
- 年：2012
- 卷：24
- 期：6
- 页码：1091-1099
- 全文大小：564K
- 年卷期：v.24,no.6(March 27, 2012)
- ISSN：1520-5002
文摘
We herein report on the nonvolatile memory properties of iron phthalocyanine multilayers prepared using an electrostatic layer-by-layer assembly method. Cationic poly(allylamine hydrochloride) (PAH) and anionic iron(III) phthalocyanine-4, 4,鈥?4鈥? 4鈥测€?tetrasulfonic acid (Fe-TsPc) were alternately deposited onto quartz glass, indium tin oxide (ITO), or platinum-coated silicon substrates via electrostatic interactions. The electrochemical response of the PAH/Fe-TsPc, which was obtained from cyclic voltammograms (CV) in solution, indicated that redox reactions occurred at the phthalocyanine unit and at the metallic center. It was found that these redox reactions of the PAH/Fe-TsPc multilayer films in solution could be extended to resistive switching nonvolatile memory based on a charge trap/release mechanism in air. The PAH/Fe-TsPc multilayers sandwiched between the bottom (platinum) and top (Ag or tungsten) electrodes exhibited the characteristics of a resistive switching memory at a relatively low operating voltage of less than 2 V, with a switching speed of about 100 ns and an ON/OFF current ratio of 103. Additionally, it is confirmed using kelvin probe force microscopy (KPFM) that the reversible resistance changes in the PAH/Fe-TsPc multilayers are mainly caused by the externally applied voltage as a result of the trapping and release of charges at redox sites within the Fe-TsPc. Furthermore, in the case where insulating layers of about 2 nm in thickness are inserted between adjacent Fe-TsPc layers, it is demonstrated that these devices can exhibit further improvements in memory performance (ON/OFF current ratio of 106) and a lower power consumption in comparison with PAH/Fe-TsPc multilayers.