3 years ago

Surface Engineering of ITO Substrates to Improve the Memory Performance of an Asymmetric Conjugated Molecule with a Side Chain

Surface Engineering of ITO Substrates to Improve the Memory Performance of an Asymmetric Conjugated Molecule with a Side Chain
Xue-Feng Cheng, Jian-Mei Lu, Hua Li, Qing-Feng Xu, Dong-Yun Chen, Na-Jun Li, Jing-Hui He, Xiang Hou, Xin Xiao
Organic multilevel random resistive access memory (RRAM) devices with an electrode/organic layer/electrode sandwich-like structure suffer from poor reproducibility, such as low effective ternary device yields and a wide threshold voltage distribution, and improvements through organic material renovation are rather limited. In contrast, engineering of the electrode surfaces rather than molecule design has been demonstrated to boost the performance of organic electronics effectively. Herein, we introduce surface engineering into organic multilevel RRAMs to enhance their ternary memory performance. A new asymmetric conjugated molecule composed of phenothiazine and malononitrile with a side chain (PTZ-PTZO-CN) was fabricated in an indium tin oxide (ITO)/PTZ-PTZO-CN/Al sandwich-like memory device. Modification of the ITO substrate with a phosphonic acid (PA) prior to device fabrication increased the ternary device yield (the ratio of effective ternary device) and narrowed the threshold voltage distribution. The crystallinity analysis revealed that PTZ-PTZO-CN grown on untreated ITO crystallized into two phases. After the surface engineering of ITO, this crystalline ambiguity was eliminated and a sole crystal phase was obtained that was the same as in the powder state. The unified crystal structure and improved grain mosaicity resulted in a lower threshold voltage and, therefore, a higher ternary device yield. Our result demonstrated that PA modification also improved the memory performance of an asymmetric conjugated molecule with a side chain. A better contact: Organic molecules were fabricated on ITO substrates that had been modified with phosphonic acids. These as-fabricated devices displayed better memory behavior, such as a higher ternary device yield and a lower threshold voltage, compared with those fabricated on an unmodified ITO substrate.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/asia.201700706

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