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Keywords:

  • electron transport;
  • electronic structure;
  • heterocycles;
  • molecular devices;
  • thin films

Abstract

We report the synthesis of two imidazole-based small molecules with different planarity of terminal aromatic rings and their application in memory devices with a sandwich configuration. The optical, electric, and the on-based device performances were systematically investigated. Surprisingly, the device based on BT-PMZ exhibited volatile static random access memory (SRAM) behavior, whereas that based on BT-BMZ showed nonvolatile write-once-read-many-times (WORM) behavior. Further studies on the film morphology and the molecular electronic structure were carried out to investigate the underlying mechanism for the large difference in their performance. Moreover, the performance of the device that incorporates a LiF buffer layer (5 nm) embedded at the interface between the BT-BMZ active layer and the Al top electrode as well as that of the device with a cold-deposited top electrode of mercury droplet was further investigated. At that point a dramatic change in memory performance of the devices from the WORM to SRAM type was observed. The intrinsic volatile SRAM performance for the two molecules results from the moderate electron-withdrawing strength of the acceptor moieties and thus weak trapping of the charge carriers.