Volatility Transition from Short‐Term to Long‐Term Photonic Transistor Memory by Using Smectic Liquid Crystalline Molecules as a Floating Gate

Abstract

AbstractRod‐like molecules with liquid crystalline phase transitions show highly ordered stacking and orientation, which is promising as the floating gate electret in high‐performance photonic field‐effect transistor (FET) memory. In this work, a series of rod‐like molecules, alkyl‐dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (Cn‐DNTT), are investigated with a smectic liquid crystalline phase transition. The photonic FET memory featuring these rod‐like molecules is correlated with their morphology and crystallographic properties. A volatility transition from short−term to long−term memory behavior is found by utilizing the smectic liquid crystalline phase transitions (SmX, X = H, K, E) to orient the stacking in the floating gate. Accordingly, the annealed 2,9‐didecyldinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (C10‐DNTT) polycrystalline film with the optimized alkyl chain length achieved preferential end‐on orientation associated with the herringbone‐type stacking to store charges during photowriting, along with effective charge tunneling for the trapped charges during electrical erasing. Therefore, the resultant photonic FET memory provided a superior ON/OFF current ratio of up to 105 with retention of 104 after 104 s. The results demonstrate that rod‐like molecules with smectic liquid crystalline phase and highly ordered orientation have great potentials for developing high‐performance photonic FET memory.