Rapid Charge Storage and Release at Etching-Assist Electret in Organic Transistors for Memories, Photodetectors, and Artificial Synapses

Insulator materials can trap charges, referring to electrets, which are attractive for transistors and memories. However, insulators intrinsically exhibit high electrical resistance, thus the charge injection and release inside insulators typically need high voltage or long bias time, limiting the applications that require high writing/erasing speed. In this work, insulator polymer polystyrene (PS) film is treated by a soft plasma, which selectively induces a high density of charge traps at the top surface, without changing the electronic properties of the underneath materials. The thus-prepared surface is easily occupied by external neat charges to form a meso-stable electret. Subsequently, the electret is used as an ultra-thin charge trapping layer to build transistors for some applications. Consequently, in transistor architecture, the charge injection and release at soft plasma treated PS surface can be more easily achieved in a short stimulus as compared with pristine PS counterpart, and the density of captured holes under gate bias reaches 2.9 × 10¹² cm⁻² in 1 ms. Under UV irradiation, charge transfer occurs from the photo-excited semiconductor to the electret, contributing to the rapid release of the stored holes. This soft plasma-generated electret is then utilized for flash-type memories, photodetectors, and artificial synapses.