Carbon Nanocrystal-Based Organic Thin-Film Transistors for Nonvolatile Memory Nanodevices

Abstract

Organic semiconductor nonvolatile memory devices were successfully fabricated from organic thin-film transistors (OTFTs) embedded with nanocrystal carbon (nc-C) dots incorporating pentacene as an active layer. The nc-C dots were arranged in the channel region by a focused ion beam (FIB) technique using a precursor of low energy Ga + ions and a carbon source. The formation and morphology of nc-C dot arrays were investigated using a scanning ion microscopy (SIM) and atomic force microscopy (AFM), respectively. The SIM and AFM images show that the nc-C dot array was successfully grown on the SiO2 layer. The density of the two-dimensional nc-C dots was 5 × 10 9 cm −2 . The current-voltage (I − V ) characteristics at room temperature show that the fabricated OTFTs exhibit a memory effect upon the application of forward and reverse bias. Under the effect of gate bias, on and off states were induced and a threshold voltage shift (∆V th = 0.23 V) was obtained. The charge carrier mobility (µ) of the OTFTs is similar in both on and off states. The memory effect was attributed to the nc-C dots in the pentacene-dielectric interface.

Bias Stress and Memory Effect in Pentacene-based Organic Thin-Film Transistors with a Fullerene Layer

“…Specifically, we demonstrate memory effect of pentacene-based OTFTs with a fullerene layer upon the application of bias. These new devices are analogous to our previously reported organic memory devices, where charge storing carbon nanodots are embedded onto gate insulator incorporating pentacene as an active layer [12]. Previously, the devices had an issue of controlling the size of carbon nanodots.…”

“…Memory effects often refer to charge-trapping effect where, programming by injecting charge and erasing by removing the stored charges. This charge transfer in the organic semiconductor layer is readable by measuring the shift of threshold voltage of the transistor [8,10,12]. Therefore, the unique properties of organic semiconductors allow the digital data to be programmed or erased through either electrically or optically.…”