All Two-Dimensional, Flexible, Transparent, and Thinnest\nThin Film Transistor

Abstract

In\nthis article, we report only 10 atomic layer thick, high mobility,\ntransparent thin film transistors (TFTs) with ambipolar device characteristics\nfabricated on both a conventional silicon platform as well as on a\nflexible substrate. Monolayer graphene was used as metal electrodes,\n3–4 atomic layers of h-BN were used as the gate dielectric,\nand finally bilayers of WSe₂ were used as the semiconducting\nchannel material for the TFTs. The field effect carrier mobility was\nextracted to be 45 cm²/(V s), which exceeds the mobility\nvalues of state of the art amorphous silicon based TFTs by ∼100\ntimes. The active device stack of WSe₂–hBN–graphene\nwas found to be more than 88% transparent over the entire visible\nspectrum and the device characteristics were unaltered for in-plane\nmechanical strain of up to 2%. The device demonstrated remarkable\ntemperature stability over 77–400 K. Low contact resistance\nvalue of 1.4 kΩ-μm, subthreshold slope of 90 mv/decade,\ncurrent ON–OFF ratio of 10⁷, and presence of both\nelectron and hole conduction were observed in our all two-dimensional\n(2D) TFTs, which are extremely desirable but rarely reported characteristics\nof most of the organic and inorganic TFTs. To the best of our knowledge,\nthis is the first report of all 2D transparent TFT fabricated on flexible\nsubstrate along with the highest mobility and current ON–OFF\nratio.