Yusuke Kanaoka

Wafer-scale, layer-controlled organic single crystals for high-speed circuit operation

A wafer-scale, 2D organic single-crystalline semiconductor revolutionizes near-field communication. Two-dimensional (2D) layered semiconductors are a novel class of functional materials that are an ideal platform for electronic applications, where the whole electronic states are directly modified by external stimuli adjacent to their electronic channels. Scale-up of the areal coverage while maintaining homogeneous single crystals has been the relevant challenge. We demonstrate that wafer-size single crystals composed of an organic semiconductor bimolecular layer with an excellent mobility of 10 cm2 V−1 s−1 can be successfully formed via a simple one-shot solution process. The well-controlled process to achieve organic single crystals composed of minimum molecular units realizes unprecedented low contact resistance and results in high-speed transistor operation of 20 MHz, which is twice as high as the common frequency used in near-field wireless communication. The capability of the solution process for scale-up coverage of high-mobility organic semiconductors opens up the way for novel 2D nanomaterials to realize products with large-scale integrated circuits on film-based devices.

Effect of postannealing on properties of ZnO-SnO2 thin film transistors

Herein, the influence of postannealing on the properties of ZnO-SnO2 (ZTO) thin-film transistors (TFTs) was investigated. Postannealing in ambient air induced recovery of the electrical properties of wet-etch-damaged TFTs and a decrease in the subthreshold swing. Also, the field effect mobility increased with increasing postannealing temperature. Further improvement of the electrical properties of ZTO TFTs was not obtained with a further increase in annealing time. After postannealing at 200 °C for 60 min in the air, the ZTO TFTs exhibited a field effect mobility of about 10 cm2/V s.Herein, the influence of postannealing on the properties of ZnO-SnO2 (ZTO) thin-film transistors (TFTs) was investigated. Postannealing in ambient air induced recovery of the electrical properties of wet-etch-damaged TFTs and a decrease in the subthreshold swing. Also, the field effect mobility increased with increasing postannealing temperature. Further improvement of the electrical properties of ZTO TFTs was not obtained with a further increase in annealing time. After postannealing at 200 °C for 60 min in the air, the ZTO TFTs exhibited a field effect mobility of about 10 cm2/V s.