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Recently, copper oxide (CuO)-based visible-light photodetectors have attracted great interest due to their narrow bandgap (1.2 eV), low cost, and ease of fabrication. However, there has been insufficient theoretical analysis and study of CuO-based photodetectors, resulting in inferior performance in terms of responsivity, detectivity, and response speed. This work develops a method to enhance the performance of CuO photodetectors by engineering a grain structure based on a newly-developed theoretical model. In the developed theoretical grain-structure model, the grain size and the connections between grains are considered because they can strongly affect the optoelectronic characteristics of CuO photodetectors. Based upon the proposed model, the engineered CuO device achieves enhanced optoelectronic performance. The engineered device shows high responsivity of 15.3 A/W and detectivity of 1.08 × 1011 Jones, which are 18 and 50 times better than those of the unoptimized device, and also shows fast rising and decaying response speeds of 0.682 s and 1.77 s, respectively. In addition, the proposed method is suitable for the mass-production of performance-enhanced, reliable photodetectors. By using a conventional semiconductor fabrication process, a photodetector-array is demonstrated on a 4-inch wafer. The fabricated devices show uniform, high, and stable optoelectronic performance for a month.

A major obstacle to the industrial application of nanowires is difficulty in fabricating nanowire devices with uniform performance. In this study, we newly developed a wafer-level uniformly size-controlled nanowire fabrication method for reliable demonstration of a high-yield, uniform nano-sensor device. We show that the developed fabrication method can be used to simply fabricate remarkably small nanowires (sub-50 nm) with a wide material selection. Importantly, the fabricated nanowires have ultra-high size uniformity on the 4-inch wafer. Finally, we demonstrate nanowire-based hydrogen (H 2 ) sensors using the developed method. Owing to the geometric uniformity of the fabricated nanowires, the sensor devices achieved highly uniform sensitivity of 10.9±0.5 % at a 2% H 2 concentration.

This paper reports a high-sensitivity wearable transparent pressure sensor by maximizing the percolation effect using a sub-100 nm nano-valley. The secret to achieving high sensitivity is to make the nano-valley as narrow as possible to maximize the percolation effect (stress concentration effect). The narrow nano-valley pressure sensor showed a remarkable 400% enhancement in sensitivity compared to a sensor with no nano-valley while maintaining a high transmittance of 83%. This sensitivity value is higher than those of the previous wearable transparent pressure sensors. The fabricated sensor also showed high durability with low variation of 1.2% in repeated pressing of up to 100,000 times under 100 kPa pressure.