| Jul 08, 2024 |
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(Nanowerk Information) Gallium nitride (GaN)-based light-emitting diodes (LEDs) have reworked the lighting trade by changing typical lighting applied sciences with superior vitality effectivity, longer working life and higher environmental sustainability.
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In recent times, appreciable consideration has been paid to the development towards miniaturization of LEDs, pushed by show gadgets, augmented actuality, digital actuality, and different rising applied sciences. As a result of lack of cost-effective native substrates, the presence of excessive threading dislocation density in heteroepitaxial movies grown on sapphire substrate is a serious limiting issue for system efficiency.
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As well as, Fresnel reflections on the interface between epitaxy and substrate brought on by abrupt modifications within the refractive indices of the fabric cut back the sunshine vitality utilization.
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Distributed nano-nipple array on the compound eyes of moth-like animals have wonderful anti-reflective means and powerful light-absorption capability, which offers nice inspiration for bettering mild utilization. Nonetheless, speedy and exact processing of microstructures on curved surfaces of optoelectronic gadgets is very difficult.
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“The common projection lithography methods are very sensitive to the shape of the substrate, so the accuracy of microstructure definition may be reduced when the substrate has large warps or irregular shapes. We propose a flexible nanoimprint lithography technique that enables high-throughput and high-quality processing of bionic microstructures on curved surfaces,” says Professor Shengjun Zhou.
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| Fabrication of microstructures by steps of thermo-compression molding, imprinting, UV publicity and two-step etching course of. (Picture: Science China Press)
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The researchers first carried out the design of bionic microstructure array and versatile nanoimprinting molds. The fabrication of the microstructures was realized by thermo-compression molding, imprinting, UV publicity and a specifically designed two-step etching course of to acquire a compound-eye-like silica microstructures (NCSM) template. It’s proven that versatile nanoimprinting has adaptability to substrate warpage, permits exact definition of microstructures, and offers good sturdiness. In comparison with projection lithography, productiveness was elevated by an element of 6.4 and financial price financial savings of 25% had been achieved.
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The researchers investigated the expansion conduct of GaN crystals on NCSM template by epitaxial progress interruption experiments. They discovered that adjusting the morphology of the nucleation layer by the NCSM template helps to regulate the expansion orientation of GaN and acquire epitaxial movies with low dislocation density. As well as, the NCSM template can considerably enhance the sunshine extraction effectivity of the gadgets owing to the modulation of photons by the bionic microstructures.
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Professor Sheng Liu says, “Thanks to these two improvements, the light output capability of mini-LEDs based on NCSM template has been greatly enhanced.” He concludes, “This study is promising for the efficient fabrication of microstructures and performance enhancement of optoelectronic devices. In the future, we will continue to explore flexible nanoimprinting technique and expect it to show broader applications.”
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This work has been printed in Science Bulletin (“Flexible nanoimprint lithography enables high-throughput manufacturing of bioinspired microstructures on warped substrates for efficient III-nitride optoelectronic devices”).
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