Large-scale hexagonal boron nitride (h-BN) single crystals are highly desirable not only as the substrate or dielectric for van der Waals heterostructures, but also the promising candidates in optoelectronics, electronics, detectors, as well as recently boomed room-temperature single-photon sources. Here, we report the synthesis of centimeter-scale single-crystal h-BN films with hundreds of micrometer thickness via the metal flux method. The growth control along the out-of-plane and in-plane directions of h-BN crystals is realized by the adjustment of NiCr alloy composition, from which the limited solubility of N atoms can be promoted by high diffusion in molten reactants. This also benefits to forming a distinct interface between the synthesized h-BN crystals and the metal ingot, giving rise to an easy exfoliation of the large area high-quality thick films. Such h-BN crystals have been demonstrated as both self-powered flexible and rigid vacuum-ultraviolet photodetectors, allowing for efficient photodetection in terms of high responsivity, rapid response speed, and high operational temperature. A maximum photoresponsivity of 3.35 mA/W is achieved at a wavelength of 185 nm with an operational temperature spanning to 500 °C (and possibly beyond). The large-area freestanding h-BN single crystal described herein reveals great potential as a high-performance photodetector, and versatile platform for other superb electronic and optoelectronic devices.

中文翻译：

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厘米级单晶六方氮化硼独立式厚薄膜作为高性能 VUV 光电探测器


大规模六方氮化硼 （h-BN） 单晶不仅非常适合作为范德华异质结构的衬底或电介质，而且是光电子学、电子学、探测器以及最近蓬勃发展的室温单光子源的有前途的候选者。在这里，我们报道了通过金属助焊剂法合成具有数百微米厚度的厘米级单晶 h-BN 薄膜。通过调整 NiCr 合金成分来实现沿 h-BN 晶体面外和面内方向的生长控制，其中 N 原子的有限溶解度可以通过在熔融反应物中的高扩散来促进。这也有利于在合成的 h-BN 晶体和金属锭之间形成独特的界面，从而轻松剥离大面积的高质量厚膜。这种 h-BN 晶体已被证明是自供电的柔性和刚性真空紫外光电探测器，可以在高响应性、快速响应速度和高工作温度方面实现高效的光检测。在 185 nm 波长下实现 3.35 mA/W 的最大光响应率，工作温度可达 500 °C（甚至更高）。本文描述的大面积独立式 h-BN 单晶显示出作为高性能光电探测器的巨大潜力，以及用于其他一流电子和光电器件的多功能平台。