Hexagonal boron nitride (h-BN) is a dielectric insulator with a two-dimensional (2D) layered structure. It is an appealing substrate dielectric for many applications due to its favorable properties, such as a wide band gap, chemical inertness and high thermal conductivity. Furthermore, its remarkable mechanical strength makes it possible to use few-layered h-BN as a flexible and transparent substrate, which is ideal for next-generation electronics and optoelectronics. However, the difficulty of preparing high-quality large-area h-BN films has hindered their widespread use. While exceptionally clean and ordered h-BN layers can be prepared from bulk crystals by mechanical cleavage methods, their limited sizes and random thicknesses and orientations are not suitable for practical device applications. On the other hand, the large-area h-BN layers prepared by chemical vapor deposition (CVD) usually exhibit polycrystalline structures, and grain boundaries or dislocations in them can degrade its electronic or mechanical properties. In addition, it is well known that high crystallinity of the substrate is a prerequisite for high quality film growth. Accordingly, large-area single crystalline h-BN layers are desired to fully realize the potential advantages of h-BN in many device applications.<br/>Here, we report the synthesis of epitaxial h-BN films on the centimeter scale while maintaining a low cost of production by re-using the Ni(111) substrates via electrochemical delamination. The heteroepitaxial relationship between h-BN and Ni(111) and the overall crystallinity of the film were thoroughly investigated using a synchrotron radiation x-ray diffraction analysis. The crystallinity at the microscopic scale was further investigated using transmission electron microscopy (TEM)-based techniques. Various physical characterizations confirmed that the grown films exhibited the typical characteristics of h-BN over the entire area. Furthermore, GaN and ZnO thin films were heteroepitaxially grown on epitaxial h-BN films. Homogeneous and continuous films were obtained on epitaxial h-BN sheets with scalability, and exhibited single crystalline structure confirmed by XRD and TEM. For the hybrid materials of semiconductor thin film on h-BN, the semiconductor thin film can work as efficient channels for electrical devices while h-BN layers as a novel insulating substrate offer excellent thermal conductivity, high mechanical strength and elasticity, and/or optical transparency.

Centimeter-sized epitaxial h-BN as a flexible & transferrable template for heteroepitaxial growth of semiconductor thin films

253rd National Meeting (2017)

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