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Smoothening of wrinkles in CVD-grown hexagonal boron nitride films

Abstract

Hexagonal boron nitride (h-BN) is an ideal substrate for two-dimensional (2D) materials because of its unique electrically insulating nature, atomic smoothness and low density of dangling bonds. Although mechanical exfoliation from bulk crystals produce the most pristine flakes, scalable fabrication of devices is still dependent on other more direct synthetic routes. To date, the most utilized method to synthesize large-area h-BN films is by chemical vapor deposition (CVD) using catalytic metal substrates. However, a major drawback for such synthetic films is the manifestation of thermally-induced wrinkles which severely disrupt the smoothness of the h-BN films. Here, we provide detailed characterization to the microstructure of h-BN wrinkles and demonstrate an effective post-synthesis smoothening route by thermal annealing under air. The smoothened h-BN film showed improved surface smoothness by up to 66 % and resulted in a much cleaner surface due to the elimination of polymer residues with no substantial oxidative damage to the film. The unwrinkling effect is attributed to the hydroxylation of the h-BN film as well as the substrate surface, resulting in a reduction in adhesion energy at the interface. Dehydroxylation occurs over time under ambient condition at room temperature and the smoothened film can be restored back with the intrinsic properties of h-BN. This work provides an efficient route to achieved smoother h-BN films which are beneficial for high-performance 2D heterostructure devices.

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Publication details

The article was received on 17 May 2018, accepted on 31 Jul 2018 and first published on 01 Aug 2018


Article type: Paper
DOI: 10.1039/C8NR03984D
Citation: Nanoscale, 2018, Accepted Manuscript
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    Smoothening of wrinkles in CVD-grown hexagonal boron nitride films

    J. Lin, R. Y. Tay, H. Li, L. Jing, S. H. Tsang, H. Wang, M. Zhu, D. McCulloch and E. Teo, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR03984D

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