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Smoothening of wrinkles in CVD-grown hexagonal boron nitride films†
Nanoscale ( IF 5.8 ) Pub Date : 2018-08-01 00:00:00 , DOI: 10.1039/c8nr03984d Jinjun Lin 1, 2, 3, 4 , Roland Yingjie Tay 1, 2, 3, 4, 5 , Hongling Li 1, 2, 3, 4 , Lin Jing 2, 4, 6 , Siu Hon Tsang 4, 5 , Hong Wang 1, 2, 3, 4 , Minmin Zhu 1, 2, 3, 4 , Dougal G. McCulloch 7, 8, 9, 10, 11 , Edwin Hang Tong Teo 1, 2, 3, 4, 6
Nanoscale ( IF 5.8 ) Pub Date : 2018-08-01 00:00:00 , DOI: 10.1039/c8nr03984d Jinjun Lin 1, 2, 3, 4 , Roland Yingjie Tay 1, 2, 3, 4, 5 , Hongling Li 1, 2, 3, 4 , Lin Jing 2, 4, 6 , Siu Hon Tsang 4, 5 , Hong Wang 1, 2, 3, 4 , Minmin Zhu 1, 2, 3, 4 , Dougal G. McCulloch 7, 8, 9, 10, 11 , Edwin Hang Tong Teo 1, 2, 3, 4, 6
Affiliation
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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 produces 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 a detailed characterization study of the microstructure of h-BN wrinkles and demonstrate an effective post-synthesis smoothening route by thermal annealing in air. The smoothened h-BN film showed an 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 conditions 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 achieve smoother h-BN films, which are beneficial for high-performance 2D heterostructure devices.
中文翻译：
CVD生长的六方氮化硼薄膜中皱纹的平滑处理†
六方氮化硼（h-BN）是二维（2D）材料的理想基材，因为它具有独特的电绝缘特性，原子光滑度和悬空键的密度低。尽管从块状晶体进行机械剥落会产生最原始的薄片，但设备的可扩展制造仍取决于其他更直接的合成途径。迄今为止，合成大面积h-BN膜最常用的方法是使用催化金属基材的化学气相沉积（CVD）。然而，这种合成膜的主要缺点是热诱导的皱纹的表现，其严重破坏了h-BN膜的光滑度。在这里，我们提供了对h-BN皱纹的微观结构的详细表征研究，并演示了通过在空气中进行热退火而有效的合成后平滑途径。平滑的h-BN薄膜显示出高达66％的改善的表面光滑度，并且由于消除了聚合物残留物而对薄膜没有实质性的氧化破坏，从而使表面更加清洁。该起皱作用归因于h-BN膜以及基底表面的羟基化，从而导致界面处的粘合能降低。室温下，在环境条件下，脱羟基会随着时间的流逝而发生，光滑的薄膜可以恢复为具有h-BN的固有特性。这项工作为获得更平滑的h-BN膜提供了一条有效途径，这对于高性能2D异质结构器件是有益的。
更新日期：2018-08-01
中文翻译：
CVD生长的六方氮化硼薄膜中皱纹的平滑处理†
六方氮化硼（h-BN）是二维（2D）材料的理想基材，因为它具有独特的电绝缘特性，原子光滑度和悬空键的密度低。尽管从块状晶体进行机械剥落会产生最原始的薄片，但设备的可扩展制造仍取决于其他更直接的合成途径。迄今为止，合成大面积h-BN膜最常用的方法是使用催化金属基材的化学气相沉积（CVD）。然而，这种合成膜的主要缺点是热诱导的皱纹的表现，其严重破坏了h-BN膜的光滑度。在这里，我们提供了对h-BN皱纹的微观结构的详细表征研究，并演示了通过在空气中进行热退火而有效的合成后平滑途径。平滑的h-BN薄膜显示出高达66％的改善的表面光滑度，并且由于消除了聚合物残留物而对薄膜没有实质性的氧化破坏，从而使表面更加清洁。该起皱作用归因于h-BN膜以及基底表面的羟基化，从而导致界面处的粘合能降低。室温下，在环境条件下，脱羟基会随着时间的流逝而发生，光滑的薄膜可以恢复为具有h-BN的固有特性。这项工作为获得更平滑的h-BN膜提供了一条有效途径，这对于高性能2D异质结构器件是有益的。
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