Omambac Karim M, Petrović Marin, Bampoulis Pantelis, Brand Christian, Kriegel Marko A, Dreher Pascal, Janoschka David, Hagemann Ulrich, Hartmann Nils, Valerius Philipp, Michely Thomas, Meyer Zu Heringdorf Frank J, Horn-von Hoegen Michael
Faculty of Physics, University of Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany.
Center of Excellence for Advanced Materials and Sensing Devices, Institute of Physics, Bijenička 46, 10000 Zagreb, Croatia.
ACS Nano. 2021 Apr 27;15(4):7421-7429. doi: 10.1021/acsnano.1c00819. Epub 2021 Mar 24.
Like other 2D materials, the boron-based borophene exhibits interesting structural and electronic properties. While borophene is typically prepared by molecular beam epitaxy, we report here on an alternative way of synthesizing large single-phase borophene domains by segregation-enhanced epitaxy. X-ray photoelectron spectroscopy shows that borazine dosing at 1100 °C onto Ir(111) yields a boron-rich surface without traces of nitrogen. At high temperatures, the borazine thermally decomposes, nitrogen desorbs, and boron diffuses into the substrate. Using time-of-flight secondary ion mass spectrometry, we show that during cooldown the subsurface boron segregates back to the surface where it forms borophene. In this case, electron diffraction reveals a (6 × 2) reconstructed borophene χ-polymorph, and scanning tunneling spectroscopy suggests a Dirac-like behavior. Studying the kinetics of borophene formation in low energy electron microscopy shows that surface steps are bunched during the borophene formation, resulting in elongated and extended borophene domains with exceptional structural order.
与其他二维材料一样，硼基硼烯展现出有趣的结构和电子特性。虽然硼烯通常通过分子束外延法制备，但我们在此报告一种通过偏析增强外延法合成大尺寸单相硼烯畴的替代方法。X射线光电子能谱表明，在1100°C下将硼嗪沉积到Ir(111)上会产生富硼表面，且无氮痕迹。在高温下，硼嗪热分解，氮脱附，硼扩散到衬底中。使用飞行时间二次离子质谱，我们表明在冷却过程中，次表面硼偏析回到表面并形成硼烯。在这种情况下，电子衍射揭示了一种(6×2)重构的硼烯χ-多晶型，扫描隧道谱表明存在类似狄拉克的行为。在低能电子显微镜中研究硼烯形成的动力学表明，在硼烯形成过程中表面台阶会聚集，从而产生具有异常结构有序性的细长且扩展的硼烯畴。
