収差補正ＴＥＭを用いたナノチューブリアクタにおけるナノ物質生成反応の直接観察

二维金属材料的研究进展很大程度上依赖于生长技术的发展。到目前为止，对2D金属制备的研究还很有限，这与2D半导体的情况形成了鲜明的对比，在2D半导体中，包括MoS2、WS2、MoSe2、WSe2在内的各种层状半导体都是以单层的形式被分离出来的。在这项工作中，我们发展了一种简便的方法，用化学气相沉积(CVD)方法制备了二维过渡金属二卤化物(TMDCs)，其中证明了在原子平面的六方氮化硼(HBN)上直接生长了少层的NbS_2(3R相)。用原子力显微镜、光学显微镜、电子显微镜和光谱分析对所生长的NbS_2进行了结构表征，结果表明，利用hBN作为生长衬底是首次成功地CVD生长大单畴尺寸(几个微米)的2D金属TMDCs的关键因素。电输运测量清楚地表明，NbS2原子层到几层厚度都是金属。本研究为二维层状金属材料的可控生长开辟了一条新的合成路线，对于研究二维金属中的丰富物理以及寻找新型的二维超导体具有重要意义。

Progress on researches of two-dimensional (2D) metals strongly relies on development of the growth technique. Studies on preparation of 2D metals have so far been limited, and this is in stark contrast to the situation of 2D semiconductors, where various layered semiconductors, including MoS2, WS2, MoSe2, WSe2, have been isolated in its monolayer form. In this work, we have developed a facile method to prepare 2D metallic transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD) method, where direct growth of few-layered NbS2 (3R phase) on atomically flat hexagonal boron nitride (hBN) has been demonstrated. Structural characterization of the so-grown NbS2 was performed with atomic force microscopy, optical microscopy, electron microscopy and optical spectroscopy, revealing that the utilization of hBN as growth substrates is a key factor for the first successful CVD growth of 2D metallic TMDCs with large single-domain size (several µm). Electrical transport measurements have clearly shown that NbS2 atomic layers down to few-layer-thickness are metal. The current study opens up a new synthetic route for controllable growth of 2D layered metallic materials, which is of great importance in study of rich physics in 2D metals, as well as in search for novel 2D superconductors.