2D layered materials have emerged in recent years as a new platform to host novel electronic, optical, or excitonic physics and develop unprecedented nanoelectronic and energy applications. By definition, these materials are strongly anisotropic between the basal plane and cross the plane. The structural and property anisotropies inside their basal plane, however, are much less investigated. Black phosphorus, for example, is a 2D material that has such in‐plane anisotropy. Here, a rare chemical form of arsenic, called black‐arsenic (b‐As), is reported as a cousin of black phosphorus, as an extremely anisotropic layered semiconductor. Systematic characterization of the structural, electronic, thermal, and electrical properties of b‐As single crystals is performed, with particular focus on its anisotropies along two in‐plane principle axes, armchair (AC) and zigzag (ZZ). The analysis shows that b‐As exhibits higher or comparable electronic, thermal, and electric transport anisotropies between the AC and ZZ directions than any other known 2D crystals. Such extreme in‐plane anisotropies can potentially implement novel ideas for scientific research and device applications.

中文翻译：

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黑砷：具有极高平面内各向异性的分层半导体

近年来，二维层状材料已经出现，成为承载新颖的电子，光学或激子物理学并发展空前的纳米电子和能源应用的新平台。根据定义，这些材料在基平面和横切平面之间是强烈各向异性的。然而，对其基础平面内的结构和性质各向异性的研究较少。例如，黑磷是具有这种面内各向异性的二维材料。在这里，一种罕见的化学形式的砷称为黑砷（b-As），据称是黑磷的近亲，是一种极各向异性的层状半导体。对b-As单晶的结构，电子，热和电性能进行了系统表征，特别关注了其沿两个面内主轴的各向异性，扶手椅（AC）和锯齿形（ZZ）。分析表明，与任何其他已知的2D晶体相比，b-As在AC和ZZ方向之间展现出更高或相当的电子，热和电各向异性。这种极端的平面各向异性可以为科研和设备应用带来新的思路。