Bellus Matthew Z, Yang Zhibin, Zereshki Peymon, Hao Jianhua, Lau Shu Ping, Zhao Hui
Department of Physics and Astronomy, The University of Kansas, Lawrence, Kansas 66045, USA.
Nanoscale Horiz. 2019 Jan 1;4(1):236-242. doi: 10.1039/c8nh00234g. Epub 2018 Oct 10.
The newly developed van der Waals materials allow fabrication of multilayer heterostructures. Early efforts have mostly focused on heterostructures formed by similar materials. More recently, however, attempts have been made to expand the types of materials, such as topological insulators and organic semiconductors. Here we introduce an amorphous semiconductor to the material library for constructing van der Waals heterostructures. Samples composed of 2 nm amorphous black phosphorus synthesized by pulsed laser deposition and monolayer WS obtained by mechanical exfoliation were fabricated by dry transfer. Photoluminescence measurements revealed that photocarriers excited in WS of the heterostructure transfer to amorphous black phosphorus, in the form of either energy or charge transfer, on a time scale shorter than the exciton lifetime in WS. Transient absorption measurements further indicate that holes can efficiently transfer from WS to amorphous black phosphorus. However, interlayer electron transfer in either direction was found to be absent. The lack of electron transfer from amorphous black phosphorus to WS is attributed to the localized electronic states in the amorphous semiconductor. Furthermore, we show that a hexagonal BN bilayer can effectively change the hole transfer process.
新开发的范德华材料可用于制造多层异质结构。早期的工作主要集中在由相似材料形成的异质结构上。然而，最近人们尝试扩大材料类型，如拓扑绝缘体和有机半导体。在这里，我们将一种非晶半导体引入用于构建范德华异质结构的材料库中。通过脉冲激光沉积合成的2纳米非晶黑磷和通过机械剥离获得的单层WS组成的样品通过干法转移制备而成。光致发光测量表明，在异质结构的WS中激发的光载流子以能量转移或电荷转移的形式在比WS中激子寿命更短的时间尺度上转移到非晶黑磷上。瞬态吸收测量进一步表明，空穴可以有效地从WS转移到非晶黑磷上。然而，发现不存在任何方向的层间电子转移。非晶黑磷向WS缺乏电子转移归因于非晶半导体中的局域电子态。此外，我们表明，六方BN双层可以有效地改变空穴转移过程。
