Interface Engineering of Monolayer MoS2/GaN Hybrid Heterostructure: Modified Band Alignment for Photocatalytic Water Splitting Application by Nitridation Treatment
Interface Engineering of Monolayer MoS2/GaN Hybrid Heterostructure: Modified Band Alignment for Photocatalytic Water Splitting Application by Nitridation Treatment
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DOI：
10.1021/acsami.8b01286
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发表时间：
2018-05-23
影响因子：
9.5
通讯作者：
Chen, Kevin J.
中科院分区：
文献类型：
--
作者：
Zhang, Zhaofu;Qian, Qingkai;Chen, Kevin J.
界面工程是处理二维（2D）/三维（3D）混合异质结构的关键策略，因为这种原子层厚的2D材料的性能很容易受到基底环境的影响。本工作通过第一性原理计算和实验分析，系统地研究了纤锌矿GaN表面上无氮化界面层和有氮化界面层的单层MoS2的2D/3D异质结构的结构、电子和光学性质。在顶部堆叠单层 MoS2 之前，可以通过对 GaN 样品表面进行远程 N-2 等离子体处理，将氮化界面层引入 2D/3D 异质结构中。计算结果表明，2D/3D集成异质结构在能量上是有利的，且形成能为负。两个界面都表现出间接带隙，这有利于延长光激发载流子的寿命。同时，氮化处理后MoS2侧的导带边和价带边增大。然后通过对采用改进的湿转移技术构建的MoS2/GaN异质结构进行X射线光电子能谱测量来验证能带对准的修改，这表明未经氮化的MoS2/GaN异质结构显示出II型对准，导带偏移（CBO）仅为0.07 eV。然而，通过界面氮化的部署，由于氮化衬底的特性，MoS2 的能带边缘向上移动了大约 0.5 eV。 CBO的显着增加可以导致GaN侧更好的电子积累能力。经过有效界面处理的氮化2D/3D异质结构表现出干净的带隙和显着的光学吸收能力，有可能用作利用太阳能分解水产生氢气的实用光催化剂。
Interface engineering is a key strategy to deal with the two-dimensional (2D)/three-dimensional (3D) hybrid heterostructure, since the properties of this atomic layer-thick 2D material can easily be impacted by the substrate environment. In this work, the structural, electronic, and optical properties of the 2D/3D heterostructure of monolayer MoS2 on wurtzite GaN surface without and with nitridation interfacial layer are systematically investigated by first principles calculation and experimental analysis. The nitridation interfacial layer can be introduced into the 2D/3D heterostructure by remote N-2 plasma treatment to GaN sample surface prior to stacking monolayer MoS2 on top. The calculation results reveal that the 2D/3D integrated heterostructure is energetically favorable with a negative formation energy. Both interfaces demonstrate indirect band gap, which is a benefit for longer lifetime of the photoexcited carriers. Meanwhile, the conduction band edge and valence band edge of the MoS2 side increases after nitridation treatment. The modification to band alignment is then verified by X-ray photoelectron spectroscopy measurement on MoS2/GaN heterostructures constructed by a modified wet-transfer technique, which indicates that the MoS2/GaN heterostructure without nitridation shows a type-II alignment with a conduction band offset (CBO) of only 0.07 eV. However, by the deployment of interface nitridation, the band edges of MoS2 move upward for similar to 0.5 eV as a result of the nitridized substrate property. The significantly increased CBO could lead to better electron accumulation capability at the GaN side. The nitridized 2D/3D heterostructure with effective interface treatment exhibits a clean band gap and substantial optical absorption ability and could be potentially used as practical photocatalyst for hydrogen generation by water splitting using solar energy.