Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Magneto-Photoelectrical Composite and Interface Science, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China.
Nanoscale. 2019 Nov 28;11(46):22432-22439. doi: 10.1039/c9nr07599b.
Strain is usually unavoidable in the fabrication of devices based on two-dimensional (2D) transition metal chalcogenides (TMDCs). When metals are deposited onto monolayer TMDCs, strain can be induced at metal-TMDC interfaces and evolves with elapsed time. However, the effect of the substrate on the strain evolution at the metal-TMDC interfaces is still unclear, which hinders the development of reliable 2D TMDC-based devices with perfect contacts. In this work, we investigated the evolution of metal-induced local strains for Ag-deposited monolayer MoS2 on three kinds of substrates with different interface interactions, i.e., sapphire, SiO2/Si, and mica. The interface interaction between MoS2 and sapphire is the strongest, while that between MoS2 and mica is the weakest. With the splitting of MoS2 Raman peaks as an indicator of local strain, the evolution behavior of the local strain at the Ag-MoS2 interfaces is found to greatly depend on the interface interactions from the underlying substrates. With elapsed time, the local strain is best preserved on sapphire but relaxed most easily on mica. Density-functional theory calculations show that the adsorption energies at the interfaces are different for MoS2 on different substrates, suggesting that the interface interaction between monolayer MoS2 and the substrates is crucial for the strain evolution. Our work is of benefit for the study of stability and reliability of devices based on TMDCs, particularly for flexible electronic devices.
在基于二维（2D）过渡金属硫属化物（TMDC）的器件制造中，应变通常是不可避免的。当金属沉积在单层 TMDC 上时，应变可以在金属-TMDC 界面处产生，并随着时间的推移而演变。然而，衬底对金属-TMDC 界面处应变演变的影响尚不清楚，这阻碍了具有完美接触的可靠 2D TMDC 基器件的发展。在这项工作中，我们研究了三种具有不同界面相互作用的衬底上沉积 Ag 的单层 MoS2 的金属诱导局部应变的演变，即蓝宝石、SiO2/Si 和云母。MoS2 与蓝宝石之间的界面相互作用最强，而 MoS2 与云母之间的界面相互作用最弱。以 MoS2 拉曼峰的劈裂作为局部应变的指示，发现 Ag-MoS2 界面处的局部应变的演变行为很大程度上取决于衬底的界面相互作用。随着时间的推移，局部应变在蓝宝石上保存得最好，而在云母上则最容易松弛。密度泛函理论计算表明，不同衬底上 MoS2 的界面吸附能不同，表明单层 MoS2 与衬底之间的界面相互作用对应变演变至关重要。我们的工作有助于研究基于 TMDC 的器件的稳定性和可靠性，特别是对于柔性电子器件。
