Department of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
ACS Nano. 2013 Aug 27;7(8):7126-31. doi: 10.1021/nn4024834. Epub 2013 Jul 12.
Tuning band energies of semiconductors through strain engineering can significantly enhance their electronic, photonic, and spintronic performances. Although low-dimensional nanostructures are relatively flexible, the reported tunability of the band gap is within 100 meV per 1% strain. It is also challenging to control strains in atomically thin semiconductors precisely and monitor the optical and phonon properties simultaneously. Here, we developed an electromechanical device that can apply biaxial compressive strain to trilayer MoS2 supported by a piezoelectric substrate and covered by a transparent graphene electrode. Photoluminescence and Raman characterizations show that the direct band gap can be blue-shifted for ~300 meV per 1% strain. First-principles investigations confirm the blue-shift of the direct band gap and reveal a higher tunability of the indirect band gap than the direct one. The exceptionally high strain tunability of the electronic structure in MoS2 promising a wide range of applications in functional nanodevices and the developed methodology should be generally applicable for two-dimensional semiconductors.
通过应变工程来调节半导体的能带能量，可以显著提高其电子、光子和自旋电子性能。尽管低维纳米结构相对灵活，但报道的带隙可调谐性在每 1%应变下约为 100 毫电子伏特。精确控制原子层厚度半导体中的应变并同时监测光学和声子性质也是具有挑战性的。在这里，我们开发了一种机电设备，可以在由压电衬底支撑并覆盖透明石墨烯电极的三层 MoS2 上施加双轴压缩应变。光致发光和拉曼特性表明，直接带隙可以通过每 1%应变约 300 毫电子伏特的蓝移来实现。第一性原理研究证实了直接带隙的蓝移，并揭示了间接带隙的可调谐性高于直接带隙。MoS2 中电子结构的异常高应变可调谐性有望在功能纳米器件中得到广泛应用，所开发的方法应该普遍适用于二维半导体。
