Department of Mechanical Engineering, Boston University , Boston, Massachusetts 02215 United States.
Department of Mechanical Engineering, University of Colorado , Boulder, Colorado 80309 United States.
Nano Lett. 2016 Sep 14;16(9):5836-41. doi: 10.1021/acs.nanolett.6b02615. Epub 2016 Aug 15.
We demonstrate the continuous and reversible tuning of the optical band gap of suspended monolayer MoS2 membranes by as much as 500 meV by applying very large biaxial strains. By using chemical vapor deposition (CVD) to grow crystals that are highly impermeable to gas, we are able to apply a pressure difference across suspended membranes to induce biaxial strains. We observe the effect of strain on the energy and intensity of the peaks in the photoluminescence (PL) spectrum and find a linear tuning rate of the optical band gap of 99 meV/%. This method is then used to study the PL spectra of bilayer and trilayer devices under strain and to find the shift rates and Grüneisen parameters of two Raman modes in monolayer MoS2. Finally, we use this result to show that we can apply biaxial strains as large as 5.6% across micron-sized areas and report evidence for the strain tuning of higher level optical transitions.
我们通过施加非常大的双轴应变，证明了悬空单层 MoS2 膜的光学带隙可以连续且可逆地调节多达 500meV。通过使用化学气相沉积（CVD）生长对气体几乎不可渗透的晶体，我们能够在悬空膜上施加压差以产生双轴应变。我们观察了应变对光致发光（PL）光谱中峰的能量和强度的影响，并发现光学带隙的线性调节速率为 99meV/%。然后，我们使用该方法研究应变下双层和三层器件的 PL 光谱，并找到单层 MoS2 中两个 Raman 模式的位移率和 Grüneisen 参数。最后，我们利用这一结果表明，我们可以在微米级区域施加高达 5.6%的双轴应变，并报告了更高阶光学跃迁的应变调谐的证据。
