Control of biaxial strain in single-layer molybdenite using local thermal expansion of the substrate
Control of biaxial strain in single-layer molybdenite using local thermal expansion of the substrate
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DOI：
10.1088/2053-1583/2/1/015006
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发表时间：
2015-03-01
期刊：
影响因子：
5.5
通讯作者：
Korn, Tobias
中科院分区：
文献类型：
--
作者：
Plechinger, Gerd;Castellanos-Gomez, Andres;Korn, Tobias
单层MoS2是一种直接带隙半导体，其电子能带结构强烈依赖于施加到其晶格的应变。虽然单轴应变可以很容易地以受控方式施加，例如通过弯曲顶部有原子薄 MoS2 层的柔性基板，但双轴应变的实验实现更具挑战性。在这里，我们利用 MoS2 和硅基基底的热膨胀系数之间的巨大不匹配，通过用聚焦激光加热基底来施加可控的双轴拉伸应变。这种双轴应变的影响可以在光谱中直接观察到，表现为 MoS2 光致发光的红移。我们还展示了该方法通过在基板上采用高吸收性特征来设计更复杂的应变模式以实现不均匀的热分布的潜力。通过将观察到的红移与应变相关的能带结构计算进行比较，我们估计硅基基底施加的双轴应变高达 0.2%，对应于每百分比双轴拉伸应变 105 meV 的带隙调制。
Single-layer MoS2 is a direct-gap semiconductor whose electronic band structure strongly depends on the strain applied to its crystal lattice. While uniaxial strain can be easily applied in a controlled way, e.g., by bending of a flexible substrate with the atomically thin MoS2 layer on top, experimental realization of biaxial strain is more challenging. Here, we exploit the large mismatch between the thermal expansion coefficients of MoS2 and a silicone-based substrate to apply a controllable biaxial tensile strain by heating the substrate with a focused laser. The effect of this biaxial strain is directly observable in optical spectroscopy as a redshift of the MoS2 photoluminescence. We also demonstrate the potential of this method to engineer more complex strain patterns by employing highly absorptive features on the substrate to achieve non-uniform heat profiles. By comparison of the observed redshift to strain-dependent band structure calculations, we estimate the biaxial strain applied by the silicone-based substrate to be up to 0.2%, corresponding to a band gap modulation of 105 meV per percentage of biaxial tensile strain.