Shaanxi Joint Lab of Graphene, State Key Lab Incubation Base of Photoelectric Technology and Functional Materials, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics and Photon-Technology, Northwest University , Xi'an 710069, China.
ACS Appl Mater Interfaces. 2017 Feb 8;9(5):4956-4965. doi: 10.1021/acsami.6b13961. Epub 2017 Jan 30.
Surface optical rectification was observed from the layered semiconductor molybdenum disulfide (MoS) crystal via terahertz (THz) time-domain surface emission spectroscopy under linearly polarized femtosecond laser excitation. The radiated THz amplitude of MoS has a linear dependence on ever-increasing pump fluence and thus quadratic with the pump electric field, which discriminates from the surface Dember field induced THz radiation in InAs and the transient photocurrent-induced THz generation in graphite. Theoretical analysis based on space symmetry of MoS crystal suggests that the underlying mechanism of THz radiation is surface optical rectification under the reflection configuration. This is consistent with the experimental results according to the radiated THz amplitude dependences on azimuthal and incident polarization angles. We also demonstrated the damage threshold of MoS due to microscopic bond breaking under the femtosecond laser irradiation, which can be monitored via THz time-domain emission spectroscopy and Raman spectroscopy.
通过太赫兹（THz）时域表面发射光谱，在飞秒激光激发下，观察到层状半导体二硫化钼（MoS）晶体的表面光整流。MoS 发出的太赫兹幅度与泵浦光强呈线性关系，与泵浦电场呈二次方关系，这与 InAs 中表面 Dember 场诱导的太赫兹辐射和石墨中瞬态光电流诱导的太赫兹产生不同。基于 MoS 晶体空间对称性的理论分析表明，太赫兹辐射的潜在机制是反射配置下的表面光整流。这与根据太赫兹辐射幅度对方位角和入射偏振角的依赖关系的实验结果一致。我们还通过太赫兹时域发射光谱和拉曼光谱证明了 MoS 在飞秒激光照射下由于微观键断裂而产生的损伤阈值，可通过太赫兹时域发射光谱和拉曼光谱进行监测。
