Strain-induced band evolution in lateral transition metal dichalcogenides heterostructures

• Main Authors: Wang, Dean, 王鼎
• Other Authors: Chang, Wen-Hao
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/32268349752817149661

碩士 === 國立交通大學 === 電子物理系所 === 105 === Semiconductor heterostructures based on two-dimensional transition metal dichalcogenides (TMDs) have attracted great interests recently. These two-dimensional heterostructures were given hopes for the future flexible optoelectronic devices due to their unique structural and optical properties. In these heterostructrues, the outer material usually exhibits serious strain variation caused by large lattice mismatch, i.e., ~1.59% variation has been observed in the MoS2-WSe2 system. In this work, the spatial inhomogeneity in lateral MoS2-WSe2 and WSe2-MoSe2 heterostructures were investigated by spatial-resolved photoluminescence (PL), showing strong correlated PL intensity and energy. The PL correlation is found to be caused by carrier occupation between different valleys, which can be described by the Boltzmann distribution. After analyzing by model, the band parameters including energy difference and ratio of deformation potential for involved valleys can be determined. Finally, we demonstrated the strain-free MoS2 and WSe2 monolayers are direct and indirect semiconductors, respectively. Our work presented here provides not only the important band parameters but also information on the lateral heterostructures. Particularly, the local strain variation could result in not only the small change of band gap energy but also the great change of direct/indirect gap, which could largely impact the device properties for future planar TMD heterostructures.