Das Subhadip, Prasad Suchitra, Chakraborty Biswanath, Jariwala Bhakti, Shradha Sai, Muthu D V S, Bhattacharya Arnab, Waghmare U V, Sood A K
Department of Physics, Indian Institute of Science, Bangalore 560012, India.
Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India.
Nanoscale. 2021 Jan 21;13(2):1248-1256. doi: 10.1039/d0nr06583h.
In the bilayer ReS2 channel of a field-effect transistor (FET), we demonstrate using Raman spectroscopy that electron doping (n) results in softening of frequency and broadening of linewidth for the in-plane vibrational modes, leaving the out-of-plane vibrational modes unaffected. The largest change is observed for the in-plane Raman mode at ∼151 cm-1, which also shows doping induced Fano resonance with the Fano parameter 1/q = -0.17 at a doping concentration of ∼3.7 × 1013 cm-2. A quantitative understanding of our results is provided by first-principles density functional theory (DFT), showing that the electron-phonon coupling (EPC) of in-plane modes is stronger than that of out-of-plane modes, and its variation with doping is independent of the layer stacking. The origin of large EPC is traced to 1T to 1T' structural phase transition of ReS2 involving in-plane displacement of atoms whose instability is driven by the nested Fermi surface of the 1T structure. Results are compared with those of the isostructural trilayer ReSe2.
在场效应晶体管（FET）的双层ReS2沟道中，我们利用拉曼光谱证明，电子掺杂（n）会导致面内振动模式的频率软化和线宽展宽，而面外振动模式不受影响。在~151 cm-1处的面内拉曼模式观察到最大变化，在掺杂浓度约为3.7×1013 cm-2时，该模式还显示出掺杂诱导的法诺共振，法诺参数1/q = -0.17。第一性原理密度泛函理论（DFT）对我们的结果进行了定量理解，表明面内模式的电子-声子耦合（EPC）比面外模式更强，并且其随掺杂的变化与层堆叠无关。大EPC的起源可追溯到ReS2的1T到1T'结构相变，该相变涉及原子的面内位移，其不稳定性由1T结构的嵌套费米面驱动。将结果与同构的三层ReSe2的结果进行了比较。
