Strain and Charge Doping Fingerprints of the Strong Interaction between Monolayer MoS₂ and Gold

Abstract

Gold-mediated exfoliation of MoS 2 has recently attracted considerable interest. The strong interaction between MoS 2 and Au facilitates preferential production of centimeter-sized monolayer MoS 2 with near-unity yield and provides a heterostructure system noteworthy from a fundamental standpoint. However, little is known about the detailed nature of the MoS 2 –Au interaction and its evolution with the MoS 2 thickness. Here, we identify the specific vibrational and binding energy fingerprints of this interaction using Raman and X-ray photoelectron spectroscopy, which indicate substantial strain and charge doping in monolayer MoS 2 . Tip-enhanced Raman spectroscopy reveals heterogeneity of the MoS 2 –Au interaction at the nanoscale, reflecting the spatial nonconformity between the two materials. Micro-Raman spectroscopy shows that this interaction is strongly affected by the roughness and cleanliness of the underlying Au. Our results elucidate the nature of the MoS 2 –Au interaction and guide strain and charge doping engineering of MoS 2 .

Spectroscopic Ellipsometry Investigation of Au‐Assisted Exfoliated Large‐Area Single‐Crystalline Monolayer MoS2

“…This is different from the cases of 1L MoS 2 on Ag and Pt films, [22,43] which implies uniform strain distribution in MoS 2 caused by regular Au clustering. As for the out-of-plane vibration A 1g mode at 402.8 cm À1 , it splits into two peaks located at 395.6 and 402.6 cm À1 , which is consistent with the observation of Velický et al [22,44] The higher frequency peak of the A 1g mode of 1L MoS 2 on Au is almost identical to that on SiO 2 /Si (approximately regarded as the corresponding Raman frequency of bare 1L MoS 2 ), indicating that there may be regions where the 1L MoS 2 is not in direct contact with Au. [44] The lower frequency of the A 1g mode is mainly caused by the charge in the 1L MoS 2 transferred from Au in intimate contact as the A 1g mode possesses a strong doping dependence.…”

Thermal expansion coefficient of few-layer MoS2 studied by temperature-dependent Raman spectroscopy

“…In our work, no additional peak was observed in the spectrum for supported 2L MoS 2 , suggesting that the strain is the dominant effect rather than defects. The E 2g mode of monolayer MoS 2 has been demonstrated to split into two singlets as the external strain is increased 42 , 43 . As presented in Fig.…”

FeSi2: a two-dimensional ferromagnet containing planar hexacoordinate Fe atoms

“…The method of preparing a 2D thin lm by using the strong interaction between the lm and substrate has been widely used in experiments. [57][58][59][60][61] For future experimental identication, we also simulated the STM image of the FeSi 2 monolayer on the Si (110) surface. The bright areas in the simulated STM image are associated with Fe atoms (see the labels in Fig.…”