Precise control of the interlayer twist angle in large scale MoS2 homostructures

Abstract

Twist angle between adjacent layers of two-dimensional (2D) layered materials provides an exotic degree of freedom to enable various fascinating phenomena, which opens a research direction-twistronics. To realize the practical applications of twistronics, it is of the utmost importance to control the interlayer twist angle on large scales. In this work, we report the precise control of interlayer twist angle in centimeter-scale stacked multilayer MoS 2 homostructures via the combination of wafer-scale highly-oriented monolayer MoS 2 growth techniques and a water-assisted transfer method. We confirm that the twist angle can continuously change the indirect bandgap of centimeter-scale stacked multilayer MoS 2 homostructures, which is indicated by the photoluminescence peak shift. Furthermore, we demonstrate that the stack structure can affect the electrical properties of MoS 2 homostructures, where 30°twist angle yields higher electron mobility. Our work provides a firm basis for the development of twistronics.

Probing stacking configurations in a few layered MoS2 by low frequency Raman spectroscopy

“…3 (e), all the other areas except the two-layered regions are shown in white color. It should be noted that for twisted bilayers, the shear mode disappears when the twist angle is between 4—40 degrees 5 , 44 . In such a case, the twist angle range can be roughly estimated by the lack of shear mode and the frequency of breathing mode.…”

“…For instance, bilayer graphene can be transformed into a gate-tunable superconductor or into an insulator by choosing the right twist angle between the layers 4 . It is also reported that in multilayered MoS 2 , the twist angle between the layers can change the indirect bandgap 5 . Another example is the presence of a stacking-dependent symmetry variation that leads to valley polarization, which can be utilized for valleytronics applications 6 .…”

“…The dependence of low-frequency modes on the number of layers was first reported in a few-layered graphene in 2012 37 . This was followed by various reports, which used the low-frequency modes to determine the number of layers [38][39][40][41] , to identify the twist angle between the layers and various stacking configurations 5,[42][43][44][45][46][47] , to probe interlayer coupling 48,49 and to determine the crystal orientation in various 2D materials and in van der Waals heterostructures 50,51 . The development of this research over the last few years indicates the ability of the low-frequency modes to characterize a wide range of 2D materials, including van der Waals heterostructures.…”

“…However, no extensive studies of the low-frequency modes to probe the stacking configurations of MoS 2 are reported so far. Previous studies that probed stacking configuration in MoS 2 had relied only on single point spectroscopic measurements of Raman modes 5,44,[52][53][54] . While single point Raman measurements are sufficient to measure the properties of a homogenous sample, they do not provide an accurate picture about the distribution of any physical properties, such as the stacking configurations, within the MoS 2 sample.…”

Electrical band flattening, valley flux, and superconductivity in twisted trilayer graphene

“…However, exploring unconventional states of matter requires identifying systems where electronic correlations, topology, and electronic dispersions can be realistically controlled. In this regard, twisted van der Waals materials [1][2][3][4][5][6][7][8] provide a powerful solid state platform to realize exotic quantum phenomena. The tunability of twisted van der Waals materials stems from the emergence of a band structure that can be controlled by the twist between different two-dimensional materials [9,10].…”