Liu Yue,Zhou Yu,Zhang Hao,Ran Feirong,Zhao Weihao,Wang Lin,Pei Chengjie,Zhang Jindong,Huang Xiao,Li Hai
Interlayer interactions at the heterointerfaces of van der Waals heterostructures (vdWHs), which consist of vertically stacked two-dimensional materials, play important roles in determining their properties. The interlayer interactions are tunable from noncoupling to strong coupling by controlling the twist angle between adjacent layers. However, the influence of stacking sequence and individual component thickness on the properties of vdWHs has rarely been explored. In this work, the influence of the stacking sequence of WSe 2 and graphene in vdWHs of graphene-on-WSe 2 (graphene/WSe 2 ) or WSe 2 -on-graphene (WSe 2 /graphene), as well as their thickness, on their interlayer interaction was systematically investigated by ultralow-frequency (ULF) Raman spectroscopy. A series of ULF breathing modes of WSe 2 nanosheets in these vdWHs were observed with frequencies highly dependent on graphene thickness. Interestingly, the ULF breathing modes of WSe 2 red-shifted in graphene/WSe 2 and WSe 2 /graphene configurations, and the amount of shift in the former was much larger than that in the latter. In contrast, no obvious ULF shift was observed by varying the twist angle between WSe 2 and graphene. This indicates that the interlayer interaction is more sensitive to the stacking sequence compared with the twist angle. The results provide alternative approaches to modulate the interlayer interaction of vdWHs and, thus, tune their optical and optoelectronic properties.
Ting Sai,Pengfei Wang,Xiaoying Gu,Xueping Xu,Jinji Sun,Jing Ye
Cobalt-based amorphous alloys (Co-MG) demonstrate ultra-high permeability and remarkably-low power loss, positioning them as promising candidates for shielding (near-) static magnetic fields and addressing accuracy limitations in extremely-weak magnetic measurements. However , the brittleness and poor understanding about magnetic performance below 100 Hz have impeded their widespread adoption. To integrate satisfied processing, magnetic and mechanical performances, polystyrene-grafted Co-MG composites are developed. Compared with permalloy-1J85, Co-MG-( g -PS_35 %) composite exhibits 40 % increase in initial permeability, 48 % increase in saturation magnetization, 71 % reduction in remanence within shielding area. In contrast to Mn–Zn ferrite, Co-MG-( g -PS_35 %) composite demonstrates the power loss and μ ″/ μ ′ 2 values lower by an order of magnitude, resulting in magnetic noises 85 % lower at 1 Hz. Furthermore, the resultant composite maintains similar processing-rheological behaviors and mechanical properties compared with bulk polystyrene. It provides an innovative solution to expand real-world applications for biomagnetic detection, and overcome the sensitivity limitation of extremely-weak magnetic measurement.
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