posted on 2023-07-26, 13:40authored byBaoqing Zhang, Zihao Zhang, Hecheng Han, Haotian Ling, Xijian Zhang, Yiming Wang, Qingpu Wang, Hu Li, Yifei Zhang, Jiawei Zhang, Aimin Song
Two-dimensional (2D) materials possess unique properties
primarily
due to the quantum confinement effect, which highly depends on their
thicknesses. Identifying the number of atomic layers in these materials
is a crucial, yet challenging step. However, the commonly used optical
reflection method offers only very low contrast. Here, we develop
an approach that shows unprecedented sensitivity by analyzing the
brightness of dark-field optical images. The brightness of the 2D
material edges has a linear dependence on the number of atomic layers.
The findings are modeled by Rayleigh scattering, and the results agree
well with the experiments. The relative contrast of single-layer graphene
can reach 70% under white-light incident conditions. Furthermore,
different 2D materials were successfully tested. By adjusting the
exposure conditions, we can identify the number of atomic layers ranging
from 1 to over 100. Finally, this approach can be applied to various
substrates, even transparent ones, making it highly versatile.