Thickness identification of 2D hexagonal boron nitride thin flakes by optical imaging in dry transfer method

Hexagonal Boron Nitride (h-BN) thin flake plays an important role in 2D materials device fabrication process. Enhancing the efficiency of searching and transferring thin h-BN flakes has great significance in nanotechnology. In this paper, we investigated the optical contrast of thin h-BN flakes in the PMMA/PMGI transfer method process by simulation to analyze the influence of the thickness of PMMA, PMGI and SiO2 layers and the wavelength of incident light beam on the optical contrast of thin h-BN flakes and achieved the optimal structure of the thin film system for searching thin h-BN flakes. Furthermore, the optical contrasts of thin h-BN flakes were experimentally observed on PMMA/PMGI/Si substrate and compared with the results of simulation. The values of optical contrast we got from the simulation were in accordance with the experimental findings. This work will help to boost the enhancement of speed and efficiency in searching and transferring thin h-BN flakes in 2D materials research.