Enhancement of the contrast for a hexagonal boron nitride monolayer placed on a silicon nitride/silicon substrate

We propose a visualization technique for identifying an exfoliated monolayer hexagonal boron nitride (hBN) flake placed on a SiN x /Si substrate. The use of a Si substrate with a 63 nm thick SiN x film enhanced the contrast of monolayer hBN at wavelengths of 480 and 530 nm by up to 12% and -12%, respectively. The maximum contrast for the Si substrate with SiN x is more than four times as large as that for a Si substrate with a similar to 90 or similar to 300 nm SiO2 film. Based on the results of the reflectance spectrum measurement and numerical calculations, the enhancement is discussed.