Middle-infrared optical analysis of BN thin films synthesised by pulsed laser deposition from experimental and theoretical calculations insights

Hexagonal boron nitride (hBN) films have received increasing attention because of their excellent optical properties, especially their broad transmittance spectrum from visible to infrared wavelengths. However, the fundamental optical properties of hBN in the middle-infrared range have not been thoroughly investigated. Here, a series of hBN thin films was deposited using an excimer laser in an ultra-high vacuum chamber, and the in-fluence of the laser pulse energies on the optical constants of hBN in the infrared range was explored. Inter-estingly, these as-prepared BN films could be inevitably detected a few of hydroxyl groups on the surfaces. Further calculations based on density functional theory (DFT) proved that some hydroxyl groups had weak ef-fects on the electronic and optical performance of the OH-BN bilayers model. According to the experimental and simulation results, the estimated refractive index of these BN films showed normal dispersion with variations from 2.15 to 2.35 in a broad wavelength range. Accurate optical parameters could provide a highly precise design of hBN-based infrared windows for infrared detectors.