Enhanced ultraviolet absorption in BN monolayers caused by tunable buckling

The optical properties of a hexagonal Boron Nitride, BN, monolayer across the UV spectrum are studied by tuning its planar buckling. The strong o --o-bond through sp2 hybridization of a flat BN monolayer can be changed to a stronger o--ir bond through sp3 hybridization by increasing the planar buckling. This gives rise to the s- and p-orbital contributions to form a density of states around the Fermi energy, and these states dislocate to a lower energy in the presence of an increased planar buckling. Consequently, the wide band gap of a flat BN monolayer is reduced to a smaller band gap in a buckled BN monolayer enhancing its optical activity in the Deep-UV region. The optical properties such as the dielectric function, the reflectivity, the absorption, and the optical conductivity spectra are investigated. It is shown that the absorption rate can be enhanced by approximate to 15% for intermediate values of planar buckling in the Deep-UV region, and approximate to 20% at higher values of planar buckling in the near-UV region. Furthermore, the optical conductivity is enhanced by increased planar buckling in both the visible and the Deep-UV regions depending on the direction of the polarization of the incoming light. Our results may be useful for optoelectronic BN monolayer devices in the UV range including UV spectroscopy, deep-UV communications, and UV photodetectors.