Rhombohedral Boron Nitride for Deep UV Nonlinear Spectroscopy
Seung Tae Kim
Kyung Hee University, Seoul, Republic of Korea _______________________________________
Rhombohedral boron nitride (rBN) is a polytype of boron nitride with a rhombohedral crystal structure, characterized by layer sliding and inversion symmetry breaking. These structural properties enhance its nonlinear optical response, making rBN highly efficient in second harmonic generation (SHG). In this study, we investigate the deep ultraviolet (DUV) photoluminescence (PL) characteristics at cryogenic temperatures and the SHG properties at room temperature in rBN containing carbon defects, using a femtosecond laser. SHG measurements with an femtosecond laser reveal a strong nonlinear response with a quadratic dependence on laser power. Additionally, a six-fold rotational symmetry is observed due to the crystal structure, and the SHG intensity is several orders of magnitude higher than that of hexagonal boron nitride (hBN). DUV PL measurements using a 193 nm (6.42 eV) femtosecond laser show that rBN exhibits broader emission linewidths in similar energy range to hBN. Furthermore, carbon-related emission experiences a blue-shifted peak due to layer sliding effect in rBN.
Email: kstphysics@khu.ac.kr