Hexagonal boron nitride (h-BN). In-plane refractive index (ordinary ray, no). h-BN flakes of thickness around 1000 nm were mechanically exfoliated from a bulk crystal and transferred onto quartz substrates for transmission measurements. The single oscillator model is used to fit transmission spectra of several hBN flakes of different thickness.
Boron nitride (BN) is a versatile material that exists in various structural forms, each with distinct physical and chemical properties. The two most notable allotropes are hexagonal boron nitride (h-BN) and cubic boron nitride (c-BN). Hexagonal BN resembles the structure of graphite and is often used as a lubricant and an insulator due to its excellent thermal stability and chemical resistance. It is also transparent to ultraviolet and deep ultraviolet light, which makes it useful in optical applications. Cubic BN, on the other hand, has a structure similar to that of diamond and exhibits extraordinary hardness, second only to diamond itself. It is used in high-pressure applications and as an abrasive material. Both forms have high thermal conductivity and are chemically stable, making them suitable for a variety of high-temperature applications. Boron nitride can be synthesized using methods such as chemical vapor deposition (CVD), and its properties can be tuned via doping or alloying with other materials. Overall, the diverse structural forms and resultant properties of boron nitride make it a material of significant interest for a wide array of applications, from electronics to cutting tools and optical devices.