Manipulation of Optical and Mechanical Properties of Cubic Boron Nitride by Defect Engineering under Pressure

Incorporation of defects into covalent solids (e.g., diamond) can greatly alter their electronic and structural properties for creating optically active color centers, which also leads to largely adjusted mechanical properties. As an electronic equivalent to diamond, cubic boron nitride (cBN) with superhardness is often formed with crystalline imperfections. However, the defect dependences of color centers and mechanical properties in cBN have been rarely explored due to the difficulties in synthesizing defective crystals with controllable defects, which have largely limited its functionality. In this work, we present a systematic study of various defective cBN crystals prepared from different catalyst systems under high pressure with a focus on the optical and mechanical properties. A number of distinct color centers have been identified for emitting luminescence across a broad spectrum of lights, ranging from infrared to ultraviolet. Because of the defects, the hardness of cBN crystals can also be largely tuned in a wide range of 43–63 GPa. These findings offer important foundations for rationally tailoring the optical and mechanical properties of diamond-like covalent solids by defect chemistry.