Blue-light-emitting color centers in high-quality hexagonal boron nitride

Light emitters in wide band gap semiconductors are of great fundamental\ninterest and have potential as optically addressable qubits. Here we describe\nthe discovery of a new color center in high-quality hexagonal boron nitride\n(h-BN) with a sharp emission line at 435 nm. The emitters are activated and\ndeactivated by electron beam irradiation and have spectral and temporal\ncharacteristics consistent with atomic color centers weakly coupled to lattice\nvibrations. The emitters are conspicuously absent from commercially available\nh-BN and are only present in ultra-high-quality h-BN grown using a\nhigh-pressure, high-temperature Ba-B-N flux/solvent, suggesting that these\nemitters originate from impurities or related defects specific to this unique\nsynthetic route. Our results imply that the light emission is activated and\ndeactivated by electron beam manipulation of the charge state of an\nimpurity-defect complex.\n