Interfacial Study of Cubic Boron Nitride Films Deposited on Diamond

Monolayer Cubic Boron Nitride Terminated Diamond (111) Surfaces for Quantum Sensing and Electron Emission Applications

Monolayer cubic boron (B) nitride (N) terminated diamond (111) surfaces are proposed and investigated using density functional theory. The carbon (C)-N-B-terminated diamond (111) surface with a monolayer coverage of hydrogen and the C-N-B-terminated diamond (111) surface with a monolayer coverage of fluorine [named C-N-B-F-terminated (111) surface] have positive electron affinities (PEAs) with no inter-band gap states and nearly perfect alignment of nitrogen vacancy (NV). Thus, they could potentially be applied in NV-based quantum sensors. The C-B-N-terminated diamond (111) surface with a monolayer coverage of hydrogen [named C-B-N-H-terminated (111) surface], which has negative EAs (NEAs) and an adsorption energy of -3.51 eV, could potentially be employed in electron emission devices. Specifically, C-N-B-F- and C-B-N-H-terminated diamond (111) surfaces have the largest PEA (4.48 eV) and NEA (-4.00 eV), respectively, of any reported diamond surfaces. We also propose a formalism to construct multiple dipole structures on diamond surfaces to yield extremely large EAs.

Vacuum-Ultraviolet Photon Detections

Vacuum-ultraviolet (VUV) photon detection technology is an effective means for the exploration in the field of space science (monitoring the formation and evolution of solar storms), high-energy physics (dark matter detection), large-scale scientific facility (VUV free electron lasers) and electronic industry (high-resolution lithography). The advancement of this technology mainly depends on the performance optimization of VUV photodetectors. In this review, we introduced the research progress on the typical VUV photodetectors based on scintillator, photomultiplier tube, semiconductor, and gas, with their unique advantages and optimal performance indicators in different applications summarized. In particular, during recent years, thanks to the advances in ultra-wide bandgap semiconductors, economical VUV photodetectors with low power consumption and small size have been encouragingly developed. Finally, we pointed out the remaining challenges for each type of VUV detector, with the aim of maximizing the performance in a variety of applications in the future.

Improving Defect-Based Quantum Emitters in Silicon Carbide via Inorganic Passivation

Defect-based color centers in wide-bandgap crystalline solids are actively being explored for quantum information science, sensing, and imaging. Unfortunately, the luminescent properties of these emitters are frequently degraded by blinking and photobleaching that arise from poorly passivated host crystal surfaces. Here, a new method for stabilizing the photoluminescence and charge state of color centers based on epitaxial growth of an inorganic passivation layer is presented. Specifically, carbon antisite-vacancy pairs (CAV centers) in 4H-SiC, which serve as single-photon emitters at visible wavelengths, are used as a model system to demonstrate the power of this inorganic passivation scheme. Analysis of CAV centers with scanning confocal microscopy indicates a dramatic improvement in photostability and an enhancement in emission after growth of an epitaxial AlN passivation layer. Permanent, spatially selective control of the defect charge state can also be achieved by exploiting the mismatch in spontaneous polarization at the AlN/SiC interface. These results demonstrate that epitaxial inorganic passivation of defect-based quantum emitters provides a new method for enhancing photostability, emission, and charge state stability of these color centers.

Low-temperature solid state synthesis and in situ phase transformation to prepare nearly pure cBN

Cubic boron nitride (cBN) is synthesized by a low-temperature solid state synthesis and in situ phase transformation route with NH(4)BF(4), B, NaBH(4) and KBH(4) as the boron sources and NaN(3) as the nitrogen source. Furthermore, two new strategies are developed, i.e., applying pressure on the reactants during the reaction process and introducing the structural induction effect. These results reveal that the relative contents of cBN are greatly increased by applying these new strategies. Finally, almost pure cBN (∼90%) crystals are obtained by reacting NH(4)BF(4) and NaN(3) at 250 °C and 450 MPa for 24 h, with NaF as the structural induction material. The heterogeneous nucleation mechanism can commendably illuminate the structure induction effect of NaF with face center cubic structure. In addition, the induction effect results in the cBN nanocrystals presenting obvious oriented growth of {111} planes.