Many advanced applications of diamond materials are now being limited by unknown surface defects, including in the fields of high power/frequency electronics and quantum computing and quantum sensing. Of acute interest to diamond researchers worldwide is the loss of quantum coherence in near‐surface nitrogen‐vacancy (NV) centers and the generation of associated magnetic noise at the diamond surface. Here for the first time is presented the observation of a family of primal diamond surface defects, which is suggested as the leading cause of band‐bending and Fermi‐pinning phenomena in diamond devices. A combination of density functional theory and synchrotron‐based X‐ray absorption spectroscopy is used to show that these defects introduce low‐lying electronic trap states. The effect of these states is modeled on band‐bending into the diamond bulk and it is shown that the properties of the important NV defect centers are affected by these defects. Due to the paramount importance of near‐surface NV center properties in a growing number of fields, the density of these defects is further quantified at the surface of a variety of differently‐treated device surfaces, consistent with best‐practice processing techniques in the literature. The identification and characterization of these defects has wide‐ranging implications for diamond devices across many fields.
Adjoint-optimized nanoscale light extractor for nitrogen-vacancy centers in diamond
Abstract We designed a nanoscale light extractor (NLE) for the efficient outcoupling and beaming of broadband light emitted by shallow, negatively charged nitrogen-vacancy (NV) centers in bulk diamond. The NLE consists of a patterned silicon layer on diamond and requires no etching of the diamond surface. Our design process is based on adjoint optimization using broadband time-domain simulations and yields structures that are inherently robust to positioning and fabrication errors. Our NLE functions like a transmission antenna for the NV center, enhancing the optical power extracted from an NV center positioned 10 nm below the diamond surface by a factor of more than 35, and beaming the light into a ±30° cone in the far field. This approach to light extraction can be readily adapted to other solid-state color centers.
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- Award ID(s):
- 1839174
- NSF-PAR ID:
- 10294664
- Date Published:
- Journal Name:
- Nanophotonics
- Volume:
- 10
- Issue:
- 1
- ISSN:
- 2192-8606
- Page Range / eLocation ID:
- 393 to 401
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Color-center–hosting semiconductors are emerging as promising source materials for low-field dynamic nuclear polarization (DNP) at or near room temperature, but hyperfine broadening, susceptibility to magnetic field heterogeneity, and nuclear spin relaxation induced by other paramagnetic defects set practical constraints difficult to circumvent. Here, we explore an alternate route to color-center–assisted DNP using nitrogen-vacancy (NV) centers in diamond coupled to substitutional nitrogen impurities, the so-called P1 centers. Working near the level anticrossing condition—where the P1 Zeeman splitting matches one of the NV spin transitions—we demonstrate efficient microwave-free 13 C DNP through the use of consecutive magnetic field sweeps and continuous optical excitation. The amplitude and sign of the polarization can be controlled by adjusting the low-to-high and high-to-low magnetic field sweep rates in each cycle so that one is much faster than the other. By comparing the 13 C DNP response for different crystal orientations, we show that the process is robust to magnetic field/NV misalignment, a feature that makes the present technique suitable to diamond powders and settings where the field is heterogeneous. Applications to shallow NVs could capitalize on the greater physical proximity between surface paramagnetic defects and outer nuclei to efficiently polarize target samples in contact with the diamond crystal.more » « less
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Abstract The nitrogen-vacancy (NV) color center in diamond has rapidly emerged as an important solid-state system for quantum information processing. Whereas individual spin registers have been used to implement small-scale diamond quantum computing, the realization of a large-scale device requires the development of an on-chip quantum bus for transporting information between distant qubits. Here, we propose a method for coherent quantum transport of an electron and its spin state between distant NV centers. Transport is achieved by the implementation of spatial stimulated adiabatic Raman passage through the optical control of the NV center charge states and the confined conduction states of a diamond nanostructure. Our models show that, for two NV centers in a diamond nanowire, high-fidelity transport can be achieved over distances of order hundreds of nanometers in timescales of order hundreds of nanoseconds. Spatial adiabatic passage is therefore a promising option for realizing an on-chip spin quantum bus.more » « less
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The application of color centers in wide-bandgap semiconductors to nanoscale sensing and quantum information processing largely rests on our knowledge of the surrounding crystalline lattice, often obscured by the countless classes of point defects the material can host. Here, we monitor the fluorescence from a negatively charged nitrogen-vacancy (NV − ) center in diamond as we illuminate its vicinity. Cyclic charge state conversion of neighboring point defects sensitive to the excitation beam leads to a position-dependent stream of photo-generated carriers whose capture by the probe NV − leads to a fluorescence change. This “charge-to-photon” conversion scheme allows us to image other individual point defects surrounding the probe NV, including nonfluorescent “single-charge emitters” that would otherwise remain unnoticed. Given the ubiquity of color center photochromism, this strategy may likely find extensions to material systems other than diamond.more » « less
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Solid-state laser refrigeration of semiconductors remains an outstanding experimental challenge. In this work, we show that, following excitation with a laser wavelength of 532 nm, bulk diamond crystals doped with H3 centers both emit efficient up-conversion (anti-Stokes) photoluminescence and also show significantly reduced photothermal heating relative to crystals doped with nitrogen–vacancy (NV) centers. The H3 center in diamond is a highly photostable defect that avoids bleaching at high laser irradiances of 10–70 MW/cm[Formula: see text] and has been shown to exhibit laser action, tunable over the visible band of 500–600 nm. The observed reduction of photothermal heating arises due to a decrease in the concentration of absorbing point defects, including NV-centers. These results encourage future exploration of techniques for H3 enrichment in diamonds under high-pressure, high-temperature conditions for the simultaneous anti-Stokes fluorescence cooling and radiation balanced lasing in semiconductor materials. Reducing photothermal heating in diamond through the formation of H3 centers also opens up new possibilities in quantum sensing via optically detected magnetic resonance spectroscopy at ambient conditions.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1515/nanoph-2020-0387
