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Acoustic wave transparency in nitrogen-vacancy centers in a photonic crystal
摘要： We show that the interaction of nitrogen-vacancy centers in diamond with a strain field in a photonic crystal can lead to acoustic wave transparency. This occurs due to the strong interaction of photons with the modified photonic reservoir near the photonic band edge created by the photonic crystal. For achieving this, we explore the properties of the spin states of the ground state of the nitrogen-vacancy centers, where one transition interacts with a strain field while the other transition has spontaneous emission that occurs near the edge of the photonic band gap, which should be in the microwave regime. We show that depending on the form of the photonic density of states acoustic wave transparency is obtained at one or two frequencies.
关键词： Induced transparency,Photonic crystal,Non-Markovian dynamics,Acoustic field,Nitrogen-vacancy center in diamond
更新于2025-09-19 17:15:36
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The study of low temperature irradiation induced defects in p-Si using deep-level transient spectroscopy
摘要： Primary defects introduced in boron-doped silicon by an alpha-particle source with a fluence rate of 7 × 106 cm?2 s?1 at cryogenic temperatures were investigated using deep-level transient spectroscopy (DLTS). The data showed that the defects observed between 35 K and 120 K were not detectable when irradiation was carried out at room temperature. The defect levels were observed at 0.10 eV, 0.14 eV and 0.18 eV above the valence band maximum. These levels were attributed to the boron-substitutional vacancy complex, the mono vacancy and a vacancy-related defect respectively.
关键词： Irradiation,DLTS,Silicon,Vacancy
更新于2025-09-19 17:15:36
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Structural micro-modulation on Bi3+ doped Ba2Ga2GeO7 phosphor with considerable tunability of the defect-oriented optical properties
摘要： We report a new Ba2Ga2GeO7:Bi3+ phosphor with broad emission almost covers the entire visible area generated from different bismuth emission centers in crystalline structure. The two peaks positions are invariably located at 497 and 611 nm which were independently excited by 365 and 387 nm excitation sources. As the emission tightly relies on the excitation source in an extremely wide range (260 to 470 nm), the emission color can be easily manipulated from cyan to red. The WLEDs devices with Ra = 90.40 and 91.98 were fabricated by employing Ba2Ga2GeO7:0.012Bi3+ as a red component phosphor. Through analyzing, we found P2 (Ga/Ge) sites tend to form vacancies in the sintering process. When bismuth concentration is set fixed, the luminescent intensity is quite dependent on the quantity of Ga or Ge vacancies which are beneficial to form Bi3+ emission centers and provide a fresh idea for structural micro-modulation. Our results also provide new insights for understanding the roles of the vacancy played in phosphors.
关键词： luminescence,bismuth,color-tunable,WLEDs,phosphor,vacancy
更新于2025-09-19 17:15:36
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Apparent delocalization of the current density in metallic wires observed with diamond nitrogen-vacancy magnetometry
摘要： We report on a quantitative analysis of the magnetic field generated by a continuous current running in metallic microwires fabricated on an electrically insulating diamond substrate. A layer of nitrogen-vacancy (NV) centers engineered near the diamond surface is employed to obtain spatial maps of the vector magnetic field, by measuring Zeeman shifts through optically detected magnetic resonance spectroscopy. The in-plane magnetic field (i.e., parallel to the diamond surface) is found to be significantly weaker than predicted, while the out-of-plane field also exhibits an unexpected modulation. We show that the measured magnetic field is incompatible with Ampère’s circuital law or Gauss’s law for magnetism when we assume that the current is confined to the metal, independent of the details of the current density. This result was reproduced in several diamond samples, with a measured deviation from Ampère’s law by as much as 94(6)% (i.e., a 15σ violation). To resolve this apparent magnetic anomaly, we introduce a generalized description whereby the current is allowed to flow both above the NV sensing layer (including in the metallic wire) and below the NV layer (i.e., in the diamond). Inversion of the Biot-Savart law within this two-channel description leads to a unique solution for the two current densities that completely explains the data, is consistent with the laws of classical electrodynamics, and indicates a total NV-measured current that closely matches the electrically measured current. However, this description also leads to the surprising conclusion that in certain circumstances the majority of the current appears to flow in the diamond substrate rather than in the metallic wire, and to spread laterally in the diamond by several micrometers away from the wire. No electrical conduction was observed between nearby test wires, ruling out a conventional conductivity effect. Moreover, the apparent delocalization of the current into the diamond persists when an insulating layer is inserted between the metallic wire and the diamond or when the metallic wire is replaced by a graphene ribbon. The possibilities of a measurement error, a problem in the data analysis, or a current-induced magnetization effect are discussed, but do not seem to offer a more plausible explanation for the effect. Understanding and mitigating this apparent anomaly will be crucial for future applications of NV magnetometry to charge transport studies.
关键词： diamond magnetometry,nitrogen-vacancy centers,Biot-Savart law,Ampère's law,magnetic field imaging,current density
更新于2025-09-19 17:15:36
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Quantum reference beacon–guided superresolution optical focusing in complex media
摘要： Optical scattering is generally considered to be a nuisance of microscopy that limits imaging depth and spatial resolution. Wavefront shaping techniques enable optical imaging at unprecedented depth, but attaining superresolution within complex media remains a challenge. We used a quantum reference beacon (QRB), consisting of solid-state quantum emitters with spin-dependent fluorescence, to provide subwavelength guidestar feedback for wavefront shaping to achieve a superresolution optical focus. We implemented the QRB-guided imaging with nitrogen-vacancy centers in diamond nanocrystals, which enable optical focusing with a subdiffraction resolution below 186 nanometers (less than half the wavelength). QRB-assisted wavefront-shaping should find use in a range of applications, including deep-tissue quantum enhanced sensing and individual optical excitation of magnetically coupled spin ensembles for applications in quantum information processing.
关键词： complex media,nitrogen-vacancy centers,quantum imaging,superresolution,quantum reference beacon,optical focusing,wavefront shaping
更新于2025-09-19 17:15:36
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Oxygen vacancy-assistant enhancement of photoluminescence performance of Eu3+ and La3+-codoped BiOCl ultrathin nanosheets
摘要： The Eu3+ and La3+ co-doped BiOCl ultrathin nanosheets were prepared through a facile solvothermal method. The samples were characterized using different techniques to study the structure, morphology, and luminescence. The solvothermal derived samples exhibit the morphology of ultrathin nanosheet. The photoluminescence spectrum of the Eu3+ ions doped BiOCl sample shows a broad emission band in the wavelength range of 380–480 nm due to the oxygen vacancies present in the sample. The spectrum also shows sharp characteristic emission peaks of Eu3+ ions. The intensity of this broad emission band increases with the incorporation of La3+ ions, due to the increase in oxygen vacancies. These results were demonstrated by the XPS spectra for all the samples. It was found that the overall luminescence intensity for the BiOCl: Eu3+, La3+ ultrathin nanosheet was about 300% stronger than the BiOCl: Eu3+ ultrathin nanosheet. As the La3+ ions concentration increases the CIE values shift from bluish-white region to white.
关键词： Oxygen vacancy,Solvothermal,Photoluminescence,BiOCl,Ultrathin nanosheet
更新于2025-09-19 17:15:36
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Evaluation of the relationship between the magnetism and the optical properties in SrTiO3-δ defective systems: Experimental and theoretical studies
摘要： To explore the relationship between optical properties, oxygen vacancies and magnetism in SrTiO3, we prepared a series of SrTiO3-δ (δ=0.00, 0.125 and 0.250) samples by solid state reaction method followed by the creation of oxygen vacancies-δ. Surface composition and chemical valence state in the synthesized compounds were examined by X-ray photoelectron spectroscopy (XPS). The Fourier Transform Infrared spectroscopy (FT-IR) spectra showed that the transmission properties change with oxygen vacancies introduction. Ultraviolet-visible absorption revealed that optical properties were highly dependent on oxygen vacancies concentrations. When the magnetic field was applied, magnetization showed weak-ferromagnetism at room temperature on SrTiO3-δ non-sto?chiometric systems. Yet, it was reversed showing diamagnetism on SrTiO3 perfect crystal. The large concentration of oxygen vacancies (δ=0.250) reduced ferromagnetism and optical absorption, implying the possible presence of a relationship between the magnetism and the optical properties. Theoretical results showed two types of electronic contributions to magnetism, one of which emanates from localized states below the conduction band minimum, and the other comes from itinerant electrons of Ti atoms lying further away from the oxygen-vacancy. The electronic structures and magnetic properties were calculated by Full-Potential Linear Augmented Plane Wave (FP-LAPW) method within the Generalized Gradient Approximation (GGA) and the atomic relaxations introduced by the oxygen vacancies host in a fully self-consistent way. The results shed some light on the promising magneto-optical properties of the SrTiO3-δ materials.
关键词： Density Functional Theory (DFT),Optical properties,Oxygen vacancy,SrTiO3,Magnetism
更新于2025-09-19 17:15:36
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P-functionalized and O-de???cient TiOn/VOm nanoparticles grown on Ni foam as electrode for supercapacitor: epitaxial grown heterojunction and visible-light-driven photoresponse
摘要： P-TiOn-VOm nanowires were grown on nickel foam (NF) by one-pot hydrothermal and further vapor deposition/phosphorization method. It is found low valence states of titanium oxide and deficient-oxygen coexist in P-TiOn-VOm/NF. Furthermore, (TiO1.25)3.07 (denoted as TiOn) and VO (denoted as VOm) possess similar structures and matched facets, their epitaxial growth leads to the formation of TiOn/VOm heterostructure with a formation energy of -1.59 eV. P-TiOn-VOm/NF possesses good electron conductivity, and electrons can be transferred from Ti to V centers, as evidenced by DFT calculations and XPS spectra. As a result, the specific capacity of P-TiOn-VOm/NF can reach 785 C g-1 at 1 A g-1 in the potential range of 0~ 0.55 V vs Hg/HgO, which is much larger than those of VOm/NF, P-VOm/NF and P-TiO2-VOm/NF. On the other hand, the TiOn/VOm heterostructure also favors for the separation and transfer of photoinduced electrons and holes, and P-TiOn-VOm/NF exhibits visible-light-driven photoresponse. Under the visible light illumination, the specific capacity of P-TiOn-VOm/NF is increased 6.2 % relative to that in dark. Furthermore, the P-TiOn-VOm/NF//activated carbon (/ AC) asymmetric supercapacitor (ASC) shows an energy density of 37.2 Wh kg-1 at power density of 1 kW kg-1, and excellent cycling performance with 93.6 % capacity retention after 10000 cycles at 5 A g?1, which is comparable to and even superior to those of titanium oxides and vanadium oxides. It is proposed a promising achievement to improve the energy storage performance of P-TiOn-VOm through the P-functionalization and O-deficiency in this work.
关键词： Phosphorus functionalized,Oxygen vacancy,TiOn-VOm,Supercapacitors
更新于2025-09-19 17:13:59
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Boosting Photovoltaic Performance and Stability of Super-halogen Substituted Perovskites Solar Cells by Simultaneous Methylammonium Immobilization and Vacancy Compensation
摘要： Perovskite solar cells (PSCs) are susceptible to intrinsic structural instability associated with the presence of inorganic halide anions and organic cations vacancies, thus leading to the deterioration or even premature failure of devices. Herein, we develop an efficient strategy using super-halogen BH4- substitution to simultaneously immobilize methylammonium and substitute iodide vacancy for high performance PSCs based on the di-hydrogen bonding interactions. The introduced super-halogen BH4- groups not only significantly reduce the vacancies density but also effectively inhibit the decomposition of CH3NH3+ group by forming perovskite CH3NH3PbI3-x(BH4-)x. The power conversion efficiency (PCE) of the assembled mesoporous devices is remarkably promoted from 18.43% to 21.10%, accompanied by significant increase of both Jsc and Voc without obvious hysteresis. The superior PSCs can retain 90% and 80% of their initial PCE even after being stored for 1200 hours under environmental conditions (50 ± 10% RH) and 240 hours at 85 °C in dark, respectively. Moreover, it delivers excellent optical stability under ultraviolet illumination. This work provides an avenue to improve both the long-term stability and photovoltaic performance of PSCs.
关键词： stability,vacancy substitution,perovskite solar cells,super-halogen BH4-,methylammonium immobilization
更新于2025-09-19 17:13:59
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: Why Sn substitution should be preferred to Pb vacancy for optimum solar cell efficiency
摘要： Methylammonium lead halide (MAPbI3) perovskite has emerged as one of the frontier optoelectronic semiconductors. To avoid lead toxicity, the role of Sn substitution and Pb vacancy (Pb-(cid:2)) are addressed in regulating stability and solar cell ef?ciency of MAPb1?X ?Y SnX (cid:2)Y I3 perovskite using hybrid density functional theory (DFT). The role of spin-orbit coupling (SOC) and the electron’s self-interaction error are examined carefully. We ?nd to reduce the Pb content from pristine MAPbI3, Sn substitution has a more favorable thermodynamic stability than creating Pb-(cid:2). Moreover, on substituting Sn, due to strong s-p and p-p couplings, the lower parts of the conduction band gets shifted downwards, which results in the reduction of the band gap (direct). This further helps us to get a high optical absorption coef?cient (redshifted) and maximum solar cell ef?ciency in MAPb1?X SnX I3 for 0 < X (cid:2) 0.5.
关键词： spin-orbit coupling,MAPbI3,solar cell efficiency,Pb vacancy,thermodynamic stability,Sn substitution,Methylammonium lead halide,hybrid density functional theory,optical absorption coefficient
更新于2025-09-19 17:13:59