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The Nature of the Oxygen Vacancy in Amorphous Oxide Semiconductors: Shallow Versus Deep
摘要： Using first-principles calculation, we investigate the nature of oxygen vacancy (VO), namely shallow versus deep, in the amorphous oxide semiconductor InGaZnO4 (a-IGZO), which has not been fully clarified despite its technological importance. Oxygen-deficient amorphous models are generated through the hybrid functional molecular dynamics (MD) simulations that allow for finding stable VO configurations while minimizing computational approximations. From eight independent models, we consistently find that VO serves as the shallow donor, increasing the Fermi level above the conduction band minimum. For comparison purpose, we also generate deep VO models by charging the system during MD simulations. It is found that deep VO is higher in the formation energy than shallow VO, confirming that shallow VO is the preferred type of oxygen vacancies in a-IGZO.
关键词： hybrid functional,computational physics,InGaZnO4,oxygen vacancy,density functional theory
更新于2025-09-09 09:28:46
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Direct writing of single germanium vacancy center arrays in diamond
摘要： Single photon emitters in solid-state systems with superior optical properties are of fundamental importance for they are building block candidates of many quantum optics applications. The ideal qubit will have a bright narrow band emission (i.e. high Debye Waller (DW) factor) and an access to optically read out and manipulate its spin states. Numerous candidates have been studied in diamond including the nitrogen vacancy (NV) center and more recently the silicon vacancy (SiV) center. The advantage of the SiV is its high DW factor, with nearly 80% of its emission is within its zero phonon line (ZPL). But its coherence time is limited by the narrow ground state splitting (~40 GHz) which favors single-phonon absorption from the lower branch to the upper one. This necessitates the search for an alternative system with a larger ground state splitting to suppress the phonon-mediated processes. Color centers in diamond are promising solid-state qubits for scalable quantum photonics applications. Amongst many defects, those with inversion symmetry are of an interest due to their promising optical properties. In this work, we demonstrate a maskless implantation of an array of bright, single germanium-vacancy (GeV) centers in diamond. Employing the direct focused ion beam technique, single GeV emitters are engineered with the spatial accuracy of tens of nanometers. The single GeV creation ratio reaches as high as 53% with the dose of 200 Ge+ ions per spot. The presented fabrication method is promising for future nanofabrication of integrated photonic structures with GeV emitters as a leading platform for spin-spin interactions.
关键词： diamond,germanium-vacancy centers,single photon emitters,quantum photonics,focused ion beam
更新于2025-09-09 09:28:46
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Oxygen Vacancy-Rich Ultrathin Sulfur-Doped Bismuth Oxybromide Nanosheet as a Highly Efficient Visible-Light Responsive Photocatalyst for Environmental Remediation
摘要： Designing ultrathin two-dimensional (2D) defective materials and metal-free doped materials as photocatalysts both have received enormous attentions in the field of environmental remediation due to their great potential for removing colorless contaminants. However, whether the synergism of defects and metal-free doping exists and the corresponding oxidative mechanism is unclear, which retard further developments of high performance catalysts. Here, a novel oxygen vacancy (OV)-rich ultrathin sulfur-doped BiOBr nanosheet (BB-xS) was synthesized through a facile one-step solvothermal method. Under visible light irradiation, the optimal BB-5S sample exhibited 98% degradation efficiency of 4-chlorophenol (4-CP) within 120min, which was 4.9 and 18.0 times greater than that of pristine ultrathin BiOBr and oxygen vacancy-poor sulfur-doped BiOBr, respectively. Also, this excellent photoactivity could extend to other colorless organic contaminants, such as bisphenol analogues and sulfonamides, verifying the universal applicability of BB-xS. Based on experimental results and density functional theory (DFT) calculations, it was manifested that a sub-band was generated via the synergistic effect of oxygen vacancies and sulfur doping, and it greatly enhanced the visible-light absorption capability and suppressed the photoinduced charge recombination, which would be beneficial to improve the photocatalytic activity. Additionally, the corresponding photocatalytic degradation pathway of 4-CP was also proposed. This work can provide a new protocol for the design and construction of highly active photocatalysts toward environmental remediation.
关键词： photocatalytic degradation,Ultrathin two-dimensional nanosheets,sulfur-doped,oxygen vacancy,colorless organic contaminants
更新于2025-09-09 09:28:46
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Quantum behavior of hydrogen-vacancy complexes in diamond
摘要： Hydrogen plays an essential role in the growth process of artificial diamond and can easily form complexes with lattice vacancies. Despite substantial efforts to resolve the electronic structure and the ground-state properties of the hydrogen-vacancy (HV) center, the final remarks are ambiguous, while the complexes of vacancy with two and more hydrogen atoms remain unexplored. In this paper, we used spin-polarized, hybrid density-functional theory method to investigate electronic structure and magneto-optical properties of various hydrogen-vacancy clusters in diamond. Our theoretical results indicate a very strong tendency toward the formation of HnV complexes up to four hydrogen atoms that are mostly electrically and optically active centers. One of the investigated defects introduce highly correlated electronic states that pose a challenge for density-functional theory and, therefore, require special treatment when charge- and spin-density-related properties are determined. We introduced an extended Hubbard model Hamiltonian with fully ab initio provided parameters to analyze the complex electronic structure of highly correlated H2V0 defects. The role of quantum tunneling of hydrogen in HV center and its impact on the hyperfine structure was discussed. We demonstrate that experimentally observed HV1? center is similar to well-known NV1?, i.e., I) it possesses triplet 3A ground state and 3E excited state in C3v symmetry; II) the calculated zero-phonon line is 1.71 eV (1.945 eV for NV1?). A detailed experimental reinvestigation based on optically detected electron paramagnetic resonance spectroscopy is suggested to verify whether the HV1? center has metastable singlet shelving states between the ground and excited state triplets and, as a result, whether it may exhibit a spin-selective decay to the ground state.
关键词： quantum tunneling,diamond,hydrogen-vacancy complexes,magneto-optical properties,density-functional theory,quantum behavior
更新于2025-09-09 09:28:46
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Synthesis of Self-Gravity Settling Faceted-Anatase TiO2 with Dominant {010} Facets for the Photocatalytic Degradation of Acetaminophen and Study of the Type of Generated Oxygen Vacancy in Faceted-TiO2
摘要： In this study, faceted TiO2, predominately exposed with {010} facets (T-{010}), was synthesized with a two-step hydrothermal reaction and used for the degradation of acetaminophen (ACE) in an aqueous solution. T-{010} showed considerable photocatalytic reactivity, and its easy-settling (gravity-settling, ~97% of T-{010} settled after 30 min) property demonstrated acceptable reusability. A solid-state chemical reduction approach (NaBH4) at a mild temperature (300 ?C) was used for generation of an oxygen vacancy in T-{010} and P25 (commercial TiO2). The oxygen vacancy concentrations of the samples were investigated by electron paramagnetic resonance (EPR). It was also found that NaBH4 reduction induced the generation of both surface and subsurface Ti3+ on colored P25, but only surface Ti3+ species were formed on colored T-{010}. The prepared colored TiO2 samples were successfully used for photocatalytic degradation of ACE in an aqueous solution under visible light illumination.
关键词： photocatalytic degradation,visible light,{010} facet,oxygen vacancy,settling
更新于2025-09-09 09:28:46
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One-step synthesis of hollow BaZrO3 nanocrystals with oxygen vacancies for photocatalytic hydrogen evolution from pure water
摘要： It is very challenging to synthesize perovskite oxides with controlled morphology and defect states at the same time. In this work, the BaZrO3 hollow nanostructures with oxygen vacancies were facilely synthesized through one-step solvothermal method using ethylenediamine (EDA) as solvent. The as-synthesized BaZrO3 could split pure water into H2 without addition of sacrificial agent under UV light irradiation. The photocatalytic H2 production rate is about 15 times than that of the commercial BaZrO3 (BZO-C). It is believed that the presence of oxygen vacancies and the hollow morphology made contribution to the improvement of photocatalytic performance. This work provides a reference for microstructure and defect modification of photocatalysts at the same time to enhance the photocatalytic performance.
关键词： BaZrO3,Photocatalysis,Oxygen vacancy,Pure water,Hollow structure
更新于2025-09-09 09:28:46
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Noise spectroscopy of a quantum-classical environment with a diamond qubit
摘要： Knowing a quantum system’s environment is critical for its practical use as a quantum device. Qubit sensors can reconstruct the noise spectral density of a classical bath, provided long enough coherence time. Here, we present a protocol that can unravel the characteristics of a more complex environment, comprising both unknown coherently coupled quantum systems, and a larger quantum bath that can be modeled as a classical stochastic field. We exploit the rich environment of a nitrogen-vacancy center in diamond, tuning the environment behavior with a bias magnetic field, to experimentally demonstrate our method. We show how to reconstruct the noise spectral density even when limited by relatively short coherence times, and identify the local spin environment. Importantly, we demonstrate that the reconstructed model can have predictive power, describing the spin qubit dynamics under control sequences not used for noise spectroscopy, a feature critical for building robust quantum devices. At lower bias fields, where the effects of the quantum nature of the bath are more pronounced, we find that more than a single classical noise model are needed to properly describe the spin coherence under different controls, due to the back action of the qubit onto the bath.
关键词： nitrogen-vacancy center,diamond qubit,noise spectroscopy,dynamical decoupling,quantum-classical environment
更新于2025-09-09 09:28:46
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Interaction Between Hydrogen and Vacancy Defects in Crystalline Silicon
摘要： Hydrogen is one of the most important impurities in silicon. It is a mobile and highly reactive species that can passivate dangling bonds at dislocations, surfaces, and interfaces, which has been widely used in the microelectronics and solar cell industry for improving device performance. Vacancy defects are elementary complexes containing dangling bonds, and the study of their interaction with hydrogen is of significant importance. In this work, the interactions of hydrogen with the vacancy-oxygen complex (VO) and the divacancy (V2) are discussed, which are the most dominant and fundamental vacancy defects stable at room temperature. It is shown that VO and V2 can interact with both atomic and diatomic hydrogen species. This complicates the interpretation of experimental data and results in different reaction paths in differently prepared samples. Besides, some of important electronic properties, particularly electronic levels for V2Hn with n > 1, are not experimentally established.
关键词： silicon,vacancy defects,vacancy-oxygen,hydrogen,divacancy
更新于2025-09-04 15:30:14
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Preparation and Photocatalytic Activities of Black TiO <sub/>2</sub> in Vacuum and Ambient Temperature Environment
摘要： The preparation conditions are important for the structure and properties of black TiO2. In this paper, the black rutile TiO2 with a particle size of approximately 5 nm was prepared in vacuum by the infrared nano-second laser sputtering deposition method. The study results indicated that the prepared black TiO2 exhibited high light absorption from UV to near-infrared region. The lattice distortion and Ti3+ were responsible for the upward shift in the valance band, and the oxygen vacancy states were determined to be located about 0.7–1.18 eV under the conduction band, narrowing the band gap of TiO2 from 3.2 eV to 2.1 eV. Although the black TiO2 exhibited strong adsorption effects within the full spectrum and had a higher free carrier density, the presence of excess oxygen defects resulted in a higher recombination rate of the photo electron–hole pairs, which induced a poor photocatalytic performance of the black TiO2. This work facilitates the understanding of the mechanisms mechanism of black TiO2 formation via laser ablation, and emphasized the need for the controllability and quanti?cation of oxygen vacancies.
关键词： Vacuum,Laser Ablation,Oxygen Vacancy,Photocatalytic Activity,Black TiO2
更新于2025-09-04 15:30:14
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Pulse duration effect during pulsed gate-bias stress in a-InGaZnO thin film transistors
摘要： We investigated how the zero-voltage duration (0Vd) affects the tendency of degradation during pulsed gate bias stress in a-InGaZnO thin film transistors (TFTs). DC or pulsed negative bias illumination stress (NBIS) or positive bias stress (PBS) was applied to the TFTs for effective stress time of 4,000 s. While pulsed bias stress was being applied, stress-voltage duration (SVd) was set as either 10 s or 1 s per cycle, and 0Vd was varied from 100% to 1% of the SVd. During NBIS, degradation in both threshold voltage and sub-threshold slope became increasingly severe as 0Vd was shortened. However, during pulsed PBS, these trends were almost absent. These different tendencies may occur because the cause of each stress-induced degradation is fundamentally dissimilar; NBIS involves ionization of oxygen vacancies, whereas PBS involves electron trapping. The proposed mechanism was supported by additional bias stress tests on TFTs that had been immersed in H2O, where hydrogen became dominant factor causing the degradation.
关键词： Hydrogen,IGZO,Dynamic stress,Instability,Oxygen vacancy,AC stress
更新于2025-09-04 15:30:14