Electrically driven optical emission from the negatively charged nitrogen-vacancy (NV-) centers is essential for the realization of diamond-based quantum devices. Attempts have been made to achieve electrical excitation using complex device structures and electric fields, but no clear success has been achieved. The zero-phonon line (ZPL) of NV-centers is rarely observed under electrical excitation. The absence of NV-ZPL under electrical excitation may be attributed to an increased ionization rate of the NV-centers due to high-energy electron/hole injection. To realize electrically driven NV-centers, it is crucial to understand and control the luminescence mechanism of NV-centers under high-energy electron/hole injection. Cathodoluminescence (CL) based on electron beam excitation can generate numerous electron-hole pairs, enabling rapid evaluation of NV-centers without requiring electric fields and device structures. In this study, we investigated the luminescence properties of NV-centers by investigating intrinsic materials factors (substitutional nitrogen concentration, negative and neutral NV centers concentrations) and extrinsic measurement conditions (temperature, excitation power, etc.) using the CL method.

表面化学在电化学、多相催化等领域具有重要应用价值.由Hammer和Nørskov教授提出的D带中心理论作为该领域的代表性成果,早期被广泛用于预测吸附强度.该理论认为,材料的D带中心值(εd)能级越低,其吸附能力越弱.然而,随着研究的深入,该理论在预测精度方面逐渐显现出局限性,特别是在解释小颗粒金属体系和复杂多金属体系的吸附行为时,出现了反常现象.此外,该理论未充分考虑吸附位点和吸附质特性等因素,而实际上,表面活性位点的差异和吸附质自旋多重态都会显著影响吸附能.尽管2013年Nørskov教授团队通过引入D带宽度Wd对理论进行了改进,但预测效果仍不理想.2018年,随着Lobster软件的开发,晶体轨道哈密顿布居(COHP)理论得到广泛应用,但其精度仍有待提高,且积分COHP(ICOHP)描述符的物理意义尚不明确.因此,亟待寻求新的、更为完善的理论来描述表面吸附强度. 针对这一问题,北京化工大学曹达鹏团队近期提出了一种新的成键与反键轨道稳定电子布居差理论(BASED),该理论不仅可以成功地解释D带中心理论的异常现象,在预测活性位点上中间体的吸附能和键长时,也表现出更高的准确性.同时,基于BASED理论,观察到吸附过程中自旋过渡态的一种新现象:当活性中心原子与中间体的距离接近2.5 Å时,系统通常会形成不稳定的高自旋过渡态,而这种状态能够显著增强活性中心对中间体的吸附能力. 综上所述,该论文系统阐释了D带中心理论存在的反常现象,并创新性地提出BASED理论用于评估表面吸附强度.研究发现,D带中心理论出现反常现象的根本原因在于:其仅考虑了轨道能级位置(εd),却忽略了成键电子数的影响,且未充分考虑吸附后费米能级处需形成成键轨道这一关键因素.相比之下,BASED理论在吸附能和键长预测方面展现出更高的精度,不仅为开发新一代量化计算软件的开发奠定了重要理论基础,更为深入理解表面催化过程提供了全新的物理视角.这一理论突破对表面化学研究具有重要指导意义.

The emergence of global phase coherence due to the proximity effect in heterogeneous and disordered superconductor systems has been an issue of long-standing interest. Recently, we have reported that a highly disordered fractal MgO/MgB2 nanocomposite exhibits bulk-like superconducting properties with isotropic pinning, showing an excellent phase-coherent capability irrespective of the low volume fraction (similar to 30 vol. %) of MgB2 [Uchino et al., Phys. Rev. B 101, 035146 (2020); Teramachi et al., Phys. Rev. B 108, 155146 (2023)]. In this work, we show from 3D focused ion beam scanning electron microscopy data that in the nanocomposite, a complex MgO/MgB2 microstructure spreads isotropically throughout the sample with a constant fractal dimension of similar to 1.67. Atomic-resolution scanning transmission electron microscopy has revealed that the interfaces are atomically clean and free from amorphous grain boundaries. Detailed ac susceptibility measurements have demonstrated a smooth crossover from an intragranular to an intergranular superconducting regime. Also, spatially resolved cathodoluminescence measurements have demonstrated that oxygen vacancies in the MgO-rich phase tend to aggregate near the MgO/MgB2 boundary regions, forming long channels of oxygen vacancies through the nanocomposite. These channels of oxygen vacancies are likely to be responsible for the long-range carrier transfer and the related proximity effect via the coherent tunneling of charge carriers among the oxygen vacancy sites. Our results imply that the fractal-like MgO/MgB2 microstructure with atomically clean interfaces will induce the phase-coherent transport of charge carriers in the MgO-rich regions, leading to the observed long-range proximity effect and the resulting bulk-like superconductivity in this highly disordered system. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Negatively charged boron vacancy (VB-) ensembles in hexagonal boron nitride (h-BN) have attracted considerable attention as a promising platform for quantum sensing. Current challenges include the experimental validation of the spatial distribution and electronic states of optically active VB- and optically inactive neutral boron vacancy (VB0) defects. To address these issues, we employ electron energy loss spectroscopy (EELS) combined with scanning transmission electron microscopy (STEM) using monochromated 30-keV electrons, effectively reducing background interference. This approach unveils distinct spectral peaks at 2.5 and 1.9 eV, corresponding to VB- and VB0 defects, respectively. Furthermore, we achieve nanometer-scale concentration mapping for VB- and VB0 defects, advancing insights into spin defect configurations crucial for optimizing quantum sensor performance.

Negatively charged nitrogen-vacancy (NV-) centers in diamond produce a characteristic optical zero-phonon line (ZPL) at 637 nm. This emission line can be observed under optical excitation (i.e. photoluminescence), but is rarely observed under electron excitation (i.e. cathodoluminescence). This study reports that low-temperature (80 K) and low energy (5 keV) cathodoluminescence spectroscopy is able to detect emission peak or spectral dip at the ZPL of NV- centers. The spectral dip was observed in the diamond samples with high concentration of NV- centers produced by high-energy (2 MeV) e-beam (EB) irradiation. The effects of EB irradiation fluence, NV- centers concentration and substitutional nitrogen concentration on the formation of spectral dip were discussed, and a model based on the NV- absorption of NV0 emission sideband is proposed.

An area-selectable Mg doping via ion implantation (I/I) is essential to realize gallium nitride (GaN) based power switching devices. Conventional post-implantation annealing forms considerable defects in the GaN, resulting in extremely low activation efficiency. The recent invention of ultrahigh-pressure annealing (UHPA) has substantially improved the p-type activation efficiency; however, the UHPA causes an unexpected Mg diffusion. Thus, both annealing processes resulted in a much lower Mg concentration in the GaN matrix than the Mg dose. In this study, the effect of a sequential N I/I for p-type Mg-implanted GaN was investigated by the correlative cathodoluminescence, transfer length method, scanning transmission electron microscopy, and atom probe tomography (APT) analyses. APT results have revealed that the sequential N I/I can successfully maintain the Mg concentration in the GaN matrix in the higher range of 10(18) cm(-3) or more. Our investigation suggests that sequential N I/I is a promising technique to maintain the Mg concentration higher and improve the p-type activation efficiency.

White LEDs combined by blue LED chip and yellow YAG: Ce phosphor are the mainstream of the lighting industry. However, due to the lack of red light component, it is difficult to meet the requirements of warm white lighting. The novel needle-like Ba5Si11Al7N25:Eu2+ particle discovered by the single-particle-diagnosis method shows a broad yellow emission band centered at similar to 570 nm and a FWHM of 98 nm. Compared with YAG: Ce phosphor, the novel Ba5Si11Al7N25:Eu2+ phosphor exhibits longer emission wavelength, indicating potential application in warm white LEDs. In this work, the phase-pure powder of Ba5Si11Al7N25:Eu2+ is obtained in a non-stoichiometric ratio by the double-crucible method, and it shows similar luminescent properties as the single particle. Upon excitation with violet light (400 nm), the maximum emission wavelength of the as-prepared Ba5(1-x)Si11Al7N25: 5xEu(2+) phosphors shift from 558 nm to 591 nm with Eu2+ ions concentration increasing, and the full width at half-maximum (FWHM) increase from 87 nm to 100 nm. The broad emission band is attributed to three luminescent centers corresponding to three different Ba2+ ions sites Ba5Si11Al7N25:Eu2+ phosphor, which is demonstrated by time-resolved emission spectra and the decomposition of the emission spectrum at 4 K. The Ba5Si11Al7N25:Eu2+ phosphor shows a small thermal quenching with a quenching temperature as high as 700 K. The as-prepared phosphor can absorb both of UV and blue light effectively and exhibits similar quantum efficiency under the excitation of 400 nm (58.5 %) and 450 nm (54.5 %). The fabricated white LED lamp emitted a warm white light with CIE coordinates of (0.3838, 0.3252) and CCT = 3412 K, implying the potential applications in warm w-LEDs.

3C-SiC/4H-SiC heterostructures have great potential for high-electron-mobility transistors. The growth of high-quality 3C-SiC epilayers on 4H-SiC substrates can be realized by controlling step growth with proper surface pretreatment. We investigated the optical and electrical properties of extended defects in 3C-SiC by cathodoluminescence (CL) spectroscopy. CL images revealed the distribution of extended defects in 3C-SiC. The impact of surface pretreatment on the growth of high-quality 3C-SiC is discussed.

We have investigated the impact of high-temperature Mg-implantation in GaN layers on distribution of Mg-enriched defects using scanning transmission electron microscopy and atom probe tomography. For this, 1 × 1019 cm−3 Mg ions have been implanted in GaN layers at room temperature (RT) and 1000 °C, followed by annealing at 1300 °C. A smaller number of Mg-enriched defects were observed in the sample implanted at 1000 °C in comparison to the sample implanted at RT. The implantation of Mg ions at 1000 °C resulted in a higher amount of randomly distributed Mg in the GaN matrix, which, in turn, leads to more uniform and enhanced donor–acceptor pair emission, leading to higher Mg activation.

An area selective doping via ion implantation is a key technology to realize gallium nitride (GaN) based energy-efficient power devices; however, conventional annealing leads to the formation of numerous Mg-enriched defects, which result in inefficient p-type activation. The recent invention of ultra-high-pressure annealing (UHPA) has enabled a significant improvement in p-type activation efficiency. In this study, we investigated the formation of Mg-enriched defects in Mg implanted GaN followed by annealing under either conventional atmospheric pressure or ultra-high-pressure. Unlike the conventional annealing, UHPA leads to a much lower number density of Mg-enriched defects. Correlative scanning transmission electron microscopy, atom probe tomography, cathodoluminescence, and secondary ion mass spectrometry analyses have shown that the number density of Mg-enriched defects is substantially suppressed by the UHPA. The dissolved Mg concentrations in the GaN matrix for both the conventional and the UHPA samples are almost of the same value, approximately 2 × 1018 cm−3; however, the UHPA sample shows over one order of magnitude stronger intensity of donor–acceptor-pair emission than the conventional one. Thus, the implanted Mg is effectively activated as acceptors through the UHPA technique.

Perovskite bulk crystals (BCs) have been generally synthesized and grown via the temperature-mediated processes. Here, we report a facile strategy of using antisolvent droplets for assisting the crystallization and growth of large high-quality perovskite BCs (similar to 5 mm) at room temperature. The formation of either CsPbBr3 or Cs4PbBr6 BCs was controllable through tuning the composition of solvents used during growth. Such high-quality as-grown BCs were chosen for demonstrating the carrier-lattice interactions under photoexcitation operation. The wavelength-dependent time-resolved photoluminescence dynamics revealed that both the blue-side and red-side "solvation-like - effect between the photocarriers and surrounding lattices existed in the BCs, whereas only the blue-side one was obviously observed in the nanocrystals. The antisolvent droplet-assisted crystallization offers a versatile strategy of growing perovskite BCs with tunable compositions, and the distinct solvation behaviors enrich a fundamental understanding of photocarrier energy relaxations in perovskites with nanoscale and bulk forms.

The effects of reactive gas flow conditions on nonpolar AlN film growth on MnS/Si (100) substrates using reactive DC magnetron sputtering were investigated. During AlN deposition at a substrate temperature of 750 °C, the MnS surface can be unintentionally nitrided, resulting in a decrease in the crystallinity of the AlN. Low-temperature growth of the AlN layer at 300 °C prevents this nitridation and results in the crystallization of nonpolar AlN. A N 2 flow equal to 30% of the Ar sputtering gas flow was found to improve the crystallinity of the nonpolar AlN and to reduce nitrogen defects, which play an important role in interfacial reactions. Nitrogen defects promote the formation of alloys such as AlMn and MnSi that degrade the interface and can significantly decompose the MnS. A higher proportion of N 2 improves the nonpolar AlN crystallinity, reduces the concentration of defects and suppresses reactions at the AlN/MnS interface.

Crystalline silicon solar cells are developing towards higher conversion efficiency, however, the surface recombination and Auger recombination from heavily doped silicon are the main limit. Some metal oxides are of great interest because of their selective contact performance with crystalline silicon, which can minimize the carrier recombination in the contact area. Especially, due to the high work function of molybdenum oxide (MoOx), the MoOx film can provide excellent hole transport and electron blocking properties for the silicon surface. Here, we have deposited MoOx films on the surface of silicon wafer by spin-coating a copper hydromolybdate solution. The MoOx film can provide superior passivation quality compared to thermal evaporated one, with the tau eff of 110.6 mu s (Delta n = 1015 cm-3) obtained on n-type Czochralski silicon. Moreover, the passivation of MoOx film can be further improved by annealing at low temperature and under reduced atmosphere environment. The dense surface morphology of amorphous films and formation of Si-O-Si bonds by annealing are the main reasons for improved silicon surface passivation. This work demonstrates the feasibility of using solutionprocessed transition metal oxides as effective and low-cost carrier-selective passivating contacts for silicon photovoltaic devices.

A novel method of preparing ultrathin aluminum oxide films by rapid thermal annealing (RTA) treatment for effective silicon surface passivation is proposed. The high‐temperature RTA processing (750–825 °C) for tens of seconds in an oxygen atmosphere completely converts the thermally evaporated aluminum metal nanofilms (1–5 nm) on crystalline silicon to aluminum oxide (Al2O3) films, with a thin SiOx layer formed at the interface between the silicon and the Al2O3. The generated Al2O3 film can provide superior passivation quality for the silicon surface, even better than that obtained by the thermal atomic layer deposition technique. Moreover, the growth kinetics of the Al2O3 passivating film indicates that it is a diffusion‐controlled activation process, with an energy barrier of 3.3 eV for aluminum ions diffusing across the metal/oxide interface.

The extended defects in m‐plane seed‐grown GaN substrate have been investigated by cathodoluminescence (CL) and transmission electron microscopy (TEM). The presence of basal‐plane stacking faults (BSFs) has been confirmed in the edge part of seed growth. The luminescence features of BSFs are characterized by high‐resolution CL with monochromatic image and spatially resolved spectral analysis. Most stacking faults are intrinsic I1 BSFs with characteristic emission peak centered at 3.42 eV. There are a few intrinsic I2 BSFs which show varied emission energies of 3.33–3.38 eV. The motion of dislocations under electron beam irradiation has also been monitored and the correlation with stacking faults is discussed.

Atomic metal wires have great promise for practical applications in devices due to their unique electronic properties. Unfortunately, such atomic wires are extremely unstable. Here we fabricate stable atomic silver wires (ASWs) with appreciably unoccupied states inside the parallel tunnels of α-MnO 2 nanorods. These unoccupied Ag 4 d orbitals strengthen the Ag–Ag bonds, greatly enhancing the stability of ASWs while the presence of delocalized 5 s electrons makes the ASWs conducting. These stable ASWs form a coherently oriented three-dimensional wire array of over 10 nm in width and up to 1 μm in length allowing us to connect it to nano-electrodes. Current-voltage characteristics of ASWs show a temperature-dependent insulator-to-metal transition, suggesting that the atomic wires could be used as thermal electrical devices.

Group-IV alloy semiconductors have garnered increasing attention as advanced thin-film materials for next-generation electronics. We have demonstrated polycrystalline Ge thin films with the highest recorded crystallinity and carrier mobility using a multistep heating process in solid-phase crystallization. In this study, we apply these recent findings in Ge to Si1-xGex (x: 0-1) and Ge1-ySny (y: 0-0.04) alloys and investigate their crystal and electrical properties. For all compositions, controlling the temperature in each stage increases the grain size to the micrometer order, improving the carrier mobility and reducing the number of defect-induced acceptors. Sb doping further enlarges the grain size (up to 10 mu m) in addition to n-type conduction control, whereas the electron concentration varies with the composition. Both hole and electron mobilities significantly depend on the composition owing to the effects of carrier effective mass, grain size, and carrier concentration: the hole and electron mobilities peak at 350 and 150 cm(2) V(-1)s(-1), respectively. The relationship between the composition and various physical properties revealed in this study will contribute to the better understanding, control, and device application of polycrystalline thin films based on group-IV alloy semiconductors. (C) 2021 Elsevier B.V. All rights reserved.

The precise control of p-GaN is a crucial issue for developing GaN-based power devices. Mg as an acceptor is commonly used in p-type doping; however, the Mg diffusion through threading dislocations (TDs) has not been well addressed. To clarify the Mg diffusion and activation along TDs, we have performed a systematic characterization of a Mg-implanted homoepitaxial GaN layer grown on a freestanding substrate. Active-Mg related donor–acceptor pair (DAP) emission from certain TDs is identified by cathodoluminescence (CL). Dislocations with and without DAP emission are investigated structurally and compositionally based on etch pits, transmission electron microscopy, and atom-probe tomography. Direct evidence of Mg distribution around edge- and mixed-type TDs is obtained. There exists a significant difference in the Mg concentration and incorporation states between different types of TDs.

Electron-beam-induced current (EBIC) and cathodoluminescence (CL) have been applied to investigate the electrical and optical behaviors of dislocations in SrTiO3. The electrical recombination activity and defect energy levels of dislocations have been deduced from the temperature-dependent EBIC measurement. Dislocations contributed to resistive switching were clarified by bias-dependent EBIC. The distribution of oxygen vacancies around dislocations has been obtained by CL mapping. The correlation between switching, dislocation and oxygen vacancies was discussed.

NIMS , Tohoku Univ. Univ. of Tsukuba Jun Chen, Wei Yi, Peng Wang, Shun Ito, and Takashi Sekiguchi 3 E-mail: CHEN.Jun@nims.go.jp Oxygen vacancies behave as n-type dopants in SrTiO3. Previous studies have addressed the correlation between oxygen vacancies and electrical conductivity. The conductivity could be strongly varied when SrTiO3 is exposed to vacuum or O2 ambient. One the other hand, the extended defects (grain boundaries, dislocations, etc.) in SrTiO3 may also affect the distribution of oxygen vacancies. In this study, the impact of dislocations on oxygen vacancies in un-doped SrTiO3 single crystal has been investigated by cathodoluminescence (CL). The dominated luminescence peak located at ~ 2.8 eV is originated from oxygen vacancies. Enhanced luminescence has been observed at specific dislocations with the accumulation of oxygen vacancies as shown in Fig. 1. Under annealing either in oxidizing or reducing atmosphere, the diffusivity of oxygen ions at dislocation cores is nearly the same as that in the bulk [1]. CL results suggest that the accumulation of oxygen vacancies is easily triggered by certain dislocations. However, there is no significantly enhanced diffusion of oxygen vacancies along dislocations. This work may also provide a feasible way to modulate the oxygen vacancy content in oxide semiconductors.