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Visualizing Phase Segregation in Mixed-Halide Perovskite Single Crystals
摘要： Mixed organolead halide perovskites (MOHPs), CH3NH3Pb(BrxI1?x)3, have been shown to undergo phase segregation into I-rich domains under illumination, presenting a major challenge to their development in photovoltaic and light-emitting devices. Recent work suggests phase segregated domains are localized at crystal boundaries, driving investigations into the role of edge structure and the growth of larger crystals with reduced surface area. Herein, a method for growing large (30×30×1 μm) monocrystalline MAPb(BrxI1?x)3 single crystals is presented. The direct visualization of the growth of nanocluster-like I-rich domains throughout the entire crystal revealed grain boundaries are not required for this transformation. Narrowband fluorescence imaging and time-resolved spectroscopy provided new insight into the nature of phase segregated domains and the collective impact on optoelectronic properties.
关键词： perovskite,photoluminescence,lifetime,phase segregation,single crystal
更新于2025-09-09 09:28:46
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The luminescent properties comparison of RE2O3:Eu(RE=Lu,Y,Sc) with high and low Eu doping concentrations
摘要： Single crystal scintillators of RE2O3:Eu(RE=Lu, Y, Sc) with high (8%) and low (1%) Eu doping concentration were grown by the optical floating zone method. The luminescence and scintillation properties have been investigated and compared thoroughly. Correlated measurements of afterglow curves, photoluminescence excitation and photoluminescence, photoluminescence decay curves and X-ray excitation curves were performed. Lu2O3:Eu and Y2O3:Eu present significant afterglow intensity decreasing after high Eu concentration doping. While for the Sc2O3:Eu, its afterglow intensity even increases slightly. The luminescence efficiencies of high doping concentration samples are weaker than that of the low concentration ones due to the concentration quenching. The integrated X-ray excitation luminescence reveals the scintillation luminescence efficiencies of samples with the high concentration or the low one both have the following sequence:Lu2O3:Eu＞Y2O3:Eu＞Sc2O3:Eu.
关键词： europium-doped sesquioxide,floating zone method,scintillation properties,afterglow,single crystal
更新于2025-09-09 09:28:46
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Investigation of Single-Crystal Niobium for Microwave Kinetic Inductance Detectors
摘要： The Advanced Technology Centre (ATC) of National Astronomical Observatory of Japan is developing microwave kinetic inductance detectors (MKIDs) for large-array pixel cameras for millimeter and sub-millimeter astronomy. We investigated single-crystal Nb thin layers to form superconducting microresonators. We compared the performances of MKIDs based on crystalline Nb structure and those based on poly-crystalline Nb. We carried out the entire manufacture of the detectors in the ATC clean room. DC magnetron sputtering is used to grow single-crystal Nb films on r-plane sapphire substrates at an elevated temperature of 800 °C. The residual resistivity ratio (RRR) measured on these single-crystal Nb layers reached values ranging from 40 to 80. We made MKIDs with this crystalline Nb layer, and we measured internal quality factors of the detectors up to 106. The measurement of the noise power spectral density of these MKIDs gave a low value of ? 95 dBc/Hz from 100 Hz to 100 kHz. The internal quality factor Qi and the fractional resonance frequency change δf r/f r of MKIDs with respect to the temperature variation are usually following the extended Mattis–Bardeen equations. However, we noticed a deviation from the theoretical prediction for temperature lower than 1 K (in our case). This deviation has already been observed on Al MKIDs and explained by a theory taking into account the Kondo effect and the kinetic inductance contribution. We demonstrated that our measurements on single-crystal Nb MKIDs are also in agreement with the same theory.
关键词： Microwave kinetic inductance detector,Single-crystal niobium,Superconducting thin films
更新于2025-09-09 09:28:46
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Influence of the Iodide to Bromide Ratio on Crystallographic and Optoelectronic Properties of Rubidium Antimony Halide Perovskites
摘要： Rubidium antimony halides are a promising low toxic alternative to organo-lead halide perovskites as photovoltaic material. In this contribution we systematically investigate the influence of varying the bromide to iodide ratio on the structural, optical and photovoltaic properties of Rb3Sb2Br9-xIx (x = 0 – 9). Single crystal data reveal that all compounds crystallize in a 2D-layered monoclinic crystal structure. Sequential substitution of iodide with the smaller bromide does not change the crystal system, however, increasing the bromide content results in a shrinkage of the unit cell as well as in a blue shift of the absorption onset, increasing the band gap from 2.02 eV to 2.46 eV. Whereas the photovoltaic properties of bromide rich compounds are limited due to a preferential orientation of the layered structure parallel to the substrate, which is detrimental to charge transport, solar cells with Rb3Sb2I9 as absorber material display power conversion efficiencies of 1.37%. Moreover, the devices exhibit low hysteresis properties and are stable for more than 150 days stored under inert atmosphere.
关键词： single crystal,thin film,antimony perovskites,photoluminescence,lead-free perovskite,solar cells,structural characterization
更新于2025-09-09 09:28:46
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Molecular properties, crystal structure, Hirshfeld surface analysis and computational calculations of a new third order NLO organic crystal, 2-aminopyridinium benzilate
摘要： A third order nonlinear optically active (NLO) organic proton transfer compound was synthesized by the reaction between 2-aminopyridine and benzilic acid. Single crystals of the product, 2-aminopyridinium benzilate, (2-APB) were grown by slow evaporation technique and the structure of 2-APB was confirmed by single crystal X-ray diffraction. In the structural network, cations and anions are linked through N+-H…O- intermolecular hydrogen bonding interactions. Elemental analysis, thermal analysis, UV-Vis, FT-IR and 1H and 13C NMR spectroscopic analyses were carried out to assess the structure and chemical makeup of the 2-APB crystal. Computational studies that include optimization of molecular geometry, natural bond orbital (NBO), Mulliken atomic charge and HOMO-LUMO analyses were also performed using B3LYP method at 6-311+ G (d,p) level of theory to explore various intermolecular interactions especially hydrogen bonding. Hirshfeld surface analysis indicates that the contacts involving hydrogen such as H…H, C…H and O…H have greater influence on the molecular properties of 2-APB.
关键词： NBO analysis,Hydrogen bonding,DFT,Single crystal XRD,Hirshfeld surface analysis
更新于2025-09-04 15:30:14
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25 nm Single-Crystal Silicon Nanowires Fabricated by Anisotropic Wet Etching
摘要： We report a top-down method for fabricating ultra-high aspect ratio single-crystal silicon nanowires. The fabrication method is based on the standard photolithography technique and anisotropic wet etching of the single-crystal silicon in KOH solution. SiO2 mask nanolines used for patterning single-crystal silicon nanowires are formed by the undercut etching of thin SiO2 layer in buffered hydrofluoric solution. The minimum width of the SiO2 mask nanolines are 50 nm. The length of SiO2 mask nanolines is 2 cm. The single-crystal silicon nanowires have been successfully transferred from the SiO2 mask nanolines by KOH anisotropic wet-chemical etching. The minimum width of the silicon nanowire has obtained to be 25 nm. The fabricated single-crystal silicon nanowires have trapezoidal and triangular cross sections, which are useful for applications in nanoelectronic and nanophotonic elements.
关键词： All Wet Chemical Etching,Wafer-Scale Fabrication,Single-Crystal Silicon Nanowire,Photolithography
更新于2025-09-04 15:30:14
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Temperature Driven Phase Transition of Organic-Inorganic Halide Perovskite Single Crystals
摘要： Organic-inorganic halide perovskite single crystals undergo phase transition of being cubic, tetragonal, or orthorhombic depending on the temperature. We investigated the CH3NH3PbBr3?xIx single crystals grown by the inverse temperature crystallization method with temperature-dependent UV-Vis absorption and photoluminescence. From the temperature-dependent absorption measurement, the optical band gap is extracted by derivation of absorption spectrum fitting and Tauc plot. In our results, CH3NH3PbBr3?xIx single crystals show that an abrupt change in optical band gap, PL peak position and intensity appears around 120 K - 170 K regions, indicating the phase transition temperature.
关键词： Photoluminescence,Phase transition,Perovskite single crystal,Temperature-dependent absorption,Derivation of absorption spectrum fitting (DASF)
更新于2025-09-04 15:30:14
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High-Quality Cuboid CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> Single Crystals for High Performance X-Ray and Photon Detectors
摘要： Organic–inorganic halide hybrid perovskite materials are promising materials for X-ray and photon detection due to their superior optoelectronic properties. Single-crystal (SGC) perovskites have increasingly attracted attention due to their substantially low crystal defects, which contribute to improving the figures of merit of the devices. Cuboid CH3NH3PbI3 SGC with the naturally favorable geometry for device fabrication is rarely reported in X-ray and photon detection application. The concept of seed dissolution-regrowth to improve crystal quality of cuboid CH3NH3PbI3 SGC is proposed and a fundamental understanding of the nucleation and growth is provided thermodynamically. The X-ray detector fabricated from cuboid CH3NH3PbI3 SGC demonstrates the firstly reported high sensitivity of 968.9 μC?1 Gy?1 cm?2 under ?1 V bias. The results also show that the favorable crystal orientation and high quality of cuboid CH3NH3PbI3 leads to better responsivity and faster response speed than the more common dodecahedral CH3NH3PbI3 in photodetection. Consequently, the work paves a way to synthesize high-quality perovskite SGCs and benefits the application of MAPbI3 SGCs with preferred crystal orientation and favorable crystal geometry for emerging device applications.
关键词： photodetector,cuboid,single crystal,perovskite,X-ray detector
更新于2025-09-04 15:30:14
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Single-crystal investigation of the proposed type-II Weyl semimetal CeAlGe
摘要： We present details of materials synthesis, crystal structure, and anisotropic magnetic properties of single crystals of CeAlGe, a proposed type-II Weyl semimetal. Single-crystal x-ray diffraction con?rms that CeAlGe forms in a noncentrosymmetric I 41md space group, in line with predictions of nontrivial topology. Magnetization, speci?c heat, and electrical transport measurements were used to con?rm antiferromagnetic order below 5 K, with an estimated magnon excitation gap of (cid:2) = 9.11 K from heat capacity and hole-like carrier density of 1.4 × 1020 cm?3 from Hall effect measurements. The easy magnetic axis is along the [100] crystallographic direction, indicating that the moment lies in the tetragonal ab plane below 7 K. A spin-?op transition to less than 1 μB /Ce is observed to occur below 30 kOe at 1.8 K in the M (H ) (H(cid:2)a) data. Small magnetic ?elds of 3 and 30 kOe are suf?cient to suppress magnetic order when applied along the a and c axes, respectively, resulting in a complex T –H phase diagram for H(cid:2)a and a simpler one for H(cid:2)c.
关键词： Weyl semimetal,CeAlGe,electrical transport measurements,single-crystal x-ray diffraction,antiferromagnetic order,magnetization,specific heat
更新于2025-09-04 15:30:14