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We propose and investigate a novel coherent laser array design based on laterally coupled photonic crystal surface-emitting lasers (PCSELs). As a new type of semiconductor laser technology, PCSELs have field confinement in a planar cavity and laser beam emission in the surface normal direction. By engineering lateral couplings between PCSELs with heterostructure photonic crystal designs, we can achieve coherent operations from an array of PCSELs. In this paper, we demonstrate coherent operation from a passively coupled PCSEL array design. We fabricated PCSEL array devices on a GaAs-based quantum well heterostructure at a target wavelength of 1040 nm. Experimental results show that the 2-by-2 PCSEL arrays have spectral linewidth of 0.14–0.22 nm. Beam combining performance was characterized by self-interference experiments. Similar coherency between the PCSEL array and single PCSEL device was observed. Our compact PCSEL array designs by passive lateral coupling have potential applications in fields of on-chip photonic computing, quantum, and information processing. [ABSTRACT FROM AUTHOR]

Continuum- or discrete-polarizable models for the study of optoelectronic processes in embedded subsystems rely mostly on the restriction of the surrounding electronic dielectric response to its low frequency limit. Such a description hinges on the assumption that the electrons in the surrounding medium react instantaneously to any excitation in the central subsystem, thus treating the environment in the adiabatic limit. Exploiting a recently developed embedded GW formalism with an environment described at the fully ab initio level, we assess the merits of the adiabatic limit with respect to an environment where the full dynamics of the dielectric response are considered. Furthermore, we show how to properly take the static limit of the environment's susceptibility by introducing the so-called Coulomb-hole and screened-exchange contributions to the reaction field. As a first application, we consider a C60 molecule at the surface of a C60 crystal, namely, a case where the dynamics of the embedded and embedding subsystems are similar. The common adiabatic assumption, when properly treated, generates errors below 10% on the polarization energy associated with frontier energy levels and associated energy gaps. Finally, we consider a water molecule inside a metallic nanotube, the worst case for the environment's adiabatic limit. The error on the gap polarization energy remains below 10%, even though the error on the frontier orbital polarization energies can reach a few tenths of an electronvolt. [ABSTRACT FROM AUTHOR]

The surface optical (SO) phonon replica in photoluminescence (PL) spectroscopy of nitride nanowires (NWs) was theoretically investigated in this study. The dispersive relationships of SO phonon mode in anisotropic wurtzite (WZ) and isotropic zinc-blende (ZB) crystal structure NWs with circular and square cross sections (CSs) were derived within the framework of the dielectric continuum model. Based on the energy and momentum conservation laws, a constraint relationship between the frequency and wave-number was constructed for SO phonon-assisted excitonic PL spectra in the NW structure. By combining the dispersive and constraint relationships, the frequency and wave-number of the SO phonon replica in the PL spectra could be determined. The WZ and ZB crystal structures of nitride semiconductor were considered. The influences of surface factors including the CS shape, dielectric medium, and environment temperature on the frequency and photon wavelength of the band-edge emission of the SO phonon replica were studied in detail. Numerical results reveal that the crystal structure, surface factors, and environment temperature greatly affect the frequency and photon wavelength of the band-edge emission of the SO phonon replica. The calculated results for the photon wavelength agree well with the experimental values of the SO phonon replica in AlN NWs. The results of the dielectric effect obtained here are also supported by previous experimental and theoretical results for nitrides and other semiconductor NWs. The present theoretical scheme and numerical results can be used to analyze and design the SO phonon replica in PL spectra of nanostructures. [ABSTRACT FROM AUTHOR]

Controlling triplet states is crucial to improve the efficiency and lifetime of organic room temperature phosphorescence (ORTP). Although the intrinsic factors from intramolecular radiative and non-radiative decay have been intensively investigated, the extrinsic factors that affect triplet exciton quenching are rarely reported. Diffusion to the defect sites inside the crystal or at the crystal surface may bring about quenching of triplet exciton. Here, the phosphorescence lifetime is found to have a negative correlation with the triplet exciton diffusion coefficient based on the density functional theory (DFT)/time-dependent density functional theory (TD-DFT) calculations on a series of ORTP materials. For systems with a weak charge transfer (CT) characteristic, close π–π stacking will lead to strong triplet coupling and fast triplet exciton diffusion in most cases, which is detrimental to the phosphorescence lifetime. Notably, for intramolcular donor–acceptor (D–A) type systems with a CT characteristic, intermolecular D–A stacking results in ultra-small triplet coupling, thus contributing to slow triplet diffusion and long phosphorescence lifetime. These findings shed some light on molecular design toward high-efficiency long persistent ORTP. [ABSTRACT FROM AUTHOR]

To qualify the nature of a SiO2 film grown on a Si single crystal substrate by surface oxidation, we originally propose a quartz–cristobalite (Q–C) alloy-like model of SiO2 film growth on a Si (100) substrate. We treat two types of Si–SiO2 transformations as reactions when oxidizing a Si wafer surface: Si–quartz transformation with Si emissions and Si–cristobalite transformation without Si emission. Expanding into a Q–C alloy-like model using the Hakoniwa method enables us to estimate both the ratio of Si emitting from the SiO2/Si interface among involved Si atoms in the thermally oxidized Si wafer surface and molecular volume expansion ratio from Si to SiO2. In addition, SiO2 film stress generated during oxidation is also discussed. [ABSTRACT FROM AUTHOR]

Experimental and simulation studies were conducted for surface segregation-limited kinetics of nitrogen incorporation into a 4H-SiC crystal during physical vapor transport (PVT) crystal growth. It was revealed that the nitrogen incorporation is kinetically limited by the step-flow velocity on the growing crystal surface of a 4H-SiC crystal; in this study, the surface step-flow velocity at the growth front was deduced from the local inclination angle of the growth front measured from the (000 1 ¯) plane, assuming a uniform growth rate along the c-axis (crystal growth direction) across the growth front, and the nitrogen concentration across the growth front was measured using Raman scattering microscopy. The step-flow velocity dependence of nitrogen incorporation was theoretically analyzed using a two-site-exchange model, and the simulated dependence using the model was in good agreement with the experimental data. On the basis of these experimental and simulation results, kinematical and energetical aspects of nitrogen incorporation at the growth front of a 4H-SiC crystal during PVT growth are discussed. [ABSTRACT FROM AUTHOR]

The facet-dependent adsorption of CO on oxidized and reduced CeO2 single crystal surfaces is reviewed, with emphasis on the effect of CO coverage and the ability of state-of-the-art quantum-mechanical methods to provide reliable energies and an accurate description of the IR vibrational frequency of CO. Comparison with detailed, high-resolution experimental infrared reflection absorption spectroscopy data obtained for single crystal samples allows the assignment of the different CO vibrational bands observed on all three low-index ceria surfaces. Good agreement is achieved with the hybrid density functional theory approach with the HSE06 functional and with saturation coverage. It is shown that CO is very sensitive to the structure of cerium oxide surfaces and to the presence of oxygen vacancies. The combined theoretical-experimental approach offers new opportunities for a better characterization of ceria nanoparticles and for unraveling changes occurring during reactions involving CO at higher pressures. [ABSTRACT FROM AUTHOR]

Salt solubility is generally determined under isotropic stress conditions. Yet, in the context of salt weathering of porous media, mechanical constraints on the in-pore growth of salt crystals are likely to be orientation-dependent, resulting in an anisotropic stress state on the crystal. In this paper, we determine by molecular simulation the solubility of NaCl in water when the crystal is subjected to anisotropic stress. Such anisotropy causes the chemical potential of the crystal to be orientation-dependent, and proper thermodynamic formulation requires describing the chemical potential as a tensor. The solute and crystal chemical potentials are computed from free energy calculations using Hamiltonian thermodynamic integration, and the usual condition of solubility is reformulated to account for the tensorial nature of the crystal chemical potential. We investigate in detail how the uniaxial compression of the crystal affects its solubility. The molecular simulation results led to revisiting the Correns law under anisotropic stress. Regarding the solute, the non-ideal behavior of the liquid phase is captured using Pitzer's ion interaction approach up to high concentrations of interest for in-pore crystallization and beyond the concentrations addressed in the existing literature. Regarding NaCl crystals, the validity of the generalized Gibbs–Duhem equation for a tensorial chemical potential is carefully verified, and it is found that crystallization progresses almost orthogonally to the crystal surface even under high shear stresses. Comparing uniaxial and isotropic compression highlights the major differences in solubility caused by stress anisotropy, and the revisited Correns law offers an appropriate framework to capture this phenomenon. [ABSTRACT FROM AUTHOR]

In this paper, we study terahertz generation through optical rectification in reflection at normal incidence in a dielectric nonlinear crystal. We first analyze, with a nonlinear optical model, the sample parameters (thickness, absorption at both laser and terahertz wavelengths, etc.) for which a terahertz optical rectification reflection scheme is preferable to the common transmission scheme. Then, we report our experimental observations of a reflected terahertz signal generated at the surface of a ZnTe crystal. The reflected terahertz signal shares all the characteristics of a signal generated in transmission but is not limited by absorption losses in the crystal, thereby providing a broader bandwidth. At high pump laser power, the signal exhibits saturation, which is caused by the decrease of the nonlinear susceptibility due to photocarriers generated by two-photon absorption. This reflection scheme could be of great importance for terahertz microscopy of opaque materials like, e.g., humid samples or samples exhibiting strong absorption bands or to study samples for which the transmitted signal cannot be recorded. [ABSTRACT FROM AUTHOR]

Kidney stones are a pervasive disease with notoriously high recurrence rates that require more effective treatment strategies. Herein, tartronic acid is introduced as an efficient inhibitor of calcium oxalate monohydrate (COM) crystallization, which is the most prevalent constituent of human kidney stones. A combination of in situ experimental techniques and simulations are employed to compare the inhibitory effects of tartronic acid with those of its molecular analogs. Tartronic acid exhibits an affinity for binding to rapidly growing apical surfaces of COM crystals, thus setting it apart from other inhibitors such as citric acid, the current preventative treatment for kidney stones. Bulk crystallization and in situ atomic force microscopy (AFM) measurements confirm the mechanism by which tartronic acid interacts with COM crystal surfaces and inhibits growth. These findings are consistent with in vivo studies that reveal the efficacy of tartronic acid is similar to that of citric acid in mouse models of hyperoxaluria regarding their inhibitory effect on stone formation and alleviating stone‐related physical harm. In summary, these findings highlight the potential of tartronic acid as a promising alternative to citric acid for the management of calcium oxalate nephropathies, offering a new option for clinical intervention in cases of kidney stones. [ABSTRACT FROM AUTHOR]

The crystal structure of superprotonic conductor caesium hydrogen sulfate phosphate [Cs4(HSO4)3(H2PO4)] have been analyzed using neutron diffraction methods. Additionally, its structure and surface layers have been investigated using atomic force microscopy. From the diffraction data obtained, Fourier syntheses of neutron scattering densities were calculated, and the localization of hydrogen atoms and the parameters of three types of hydrogen bonds in the crystal structure were accurately determined. Correlation of surface characteristics of samples obtained by atomic force microscopy with their crystal structure is shown. [ABSTRACT FROM AUTHOR]

[Display omitted] Organic fluorescent crystals were obtained using single-benzene-based diethyl 2,5-dihydroxyterephthalate (DDT) molecules through crystallization from a droplet of the DDT solution on an Au substrate. To control the size of the DDT crystals, the surface energy of the Au substrate was modified with air plasma treatment, producing a hydrophilic surface and a hydrophobic self-assembled monolayer (SAM) coating. The size of DDT crystals increased as the surface energy of the substrate decreased. The averaged cross-section area of the DDT crystals on the Au substrates increased in the order of the air-plasma-treated substrate (∼23.43 μm2) < pristine substrate (∼225.6 μm2) < hydrophobic SAM-coated substrate (∼2240 μm2). On the other hand, the main emission of the DDT crystals redshifted from blue to green as the crystal size increased, which is related to the aggregation of the DDT crystals. Moreover, the coffee-ring effect during the DDT crystallization was hindered by controlling the solvent evaporation conditions. As examples of the application of the proposed technique, patterned DDT crystals were obtained using selectively patterned hydrophobic and hydrophilic substrates. [ABSTRACT FROM AUTHOR]

In this paper, we propose and numerically characterize the optical characteristics of a dual eccentric-core D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) refractive index (RI) sensor. The dual eccentric-core structure can leak more power to plasma film to excite SPR phenomenon than conventional structures. We investigate the influences induce by diameter of air holes, distance between air holes and thickness of gold film. The results show that our sensor has the wavelength sensitivities (WS) of 44,000 nm/RIU for odd mode and 39,000 nm/RIU for even mode. Moreover, the sensor has the detection range of RI from 1.00 to 1.37, the maximum figure-of-merit (FOM) of 325/RIU, maximum resolution of 2.27 × 10−6 RIU for analyte RI change of 0.1 nm, and the minimum full-width at half-maximum (FWHM) of 56 nm. The sensor has wide application prospects in methane, blood plasma, and methanol detecting. [ABSTRACT FROM AUTHOR]

Photocatalytic conversion of CO 2 into fuels such as CO, CH 4 , and CH 3 OH, is a promising approach for achieving carbon neutrality. Bismuth oxyhalides (BiOX, where X = Cl, Br, and I) are appropriate photocatalysts for this purpose due to the merits of visible-light-active, efficient charge separation, and easy-to-modify crystal structure and surface properties. For practical applications, multiple strategies have been proposed to develop high-efficiency BiOX-based photocatalysts. This review summarizes the development of different approaches to prepare BiOX-based photocatalysts for efficient CO 2 reduction. In the review, the fundamentals of photocatalytic CO 2 reduction are introduced. Then, several widely used modification methods for BiOX photocatalysts are systematacially discussed, including heterojunction construction, introducing oxygen vacancies (OVs), Bi-enrichment, heteroatom-doping, and morphology design. Finally, the challenges and prospects in the design of future BiOX-based photocatalysis for efficient CO 2 reduction are examined. [Display omitted] [ABSTRACT FROM AUTHOR]

The boundary integral equation (BIE) describes the dynamics of a curved crystallization front separating liquid melt and solid material. We derive a generalized BIE for the thermal‐concentration problem taking into account the nonlinear dependence of the crystallization temperature on solute concentration and the kinetics of atomic attachment at the interface. This equation determines the evolution of the interface function and the equation for crystallization driving force ‐ the melt undercooling at the crystal surface. Our calculations carried out for a dendritic vertex in the form of a paraboloid of revolution have shown that the growth rate of the dendritic tip and its diameter substantially depend on the nonlinear effects under study. In particular, the velocity and diameter of the dendrite tip respectively become greater and narrower with increasing deviation of the liquidus equation from the linear relationship. Also, the dendrite tip velocity can be significantly affected by variations in the exponent of atomic kinetics. [ABSTRACT FROM AUTHOR]

Quantum dot-based epitaxially regrown photonic crystal surface emitting lasers are demonstrated at room temperature. The GaAs-based devices, which are monolithically integrated on the same wafer, exhibit ground state lasing at ∼1230 nm and excited state lasing at ∼1140 nm with threshold current densities of 0.69 and 1.05 kA/cm2, respectively. [ABSTRACT FROM AUTHOR]

The rapid release of gas by a chemical reaction to generate momentum is one of the most fundamental ways to elicit motion that could be used to sustain and control the motility of objects. We report that hollow crystals of a three‐dimensional supramolecular metal complex that releases gas by photolysis can propel themselves or other objects and advance in space when suspended in mother solution. In needle‐like regular crystals, the reaction occurs mainly on the surface and results in the formation of cracks that evolve due to internal pressure; the expansion on the cracked surface of the crystal results in bending, twisting, or coiling of the crystal. In hollow crystals, gas accumulates inside their cavities and emanates preferentially from the recess at the crystal terminus, propelling the crystals to undergo directional photomechanical motion through the mother solution. The motility of the object which can be controlled externally to perform work delineates the concept of "crystal microbots", realized by photoreactive organic crystals capable of prolonged directional motion for actuation or delivery. Within the prospects, we envisage the development of a plethora of light‐weight, efficient, autonomously operating robots based on organic crystals with high work capacity where motion over large distances can be attained due to the large volume of latent gas generated from a small volume of the crystalline solid. [ABSTRACT FROM AUTHOR]

The rapid release of gas by a chemical reaction to generate momentum is one of the most fundamental ways to elicit motion that could be used to sustain and control the motility of objects. We report that hollow crystals of a three‐dimensional supramolecular metal complex that releases gas by photolysis can propel themselves or other objects and advance in space when suspended in mother solution. In needle‐like regular crystals, the reaction occurs mainly on the surface and results in the formation of cracks that evolve due to internal pressure; the expansion on the cracked surface of the crystal results in bending, twisting, or coiling of the crystal. In hollow crystals, gas accumulates inside their cavities and emanates preferentially from the recess at the crystal terminus, propelling the crystals to undergo directional photomechanical motion through the mother solution. The motility of the object which can be controlled externally to perform work delineates the concept of "crystal microbots", realized by photoreactive organic crystals capable of prolonged directional motion for actuation or delivery. Within the prospects, we envisage the development of a plethora of light‐weight, efficient, autonomously operating robots based on organic crystals with high work capacity where motion over large distances can be attained due to the large volume of latent gas generated from a small volume of the crystalline solid. [ABSTRACT FROM AUTHOR]

Due to the low tolerance factor, the black-phase CsPbI3 could easily transform into the photovoltaic-inactive yellow phase under the pressure of moisture, restricting the performance and stability of corresponding solar cells. Here, Ca(CF3SO3)2 is introduced into CsPbI3 to solve this problem. The Ca2+ cations could interact with I− ions to inhibit ion migration and prevent the collapse of the perovskite structure, while the CF3SO3− anions anchoring on the crystal surface could provide hydrophobicity. Ca(CF3SO3)2 introduction, thus, increases the intrinsic and extrinsic stability of black-phase CsPbI3 simultaneously. The interaction between Ca(CF3SO3)2 and perovskite precursors retards the crystallization process and facilitates the growth of high-quality films with reduced non-radiative recombination. Moreover, the CF3SO3− anions on the surface induce p-type doping and modify the energy level alignment with the hole transport layer. Benefiting from the Ca(CF3SO3)2 introduction, the CsPbI3 all-inorganic perovskite solar cells exhibit improved power conversion efficiency (PCE) from 14.76% to 16.50%. In addition, the unencapsulated device with Ca(CF3SO3)2 retains 81% of its original PCE after storage in air for 500 h, outperforming that of the control device (65%). [ABSTRACT FROM AUTHOR]

Normally, the acidic impurities in hemihydrate phosphogypsum (HPG) must be neutralized when HPG is utilized, and a little amount of calcium hydroxide (CH) is the best choice. In this paper, the effects of excessive CH (5 wt.%, 10 wt.%, 15 wt.% and 20 wt.% of HPG) for carbonation curing on the performance of hardened HPG paste were studied. According to the results of macro tests and microanalyses of XRD, TG, SEM-EDS, MIP and N2 physisorption, it could be verified that CaF2, Ca3(PO4)2 and a large amount of nanoscale CaCO3 crystals were produced as a result of neutralization and carbonation, and the compressive strength and the water resistance of carbonated HPG + CH paste were significantly improved due to the effects of nanoscale CaCO3 crystals on pore refinement and the coverage on the surfaces of gypsum crystals of the hardened paste. Therefore, this study suggests a feasible and green method for recycling HPG/PG, with the collaborative effects of neutralization, performance enhancement and reductions in CO2 emissions. [ABSTRACT FROM AUTHOR]

We investigated the effect of Fe 50 Pd 50 nanoparticle addition on the crystal structure and superconductivity of Bi 1. 6 Pb 0. 4 Sr 2 Ca 2 Cu 3 O 10+δ compounds. Pure and Fe 50 Pd 50 -added Bi 1. 6 Pb 0. 4 Sr 2 Ca 2 Cu 3 O 10+δ samples with different additional contents were prepared by the solid-state reaction technique. Crystal structure and surface morphology of the fabricated samples revealed the formation of Bi-2223 and Bi-2212 superconducting phases. The critical temperature (T c) of the Fe 50 Pd 50 -added samples was lower than that of the pure one. In comparison with the pure sample, magnetization J c was clearly enhanced for the samples with the addition of Fe 50 Pd 50 having stronger magnetic properties. The enhancement in J c was possibly explained by the fact that Fe 50 Pd 50 nanoparticles served as effective pinning centers. Dominant pinning mechanisms of all samples were analyzed to be δl pinning by the collective pinning theory. The geometry of artificial pinning centers was identified to be normal core volume and point-like pinning by using the Dew–Hughes model. [ABSTRACT FROM AUTHOR]

We present the development of a heat flow model utilizing a scintillating crystal for heat and light detection. By analyzing the measured light signals from α - and β / γ -induced events in a CaMoO 4 crystal, we describe the time-dependent behavior of the scintillation emission and the subsequent generation of delayed phonons in the crystal. The phonon detection channel model incorporates both prompt and delayed generation of a thermal phonons; these are absorbed in a phonon collector film on the crystal surface or converted into a thermal phonon distribution in the crystal. A reasonable agreement is observed in the comparison between the measured signals and the simulated signals derived from the model study. We attribute the observed pulse shape discrimination to the presence of the delayed phonons associated with the scintillation process. [ABSTRACT FROM AUTHOR]

The effect of ZrO 2 and TiO 2 addition in gahnite-based glass-ceramic glazes was investigated by equimolar nucleating agents substituting 5 mol% SiO 2. The effect of this substitution on thermal behavior was studied by means of differential thermal analysis and hot stage microscopy. The sintering behavior of samples changed with the type of nucleating agent added. Compacted samples sintered between 850 and 1200 °C for 2 min at 40°Cmin−1 heating and cooling rate for determining the crystallization sequence with using X-ray diffraction. Prepared glaze samples fired at 1180 °C for 6 min in the industrial roller kiln. Total firing time is 58 min from cold to cold. The effect of nucleating agent additions of gahnite-based glass-ceramic glazes was investigated by X-ray diffraction, scanning electron microscopy, spectrophotometer, and gloss meter. Glaze without nucleating agents shows heterogeneous surface crystallization from the frit surface to the inside with dendritic gahnite growth. With the nucleating agent, volume crystallization was seen with phase separation or seeding effect, which depends on the type of nucleating agent. Glaze with TiO 2 has two different morphology; one region has fine gahnite crystals below 100 nm, and another region has clusters of nano gahnite crystals in flake-like morphology. ZrO 2 provides fine gahnite crystallization, which is smaller than 80 nm. While ZrO 2 added glaze is translucent, the other glazes are opaque due to different crystal sizes. It is observed that nano crystallization has a positive effect on pore swelling behavior due to its high crystal surface area. With the addition of the ZrO 2 and TiO 2 , fine-sized nanocrystalline gahnite based glass-ceramic glazes can be obtained for the first time in industrial fast-firing conditions. [ABSTRACT FROM AUTHOR]

Winchcombe is a CM chondrite that fell in England on February 28, 2021. Its rapid retrieval was well characterized. Within two polished sections of Winchcombe, terrestrial phases were observed. Calcite and calcium sulfates were found in a sample recovered from a field on March 6, 2021, and halite was observed on a sample months after its recovery from a driveway on March 2, 2021. These terrestrial phases were characterized by scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. Calcite veins crosscut the fusion crust and therefore postdate it. The calcite likely precipitated in the damp environment (sheep field) where the meteorite lay for six days prior to its retrieval. The sulfates occur on the edges of the sample and were identified as three minerals: gypsum, bassanite, and anhydrite. Given that the sulfates occur only on the sample's edges, including on top of the fusion crust, they formed after Winchcombe fell. Sulfate precipitation is attributed to the damp fall environment, likely resulted from sulfide‐derived H2S reacting with calcite within the meteorite. Halite occurs as euhedral crystals only on the surface of a polished section and exclusively in areas relatively enriched in sodium. It was likely produced by the interaction of the polished rock slice with the humid laboratory air over a period of months. The sulfates, fusion crust calcite, and halite all post‐date Winchcombe's entry into the Earth's atmosphere and showcase how rapidly meteorite falls can be terrestrially altered. [ABSTRACT FROM AUTHOR]

[Display omitted] Fine-tuning the surface structure of transition metal oxides at the atomic level is a promising way to improve the catalytic properties of materials. However, the influence of crystal surface structure on electrode reaction kinetics is still limited. In this study, we propose an in-situ synthesis strategy to obtain two-dimensional carbon/cerium oxide core–shell nanosheets by thermal decomposition of Ce-MOF nanosheets grown on the surface of carbon nanostructures, and fine-tuning the surface structure by introducing oxygen vacancies through defect engineering during the oxide nucleation process is conducted to obtain controllable exposed {1 1 1} and {1 1 0} surface CeO 2 @C composites. Both experiments and theoretical calculations show that the {1 1 0} -dominated nanocomplex (CeO 2 @C-350S) has better kinetic behavior and catalytic activity due to its abundant surface defects, which is manifested in higher active surface area, richer carrier concentration, and better promotion of diffusion and adsorption. In addition, CeO 2 @C-350S electrode has an extremely wide linear range and good stability in the electrochemical detection of nitrite. After 1000 times of the accelerated cycle experiments, CeO 2 @C-350S electrode still maintains 79.3 % of its initial current response, and recovers to 87.3 % after 10 min of stopping the test. The electrode stability is excellent, which is attributed to the clever carbon shell structure of the material. This synthesis strategy can be extended to other carbon-based oxide composite catalysts to improve the electrocatalytic performance and overall stability by adjusting the surface structure. [ABSTRACT FROM AUTHOR]

Rate maps quantify the variability of surface rates during the dissolution of crystalline matter. Recently, highly spatially resolved rate maps revealed the existence of rhythmic pulses of the material flux from the crystal surface. The mechanism underpinning this behavior is not yet understood but the two potential influencing factors are surface-controlled or transport-controlled conditions that may govern the resulting pulsating reaction kinetics in the system. In this study, we apply two numerical methods to identify the dominating mechanism of pulsating dissolution. First, the influence of solute transport is simulated using a reactive transport model, which yields dissolution rates and concentration distribution due to the flow field, i.e., extrinsic reactivity. Second, the influence of intrinsic surface reactivity inherent to the material is simulated using kinetic Monte Carlo (KMC) simulations, where the distribution of reactive sites over time is observed on an atomic scale. Local dissolution rates can be reproduced with the reactive transport model, but no kinetically effective periodic changes of the concentration gradients can be observed and no new dissolution pulses are generated. Control via periodic changes in extrinsic reactivity is thus ruled out as a governing mechanism. In contrast, pulsating dissolution is clearly observed in the KMC simulation, leading to the conclusion that the self-assembly of varying reactive surface building blocks causes the pulsating dissolution. The simulation results suggest that etch pits generate regions with a high number of steps of single crystal layers and, consequently, with sites of increased reactivity at periodic intervals. These steps move over the crystal surface outward from the pit center and are followed by a region with a low number of surface steps. Only when the steps reach a certain spacing to the center new steps are generated at the transition between the hollow core and the etch pit. This self-assembly is observed as a fundamental behavior of crystalline dissolution in KMC models, without any additional parametrization. It thus represents a fundamental mechanism in crystal dissolution and should be considered for an accurate atomic understanding of crystal dissolution. [ABSTRACT FROM AUTHOR]

Chemical weathering associated with dissolution/precipitation at interfaces between minerals and flowing fluids is key for the evolution of geologic systems, including groundwater contamination and storage capacity. Relying on Atomic Force Microscopy (AFM) yields reaction rates at nanoscale resolutions. Challenges limiting our ability to quantify heterogeneity associated with these processes include establishing reliable platforms allowing AFM imaging of real‐time and in situ absolute material fluxes across mineral surfaces under continuous flow conditions to complement typically acquired surface topography images. We provide an experimental workflow and heterogeneous absolute rates at the nanoscale across the surface of a calcite crystal under dissolution. These high‐quality experimental observations are then interpreted through a stochastic approach. The latter is geared to embed diverse kinetic modes driving the degree of spatial heterogeneity of the reaction and corresponding to different mechanistic processes documented across the crystal surface. Plain Language Summary: Quantification of basic processes underpinning precipitation/dissolution at mineral/fluid interfaces is key for realistic assessment of chemical weathering rates driving rock morphology, subsurface storage capacity and contamination. We provide direct observation of the complex mechanistic processes acting at nanoscales through an original experimental platform relying on Atomic Force Microscopy imaging to evaluate absolute material fluxes associated with dissolution of a mineral subject to reaction under continuous flow conditions. Dissolution is characterized at very high spatial resolutions (∼10 nm). This enables observing in real‐time and in situ mechanistic processes driving system evolution. The ensuing rich data set of absolute reaction rates displays a marked degree of spatial heterogeneity. The latter is then interpreted within a stochastic framework to yield a detailed mechanistic appraisal of mineral dissolution. Key Points: A platform to evaluate absolute nanoscale topographic measurements of a crystal sample subject to dissolution/precipitation is designedThe associated spatially heterogeneous fields of absolute material fluxes across the surface are evaluatedReaction rates are described through a stochastic framework encapsulating behaviors of surface features driving dissolution processes [ABSTRACT FROM AUTHOR]

Vapor sensors with both high sensitivity and broad detection range are technically challenging yet highly desirable for widespread chemical sensing applications in diverse environments. Generally, an increased surface‐to‐volume ratio can effectively enhance the sensitivity to low concentrations, but often with the trade‐off of a constrained sensing range. Here, an approach is demonstrated for NH3 sensor arrays with an unprecedentedly broad sensing range by introducing controllable steps on the surface of an n‐type single crystal. Step edges, serving as adsorption sites with electron‐deficient properties, are well‐defined, discrete, and electronically active. NH3 molecules selectively adsorb at the step edges and nearly eliminate known trap‐like character, which is demonstrated by surface potential imaging. Consequently, the strategy can significantly boost the sensitivity of two‐terminal NH3 resistance sensors on thin crystals with a few steps while simultaneously enhancing the tolerance on thick crystals with dense steps. Incorporation of these crystals into parallel sensor arrays results in ppb–to–% level detection range and a convenient linear relation between sheet conductance and semi‐log NH3 concentration, allowing for the precise localization of vapor leakage. In general, the results suggest new opportunities for defect engineering of organic semiconductor crystal surfaces for purposeful vapor or chemical sensing. [ABSTRACT FROM AUTHOR]

ZnO microcrystal arrays have been grown on a (111) silicon substrate by the vapor‒liquid‒crystal deposition, where the liquid phase is gold. The differences between the crystals obtained for growth times of 5, 10, and 15 min are described. The lattice parameters of the microcrystals have been calculated with increasing growth time: а = 3.316 Å, c = 5.281 Å; а = 3.291 Å, c = 5.270 Å; and а = 3.286 Å, c = 5.258 Å. A change in the Au content in the microcrystals during their growth has been found to vary from 0.520 at % at the substrate to 0.035 at % on the surface of the crystals after the 15-min growth. Elemental distribution maps are presented, and the deviation of the lattice parameters of the obtained crystals from the reference values is explained. [ABSTRACT FROM AUTHOR]

In this work, the dynamic behavior of nano-bubbles near the surface of single crystal iron (Fe) was investigated using molecular dynamics simulations. The cavitation erosion behavior of single crystal Fe and the structural evolution of its eroded surface was examined at different bubble diameters. The results show that nano-bubble diameter is inversely correlated with impact pressure and diameter is positively correlated with nanojet energy. The volume, surface area, and depth of cavitation pits are nearly directly proportional to the bubble diameter with correlation linear fitting coefficients of R2 = 0.9837, R2 = 0.9922, and R2 = 0.9799, respectively. Additionally, cavitation erosion induces the structural evolution of iron atoms from bcc to fcc and hcp structures. The percentage of new phase transformed is related to the bubble diameter and the type of transformed structure, the percentage of fcc and hcp structures of Fe atoms exhibits an increasing trend with the increase in the bubble diameter, and the Fe atoms of fcc structures occur an obvious increase beyond a bubble diameter of 12 nm. [ABSTRACT FROM AUTHOR]

In this paper, porous single-crystal diamond with boron doping were synthesized by adding TiB 2 to the Fe–Ni–C system at a pressure of 5.6 GPa and a temperature of 1360 °C. The boron and nitrogen impurities were investigated in depth along with the surface defects of the diamonds. The results indicate that when the TiB 2 content was within the range of 0–10 wt%, an increase in the doping concentration of TiB 2 can lead to a decrease in the nitrogen content and an increase in the boron content in the diamond, causing the crystal color to transition from yellow to pale yellow, pale yellow-blue, and black. When the TiB 2 content was within the range of 20–40 wt%, several triangular concave porous structures appeared on the crystal surface. With an increase in the TiB 2 addition, the side length of these triangular pits decreased from 2.85 μm to 1.09 μm, while their depth decreased from 590 nm to 50 nm. The roughness of the crystal surface measured by Rq demonstrated values up to 145.302 nm. The results indicate that the size, depth, and density of the triangular defects can be adjusted by the amount of additive TiB 2. Our findings provide insights into the surface regulation and functionalization of boron-doped diamond single crystals. [ABSTRACT FROM AUTHOR]

2D halide perovskites are extensively studied for optoelectronic applications owing to their outstanding excitonic performance. Studies have revealed the coexistence of the high‐temperature phase and low‐temperature phase in 2D perovskite (BA)2PbI4 flakes and the correlation between the degree of phase transition with the thickness; nevertheless, structural phase transition at surface still remains elusive. Here, the use of interlayer excitons in (BA)2PbI4/WSe2 heterojunctions to characterize its structural phase transitions at surface in (BA)2PbI4 is proposed. Two types of interlayer exciton emission caused by the phase transition of (BA)2PbI4 can be observed, which can be attributed to the low‐temperature and high‐temperature phases of (BA)2PbI4, respectively. Importantly, the spatially resolved PL mapping suggests that two phases in the coexisted region distribute rather uniformly and the degree of phase transition at the surface and interior of crystal remains largely the same. The results provide a novel and non‐destructive approach to explore the phase transition of (BA)2PbI4 and offer new route to further regulate its phase transition. [ABSTRACT FROM AUTHOR]

Palm oil is a natural source of phytonutrients such as vitamin E and carotenoids. However, these high-value compounds are lost during conventional refining. These phytonutrients can be separated and recovered from crude palm oil (CPO) through methods which prevents the degradation of these compounds. This study evaluated the integrated approach of molecular distillation and adsorption, with the aim of deacidifying and separating vitamin E and carotenoids from CPO, allowing their recovery. Wiped-film molecular distillation (WFMD) was used for deacidification and vitamin E enrichment, the best results were obtained at 200 °C and 21 mL/min. The distillate stream was enriched 937.8% in vitamin E, and the residue stream (named deacidified palm oil - DAPO), enriched in carotenoids, reached 0.1% free fatty acids (FFA). Integration with the adsorption process achieved a carotenoids removal of 79.4% from the DAPO stream. Moreover, the kinetic constant (k2) of adsorption increased by around 87% for DAPO, a result attributed to the absence of fat crystals on the adsorbent surface verified by scanning electron microscopy. Notably, the integrated process approach used is an innovative methodology for the vegetable oil industry presenting an alternative route that allows the preservation and recovery of phytonutrients, and the oil deacidification. [ABSTRACT FROM AUTHOR]

Crystal‐hosted melt embayments and melt inclusions partially record magmatic processes at depth, but it is not always obvious how to interpret this record. One impediment is our incomplete understanding of how embayments and melt inclusions form. In this study, we investigate the formation mechanism of embayments and melt inclusions during quartz growth to quantify the relationship between the compositions of the entrapped and average melt. We study the growth of embayments and inclusions through direct numerical simulations that couple the growth of a crystal surface with the evolution of the concentrations of incompatible components in the surrounding melt. We find that H2O is more enriched in the interior of defects on crystal surface compared to the exterior. The resultant lower disequilibrium in the defect interior causes lower growth rate than in the exterior, elongating the defect into an embayment. If crystal growth stops, the composition in the embayment equilibrates with the average melt within days to months. If crystal growth continues until the embayment neck closes, a melt inclusion forms. The melt entrapped by both embayments and melt inclusions is enriched in incompatible components, such as H2O and CO2. In addition to inclusion size, the enrichment of incompatible components in melt inclusions also depends on component diffusivity and the crystal growth regime. High‐diffusivity components like H2O have similar enrichment levels in all scenarios, while lower‐diffusivity components like CO2 are more enriched in melt inclusions with smaller sizes or formed in continuous crystal growth. Plain Language Summary: Embayments and melt inclusions are small droplets of melt entrapped by crystals. These droplets may contain valuable clues for understanding processes inside volcanoes inaccessible to direct observation, because they typically form at depth before the onset of eruptions. Embayments are partially connected to exterior melt and can record processes during eruption. Melt inclusions are fully isolated and can record magma compositions at depth. However, we do not yet understand how they form. Our lack of understanding hinders our ability to interpret this data. Here, we use numerical simulations to quantify how the enrichment of dissolved water in the melt near the crystal affects the formation of embayments and melt inclusions during quartz growth. There is a positive feedback between the water enrichment in the embayment interior and embayment elongation, because water is not integrated into the quartz as it grows. Our simulations put constraints on the application of embayments and melt inclusions to constrain volcanic processes: For embayments, component enrichment likely equilibrates with surrounding melt prior to eruption. For melt inclusions, high‐diffusivity components like water are similarly enriched in all scenarios, while lower‐diffusivity components like carbon dioxide are more enriched in smaller inclusions formed in continuous crystal growth. Key Points: Embayments can form from crystal defects because water is more enriched inside the defect than outsideEnrichment of incompatible components in embayments likely equilibrates in pre‐eruptive magma storageCarbon dioxide is more enriched in smaller melt inclusions formed in continuous crystal growth but water has similar enrichment in all cases [ABSTRACT FROM AUTHOR]

Minimum energy path (MEP) search is a vital but often very time-consuming method to predict the transition states of versatile dynamic processes in chemistry, physics, and materials science. In this study, we reveal that the largely displaced atoms in the MEP structures maintain transient chemical bond lengths resembling those of the same type in the stable initial and final states. Based on this discovery, we propose an adaptive semirigid body approximation (ASBA) to construct a physically reasonable initial guess for the MEP structures, which can be further optimized by the nudged elastic band method. Examination of several distinct dynamical processes in bulk, on crystal surface, and through two-dimensional system shows that our transition state calculations based on the ASBA results are robust and significantly faster than those based on the popular linear interpolation and image-dependent pair potential methods. [ABSTRACT FROM AUTHOR]

In this study, a novel MgO–C refractory, fabricated through high–temperature nitriding, was developed by incorporating Si–Al 4 SiC 4 to in–situ form plate–like Mg–sialon ceramic bonding phase in situ. The influences of Al 4 SiC 4 content and nitriding temperature on the phase transformation, microstructure, and mechanical properties of MgO–C refractories were examined. The synergistic effect of Si co–existed with Al 4 SiC 4 promoted the in–situ formation of plate–like Mg–sialon, thereby accelerating the densification of MgO–C refractories. The primary crystal growth surface for Mg–sialon was identified as the (100) facet. The plate–like Mg–sialon was integrally bonded within the matrix, enhancing the interfacial bonding with MgO particles, rather than merely adhering to the surface. The incorporation of 2 wt% Al 4 SiC 4 significantly optimized the microstructure of MgO–C refractories, culminating in superior mechanical properties when nitrided at 1400 °C. Furthermore, the formation mechanism and morphological evolution of the plate–like Mg–sialon in MgO–C refractories were explored. • Novel in–situ Mg–sialon enhanced low–carbon MgO–C refractories have been developed. • The coexistence of Si with Al 4 SiC 4 synergistically facilitated the in-situ formation of plate-like Mg-sialon. • The addition of 3 wt% Si and 2 wt% Al 4 SiC 4 demonstrated optimal properties for the novel refractories. • The thermodynamics of the nitridation process was simulated and calculated. • Mg–sialon formation occurs predominantly through a solution–precipitation mechanism. [ABSTRACT FROM AUTHOR]

GaN nanostructures are promising for a broad range of applications due to their 3D structure, thereby exposing non-polar crystal surfaces. The nature of the exposed crystal facets, i.e., whether they are a-, m-plane, or of mixed orientation, impacts the stability and performance of GaN nanostructure-based devices. In this context, it is of great interest to control the formation of well-defined side facets. Here, we show that we can control the crystal facet formation at the nanowire sidewalls by tuning the III–V ratio during selective area growth by molecular beam epitaxy. Especially, the N flux serves as a tool for controlling the growth kinetics. In addition, we demonstrate the growth of GaN nanofins with either a- or m-plane side facets. Based on our observations, we present the underlying nanostructure growth mechanisms. Low temperature photoluminescence measurements show a correlation of the formation of structural defects like stacking faults with the growth kinetics. This article demonstrates the controlled selective epitaxy of GaN nanostructures with defined crystal side facets on large-scale available AlN substrates. [ABSTRACT FROM AUTHOR]

Dendrites growth and unstable interfacial Li+ transport hinder the practical application of lithium metal batteries (LMBs). Herein, we report an active layer of 2,4,6–trihydroxy benzene sulfonyl fluorine on copper substrate that induces oriented Li+ deposition and generates highly crystalline solid‐electrolyte interphase (SEI) to achieve high‐performance LMBs. The lithiophilic −SO2− groups of highly crystalline SEI accept the rapidly transported Li+ ions and form a dense inner layer of LiF and Li3N, which regulate Li+ plating morphology along the (110) crystal surface toward dendrite‐free Li anode. Thus, Li||Cu cells with lithiophilic SEI achieve an average deposition efficiency of 99.8 % after 700 cycles, and Li||Li cells operate well for 1100 h. Besides, Li||LiNi0.8Co0.1Mn0.1O2 cells with modified SEI exhibit a capacity retention that is 14 times than that of conventional SEI. Even at −60 °C, Li||Cu cells reach stable deposition efficiency of 83.2 % after 100 cycles. [ABSTRACT FROM AUTHOR]

Dendrites growth and unstable interfacial Li+ transport hinder the practical application of lithium metal batteries (LMBs). Herein, we report an active layer of 2,4,6–trihydroxy benzene sulfonyl fluorine on copper substrate that induces oriented Li+ deposition and generates highly crystalline solid‐electrolyte interphase (SEI) to achieve high‐performance LMBs. The lithiophilic −SO2− groups of highly crystalline SEI accept the rapidly transported Li+ ions and form a dense inner layer of LiF and Li3N, which regulate Li+ plating morphology along the (110) crystal surface toward dendrite‐free Li anode. Thus, Li||Cu cells with lithiophilic SEI achieve an average deposition efficiency of 99.8 % after 700 cycles, and Li||Li cells operate well for 1100 h. Besides, Li||LiNi0.8Co0.1Mn0.1O2 cells with modified SEI exhibit a capacity retention that is 14 times than that of conventional SEI. Even at −60 °C, Li||Cu cells reach stable deposition efficiency of 83.2 % after 100 cycles. [ABSTRACT FROM AUTHOR]

Polyiodides present high bonding flexibility already at ambient conditions, and undergo significant pressure-induced structural deformations. Resonant Raman spectroscopy has been widely used to study I–I bonds in various polyiodides, but it carries a risk of photodecomposition due to the high visible-light absorption of iodine. In this study, tetraethylammonium (bis)diiodine triiodide (TEAI) has been investigated by resonant Raman spectroscopy up to 12.02(3) GPa. The effect of pressure on the intensities and positions of Raman bands has been evaluated and correlated with the interatomic I–I distances derived from high-pressure X-ray diffraction experiments. Pressure was shown to effectively stabilize TEAI against laser-induced photodecomposition, even after a long course of irradiation with the resonant laser light. Examination of a freshly exposed crystal surface revealed that TEAI superficially passivates with the layer of lower polyiodides, which prevents further iodine loss, and shows distinct pressure-induced behaviour. [ABSTRACT FROM AUTHOR]

Precisely introducing topological defects is an important strategy in nanographene crystal engineering because defects can tune π‐electronic structures and control molecular assemblies. The synergistic control of the synthesis and assembly of nanographenes by embedding the topological defects to afford two‐dimensional (2D) crystals on surfaces is still a great challenge. By in‐situ embedding ladder bipyrazinylene (LBPy) into acene, the narrowest nanographene with zigzag edges, we have achieved the precise preparation of 2D nonbenzenoid heteroacene crystals on Au(111). Through intramolecular electrocyclization of o‐diisocyanides and Au adatom‐directed [2+2] cycloaddition, the nonbenzenoid heteroacene products are produced with high chemoselectivity, and lead to the molecular 2D assembly via LBPy‐derived interlocking hydrogen bonds. Using bond‐resolved scanning tunneling microscopy, we determined the atomic structures of the nonbenzenoid heteroacene product and diverse organometallic intermediates. The tunneling spectroscopy measurements revealed the electronic structure of the nonbenzenoid heteroacene, which is supported by density functional theory (DFT) calculations. The observed distinct organometallic intermediates during progression annealing combined with DFT calculations demonstrated that LBPy formation proceeds via electrocyclization of o‐diisocyanides, trapping of heteroarynes by Au adatoms, and stepwise elimination of Au adatoms. [ABSTRACT FROM AUTHOR]

Precisely introducing topological defects is an important strategy in nanographene crystal engineering because defects can tune π‐electronic structures and control molecular assemblies. The synergistic control of the synthesis and assembly of nanographenes by embedding the topological defects to afford two‐dimensional (2D) crystals on surfaces is still a great challenge. By in‐situ embedding ladder bipyrazinylene (LBPy) into acene, the narrowest nanographene with zigzag edges, we have achieved the precise preparation of 2D nonbenzenoid heteroacene crystals on Au(111). Through intramolecular electrocyclization of o‐diisocyanides and Au adatom‐directed [2+2] cycloaddition, the nonbenzenoid heteroacene products are produced with high chemoselectivity, and lead to the molecular 2D assembly via LBPy‐derived interlocking hydrogen bonds. Using bond‐resolved scanning tunneling microscopy, we determined the atomic structures of the nonbenzenoid heteroacene product and diverse organometallic intermediates. The tunneling spectroscopy measurements revealed the electronic structure of the nonbenzenoid heteroacene, which is supported by density functional theory (DFT) calculations. The observed distinct organometallic intermediates during progression annealing combined with DFT calculations demonstrated that LBPy formation proceeds via electrocyclization of o‐diisocyanides, trapping of heteroarynes by Au adatoms, and stepwise elimination of Au adatoms. [ABSTRACT FROM AUTHOR]

Electrocatalytic full water splitting is still a challenge. Porous single-crystalline (PSC) has a long-range ordered crystal structure and large specific surface area, which has great potential to be applied in the fields of catalysis and energy storage. Nitride single-crystalline possesses unsaturated coordination of metal-nitrogen active sites on the crystal surface, which has shown excellent performance in the electrocatalytic field. PSC tungsten nitride mesoporous nanosheets are grown from single-crystalline (SC) WO 3 nanosheets and are applied as bifunctional electrocatalysts in Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER). The overpotential of mesoporous W 2 N and WN single-crystalline nanosheets in HER is as low as 67.44 mV and 84.26 mV at a current density of 10 mA cm−2, respectively. A low overpotential has been found in PSC W 2 N and WN as the OER electrocatalyst. The PSC tungsten nitride mesoporous nanosheets provide a simple and effective solution for efficient water splitting electrocatalysts. [Display omitted] • Porous tungsten nitride single-crystalline nanosheets synthesized for the first time. • Porous single-crystalline W 2 N possesses large specific surface area. • Porous single-crystalline W 2 N has excellent HER performance. • Porous single-crystalline shows outstanding long-term durability at HER and OER. [ABSTRACT FROM AUTHOR]

The red Hare's Fur glazed bowls of the Jin and Yuan periods(1115–1368 A.D.) were analysed by optical microscopy, EDXRF, XRD, SEM-EDS, Micro-Raman spectroscopy and thermal expansion instrument. We also conduct simulation experiments at different temperatures and atmospheres. The results revealed that the Fe 2 O 3 content of the Hare's Fur glaze was about 5%. ε-Fe 2 O 3 was found in the crystals on the glaze surface. The ε-Fe 2 O 3 was all found on the rim of the bowl and it can exceed 10 µm in size. They were fired at about 1250 °C in a reducing atmosphere. The simulation experiments showed that ε-Fe 2 O 3 was formed in the cooling stage and needed to be held for a period of time at about 1160–1190 °C. The presence of mullite will promote the formation of ε-Fe 2 O 3. This is because the Al-substitution effect changes the crystal structure of ε-Fe 2 O 3 and makes it more stable. • The red Hare's Fur glazed bowls from the Dongxi Street site were fired at about 1250°C in a reducing atmosphere. • The ε-Fe 2 O 3 in the red Hare's Fur bowls was all found on the rim of the bowl and it can exceed 10 microns in size. • The ε-Fe 2 O 3 was formed in the cooling stage and needed to be held for a period of time at about 1160-1190°C. • The presence of mullite at the rim will promote the formation of ε-Fe 2 O 3. [ABSTRACT FROM AUTHOR]

By using electrolytic hydrogen peroxide (H2O2) solution, oxidation and H-termination processes were applied to the p-Si crystal surface, which will be used for Cu/p-Si Schottky contact production, in a selective and controlled manner. Before the oxidation and H-termination processes, the p-Si(100) wafer used in this study was subjected to conventional chemical cleaning, and ohmic contact was made using pure aluminum (99.99%) metal on its back surface. The p-Si/Al with ohmic back contact was divided into three parts. A rectifying contact was immediately made to the front surface of one of them by using pure copper (99.98%) metal and called the REF (Reference) sample. The front surface of one of the remaining two p-Si/Al parts was oxidized, and the front surface of the other was H-Terminated. Rectifier contacts were made for both using pure copper (99.98%) metal and were named MIS (metal-insulator-semiconductor) and SP (surface passivated), respectively. Current-voltage (I-V) measurements of Schottky diodes of REF, MIS, and SP samples were performed at room temperature and in the dark. From the obtained data, the ideality factor (n), barrier height (Φbo), and series resistance (Rs) values of the samples were determined. As a result of the investigations, it was observed that the surface oxidation and H-Termination processes caused a decrease in the rectification factor and Φbo values of MIS and SP samples. These interesting situations were interpreted by the double-layer theory, which Bardeen predicted could exist on the surface of a semiconductor crystal and contribute to its work function. [ABSTRACT FROM AUTHOR]

The title molecule, [Fe2(C5H5)2(C23H17ClN2)]⋅C3H7NO, is twisted end to end and the central N/C/N unit is disordered. In the crystal, several C--H…π(ring) interactions lead to the formation of layers, which are connected by further C--H…π(ring) interactions. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H…H (60.2%) and H… C/C…H (27.0%) interactions. Hydrogen bonding, C--H…π(ring) interactions and van der Waals interactions dominate the crystal packing. [ABSTRACT FROM AUTHOR]

Our understanding of quantum materials is commonly based on precise determinations of their electronic spectrum by spectroscopic means, most notably angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy. Both require atomically clean and flat crystal surfaces, which are traditionally prepared by in situ mechanical cleaving in ultrahigh vacuum chambers. We present a new approach that addresses three main issues of the current state-of-the-art methods: (1) Cleaving is a highly stochastic and, thus, inefficient process; (2) fracture processes are governed by the bonds in a bulk crystal, and many materials and surfaces simply do not cleave; and (3) the location of the cleave is random, preventing data collection at specified regions of interest. Our new workflow is based on focused ion beam machining of micro-strain lenses, in which shape (rather than crystalline) anisotropy dictates the plane of cleavage, which can be placed at a specific target layer. As proof-of-principle, we show ARPES results from micro-cleaves of Sr2RuO4 along the ac plane and from two surface orientations of SrTiO3, a notoriously difficult to cleave cubic perovskite. [ABSTRACT FROM AUTHOR]

A new ε-polymorph of 4,4,5,5-tetramethyl-2-(4-nitrophenyl)-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl is prepared and characterized by single-crystal XRD. The arrays of XRD data have been accumulated and the structures of known α–γ-polymorphs of this paramagnetic are solved under the same conditions. The Hirshfeld surfaces of the crystal structures of the studied polymorphs are analyzed qualitatively and quantitatively. It is shown that the known α–δ-polymorphs contain a supramolecular associate in the form of a centrosymmetric dimer whose molecules are connected by C–H⋯O hydrogen bonds. At the same time, only the ε-polymorph contains π-bonded infinite stacks of nitrophenyl substituents, which in turn determine the formation of short distances between oxygen atoms of nitroxide groups (3.508(2) Å and 3.627(2) Å). [ABSTRACT FROM AUTHOR]

Metal halide perovskite single crystals are promising for diverse optoelectronic applications. As a universal issue of solution‐grown perovskite single crystals, surface contamination causes adverse effect on material properties and device performance. Herein, learning from the self‐cleaning effect of lotus leaf, we address the surface contamination issue by introducing an amphiphilic long‐chain organic amine into the perovskite crystal growth solution. Self‐assembly of CTAC provides a hydrophobic crystal surface, inducing spontaneous removal of residual growth solution, which results in clean surface and better optoelectronic properties of perovskite single crystals. An impressive efficiency of 23.4 % is obtained, setting a new record for FAxMA1‐xPbI3 single‐crystal perovskite solar cells (PSCs). Moreover, our strategy also applies to perovskite single crystals with different morphology and composition, which may contribute to improvement of other single‐crystal perovskite optoelectronic devices. [ABSTRACT FROM AUTHOR]

Metal halide perovskite single crystals are promising for diverse optoelectronic applications. As a universal issue of solution‐grown perovskite single crystals, surface contamination causes adverse effect on material properties and device performance. Herein, learning from the self‐cleaning effect of lotus leaf, we address the surface contamination issue by introducing an amphiphilic long‐chain organic amine into the perovskite crystal growth solution. Self‐assembly of CTAC provides a hydrophobic crystal surface, inducing spontaneous removal of residual growth solution, which results in clean surface and better optoelectronic properties of perovskite single crystals. An impressive efficiency of 23.4 % is obtained, setting a new record for FAxMA1‐xPbI3 single‐crystal perovskite solar cells (PSCs). Moreover, our strategy also applies to perovskite single crystals with different morphology and composition, which may contribute to improvement of other single‐crystal perovskite optoelectronic devices. [ABSTRACT FROM AUTHOR]