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Scandium Molybdate Microstructures with Tunable Phase and Morphology: Microwave Synthesis, Theoretical Calculations, and Photoluminescence Properties
摘要： In this paper, scandium molybdate microstructures have been prepared from solution via a microwave heating method. By controlling the experimental parameters such as molar ratio of reagent and reaction time, scandium molybdates with tunable phase and diverse morphologies including snowflakes, microflowers, microsheets, and branched spindles were obtained. The density of states and surface energies of Sc2Mo3O12 were primarily studied from first-principles calculations. An indirect band gap of 3.56 eV was observed for crystalline Sc2Mo3O12, and the surface energies of various facets were determined to be 0.27–0.91 J/m2. The influence of n(Sc3+):n(Mo7O24 6?) (short for Sc/Mo) molar ratio was systematically investigated and well-characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and UV–vis absorption spectroscopy (UV–vis). Results indicate that the Sc/Mo molar ratio has a great effect on the phase and morphology. Diffuse reflection spectra (DRS) revealed the Egap can be readily tuned from 3.69 to 4.16 eV, which is in accordance with the theoretical result. The photoluminescence (PL) properties of Eu3+-doped Sc2Mo3O12 were discussed. This facile synthesis strategy could be extended to the synthesis of other molybdates.
关键词： photoluminescence,morphology control,microwave synthesis,scandium molybdate,density functional theory
更新于2025-09-23 15:23:52
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - The structure of Scandium thin films on the W(100) surface observed using emission microscopy
摘要： Thermionic emission microscopy is used to observe scandium on W(100). Scandium thin films were deposited by thermal evaporation from a metal source onto W(100). The scandium films on W(100) were observed to de-wet from the W(100) surface and to form droplets when the surface is heated: the dewetting temperature is thickness dependent, and spans a range from 500 to 800 C, far below the melting temperature (1541 C). Thinner films produce smaller droplets.
关键词： thermionic,dewetting,scandium,emission,tungsten
更新于2025-09-23 15:21:21
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Electronic transport in degenerate (100) scandium nitride thin films on magnesium oxide substrates
摘要： Scandium nitride (ScN) is a degenerate n-type semiconductor with very high carrier concentrations, low resistivity, and carrier mobilities comparable to those of transparent conducting oxides such as zinc oxide. Because of its small lattice mismatch to gallium nitride (GaN), <1%, ScN is considered a very promising material for future GaN based electronics. Impurities are the source of the degeneracy. Yet, which specific impurities are the cause has remained in contention. ScN thin films of various thicknesses were grown on magnesium oxide substrates in a (001) orientation using reactive magnetron sputtering across a range of deposition conditions. X-ray diffraction was used to verify crystal orientation. Film thicknesses ranging from 39 to 85 nm were measured using scanning electron microscopy. The electronic transport properties of the films were characterized using Hall-effect measurements at temperatures ranging from 10 to 320 K. At 10 K, the electron concentration varies from 4.4 (cid:2) 1020 to 1.5 (cid:2) 1021 cm(cid:3)3, resistivity from 2.1 (cid:2) 10(cid:3)4 to 5.0 (cid:2) 10(cid:3)5 X(cid:4)cm, and Hall mobility from 66 to 97 cm2/V(cid:4)s. Secondary ion mass spectroscopy (SIMS) was used to determine film compositions. Finally, density functional theory (DFT) was used to compute the activation energies for various point defects including nitrogen and scandium vacancies and oxygen and fluorine substituting for nitrogen. For both oxygen and fluorine substitution, the energies were negative, indicating spontaneous formation. Nevertheless, the combined results of the Hall, SIMS, and DFT strongly suggest that oxygen substitution is the primary mechanism behind the high carrier concentration in these samples.
关键词： degenerate n-type semiconductor,Hall-effect measurements,Scandium nitride,density functional theory,electronic transport properties
更新于2025-09-23 15:21:21
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Evaluation of the Efficacy of Erbium, Chromium-doped Yttrium, Scandium, Gallium, and Garnet Laser in Partial Pulpotomy in Permanent Immature Molars: A Randomized Controlled Trial
摘要： Introduction: The use of the erbium, chromium-doped yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser in vital pulp therapy contributes to the formation of dentin bridges and a sterile zone as well as the maintenance of the vitality of the pulp. However, no prior studies have used the Er,Cr:YSGG laser in partial pulpotomy of immature permanent teeth. The aim of this study was to compare the ef?cacy of partial pulpotomy treatment using mineral trioxide aggregate (MTA) alone and MTA with the Er,Cr:YSGG laser in permanent immature molars. Methods: A total of 90 caries-exposed permanent immature molar teeth were included and randomly divided into 2 groups: the MTA group (n 5 45) and the laser 1 MTA group (n 5 45). In the MTA group, MTA was applied to the exposed area on the pulp after bleeding control. In the same session, the tooth was restored with a composite resin. In the laser 1 MTA group, before MTA condensation, the Er,Cr:YSGG laser was applied to the exposure area. Patients were recalled at 1, 3, 6, and 12 months after treatment. The Mann-Whitney U and chi-Square tests were used for statistical analysis. Results: The success rate (95.5%) of the laser 1 MTA group was similar to that of the MTA group (88.8%). There was no signi?cant difference between groups in terms of the frequency of at least 1 pathologic clinical or radiographic failure at 12 months (P . .05). Conclusions: Partial pulpotomy treatment showed a high success rate in immature permanent molars; however, the use of the laser did not contribute to the success rate compared with MTA alone.
关键词： mineral trioxide aggregate,partial pulpotomy,Erbium, chromium-doped yttrium, scandium, gallium, and garnet laser,immature teeth
更新于2025-09-23 15:21:01
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Structure and Electron Mobility of ScN Films Grown on α-Al2O3(1 1 ˉ 02) Substrates
摘要： Scandium nitride (ScN) films were grown on α-Al2O3(1102) substrates using the molecular beam epitaxy method, and the heteroepitaxial growth of ScN on α-Al2O3(1102) and their electric properties were studied. Epitaxial ScN films with an orientation relationship (100)ScN || (1102)α-Al2O3 and [001]ScN || [1120]α-Al2O3 were grown on α-Al2O3(1102) substrates. Their crystalline orientation anisotropy was found to be small. In addition, [100] of the ScN films were tilted along [1101] of α-Al2O3(1102) in the initial stage of growth. The tilt angle between the film growth direction and [100] of ScN was 1.4–2.0? and increased with growth temperature. The crystallinity of the ScN films also improved with the increasing growth temperature. The film with the highest Hall mobility was obtained at the boundary growth conditions determined by the relationship between the crystallinity and the nonstoichiometric composition because the film with the highest crystallinity was obtained under the Sc-rich growth condition. The decreased Hall mobility with a simultaneous improvement in film crystallinity was caused by the increased carrier scattering by the ionized donors originating from the nonstoichiometric composition.
关键词： heterostructure,electric property,scandium nitride,thin film
更新于2025-09-19 17:15:36
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Malpositioned canine treatment with autotransplantation and laser
摘要： Children and young adults often have tooth loss due to congenital tooth deficiency, trauma, or caries. Autotransplantation has many benefits. The transplanted tooth can be moved orthodontically, maintains alveolar bone growth potential during eruption, and functional periodontal ligament function also permits tooth eruption, allows the defected areas to be filled with the bones; gingival contour is much more successful than the one obtained with prosthesis. In this paper, treatment steps and follow?up results of autotransplantation case supported with biostimulation are mentioned. A 14?year?old female patient was admitted to the clinic with a complaint of decayed tooth 53 and malposed tooth 13. Mobile primary tooth was pulled out, and the socket was shaped with surgical drills. By performing transplantation of ectopic canine, splint was applied with steel wire and composite. Diode laser was used to provide deep disinfection of canals. The patient underwent low-dose laser therapy for biostimulation immediately after these procedures. We did not encounter any ankylosis, root resorption, periodontal, or functional problems in our evaluation with computed tomography after 3 years follow-up of the patient.
关键词： erbium,biostimulation,Autotransplantation,diode laser,chromium:yttrium-scandium-gallium-garnet
更新于2025-09-16 10:30:52
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Infrared-laser based characterization of the pyroelectricity in AlScN thin-films
摘要： A measurement system for characterization of the pyroelectricity in thin- and thick-films is introduced. The system is based on a quantum-cascade infrared laser that stimulates the temperature within the sample film with variable modulation frequencies up to 120 kHz. As model material system we choose Scandium-doped Aluminum Nitride (AlScN) due to its promising piezo- and dielectric behavior as well as CMOS compatibility. We measured the pyro-electric response and its temperature characteristics. The transverse effective piezoelectric coefficient e31 is derived from the measurement of the longitudinal effective piezoelectric modulus d33 and we discuss the contribution of piezoelectric clamping to the measured pyroelectric response. Our findings are important for integration of AlScN films on exposed membranes for dense and sensitive infrared detectors.
关键词： Pyroelectric,AlScN,Piezoelectric,Aluminum-scandium-nitride
更新于2025-09-11 14:15:04
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Stabilization of cubic phase in scandium-doped zirconia nanocrystals synthesized with sol-gel method
摘要： A new room-temperature synthesis of nanocrystals of scandium doped zirconium oxide by sol-gel method is reported. The structure of the obtained product is checked with standard structural analysis methods. The crystal phase of ZrO2-Sc2O3 nanocrystals changes from monoclinic to tetragonal and cubic with the increase in scandium concentration. The importance of the cubic phase, which appears at 10 mol% and refines at 16 mol% of Sc2O3 concentration, is emphasized. The UV-Vis absorption spectra of the product are measured, and its bandgap is evaluated from the fundamental absorption edge. The value of the bandgap was calculated as 5.65 eV for the cubic phase.
关键词： scandium-doped zirconia nanocrystals,UV-Vis spectra,sol-gel synthesis,stabilization of cubic phase
更新于2025-09-11 14:15:04
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Negative Thermal Expansion Near the Precipice of Structural Stability in Open Perovskites
摘要： Negative thermal expansion (NTE) describes the anomalous propensity of materials to shrink when heated. Since its discovery, the NTE effect has been found in a wide variety of materials with an array of magnetic, electronic and structural properties. In some cases, the NTE originates from phase competition arising from the electronic or magnetic degrees of freedom but we here focus on a particular class of NTE which originates from intrinsic dynamical origins related to the lattice degrees of freedom, a property we term structural negative thermal expansion (SNTE). Here we review some select cases of NTE which strictly arise from anharmonic phonon dynamics, with a focus on open perovskite lattices. We find that NTE is often present close in proximity to competing structural phases, with structural phase transition lines terminating near T=0 K yielding the most prominent displays of the SNTE effect. We further provide a theoretical model to make precise the proposed relationship among the signature behavior of SNTE, the proximity of these systems to structural quantum phase transitions and the effects of phase fluctuations near these unique regions of the structural phase diagram. The effects of compositional disorder on NTE and structural phase stability in perovskites are discussed.
关键词： structural phase transition,negative thermal expansion,perovskite,scandium trifluoride,antiferrodistortive phase transition,quantum phase transition,structural negative thermal expansion
更新于2025-09-04 15:30:14