- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Growth Promotion of Targeted Crystal Face by Nano-Processing via Laser Ablation
摘要： Control of crystal shape is an indispensable step for various applications of crystalline products. However, obtaining the desired crystal shape by conventionally tuning environmental conditions (temperature, additives, etc.) cannot always be reached. Recently, we have developed an innovative approach for spatiotemporal control of crystal growth of proteins and amino acids by locally modifying crystal structure (e.g., formation of screw dislocations) via femtosecond (fs) laser ablation. In this work, to clarify the appropriate laser condition for controlling the shape of single crystals with minimized damage, we first systematically investigated the dependence of pulse duration on laser ablation and crystal growth of L-phenylalanine (L-Phe). By using a laser system with tunable pulse durations from fs to nanosecond (ns), we found fs laser ablation can offer nanometer-sized, sharp etching of which diameter was smaller than the diffraction limit. By utilizing such nano-processing via fs laser ablation for promoting the growth of a targeted crystal face, we successfully demonstrated the preparation of a bulky crystal of L-Phe, which are difficult to be obtained by conventional crystallization methods.
关键词： L-phenylalanine,nano-processing,single crystal growth,crystal shape control,femtosecond laser ablation
更新于2025-09-11 14:15:04
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - A 290 W Radially Polarized Output Power from a Single-Stage Single-Crystal Yb:YAG Amplifier
摘要： Radially polarized beams exhibit interesting properties for material processing, as well as for different scientific applications such as optical trapping, plasmon excitation or data storage. With a thin-disk multipass amplifier radially polarized ultra-short pulses with an average output power of 635 W were demonstrated in [1]. For 100 W class operation, single-crystal fiber (SCF) amplifiers are an alternative approach to the thin-disk architecture. This approach reduces the costs and the complexity of the overall laser system significantly. The highest average output power demonstrated with an SCF amplifier was 160 W for a linearly polarized Gaussian seed beam [2] and 85 W for a ring-shaped radially polarized seed beam [3]. In this contribution, we present the amplification of a ring-shaped radially polarized seed beam in a single-stage SCF amplifier to an average output power of 290 W in continuous-wave (CW) operation and 270 W in femtosecond pulsed operation. This is, to the best of our knowledge, the highest average output power of a radially polarized beam demonstrated so far with an SCF amplifier.
关键词： femtosecond pulses,Radially polarized beams,high power lasers,single-crystal fiber amplifiers
更新于2025-09-11 14:15:04
-
Scintillation properties and increased vacancy formation in cerium and calcium co-doped yttrium aluminum garnet
摘要： Co-doping with divalent elements is known to improve the light yield and decay times of some cerium-activated scintillators, despite the stabilization of tetravalent Ce4+, previously believed to be non-luminescent, from the Ce3+ state. Ce4+ stabilization is a charge compensation mechanism which results from divalent ion substitution of a 3 + site. To elucidate the underlying mechanisms, which remain poorly understood, we have grown three Ce,Ca:YAG crystals with di?erent amounts of calcium co-dopants by the Czochralski method and characterized their scintillation and defect properties. Calcium co-doping reduces the decay times and stabilizes the formation of Ce4+ as expected. Interestingly, X-ray ?uorescence analysis reveals a decreased concentration of cerium within the YAG crystal for the sample doped with high levels of Ca, which could contribute to the observation that scintillator properties are improved only for low levels of Ca co-doping. Additionally, positron annihilation spectroscopy reveals an increase in the concentration of vacancies with increasing Ca concentration, while thermoluminescence is observed to show no detectable signal. Furthermore, room temperature photo-luminescence of the Ce 4f to 5d1 transition demonstrates decreased emission with increasing Ca co-doping. These data suggest that Ca co-doping decreases the decay time by creating defects with non-radiative decay pathways.
关键词： A2. Czochralski method,B2. Scintillator materials,A2. Single crystal growth,A1. Defects,B3. Scintillators,A1. Doping
更新于2025-09-11 14:15:04
-
Study of indium and antimony incorporation into SnS2 single crystals
摘要： Pure SnS2, 5% In-doped SnS2, 15% In-doped SnS2, 5% Sb-doped SnS2 and 15% Sb-doped SnS2 single crystals are grown in closed sealed quartz ampoule by direct vapour transport technique. The energy dispersive analysis of X-rays analysis of all the five as-grown single crystals showed them to be stoichiometric. The X-ray diffraction analysis showed that all the crystals are single phase possessing a hexagonal structure with (001) preferential orientation. The surface morphology of as-grown single crystals studied by scanning electron microscopy and optical microscopy showed crystal growth is by layer growth mechanism supported by screw dislocation. Selected area electron diffraction showed hexagonal spot pattern confirming the single crystalline nature of the crystals. Optical bandgap of the as-grown crystals determined by UV-Vis-NIR spectroscopy showed that the single crystals possess direct optical bandgap and the value varied between 1.89 and 2.31 eV. The photoluminescence spectra study showed the presence of six peaks. The Raman spectra showed SnS2 type the A1g vibrational mode and shifting in A1g vibrational mode with In and Sb doping. The results are elaborated in details.
关键词： Single crystal growth,Doping,Characterization,Crystal morphology,X-ray diffraction,Crystal structure
更新于2025-09-10 09:29:36
-
MORPHOLOGY OF DIAMOND SINGLE CRYSTALS GROWN IN THE Fe-Co-Mg-C SYSTEM
摘要： Diamond single crystals in a Fe-Co alloy with addition of 5 and 10 wt. % Mg by temperature gradient method were grown and their morphology was studied. For crystals obtained in the Fe-Co alloy with 5 wt. % Mg, the faces of octahedron, cube, rhomb-dodecahedron and tetragon-trioctahedron {311} were observed. When the magnesium content in the solvent-alloy increase up to 10 wt. % under the same growth conditions the tetragon-trioctahedron {311} faces on diamond crystals were absent. The topography of diamond crystals faces grown in different systems indicates that octahedron and cube are active growth forms with their growth pyramids, and rhomb-dodecahedron and tetragon-trioctahedron {311} are forms of passive growth.
关键词： A1.Crystal morphology,B1. Diamond,A2. Single crystal growth,A2. Growth from high temperature solutions
更新于2025-09-10 09:29:36
-
Argyrodite-Type Cu <sub/>8</sub> GeSe <sub/> 6- <i>x</i> </sub> Te <i> <sub/>x</sub></i> (0 ≤ <i>x</i> ≤ 2): Temperature-Dependent Crystal Structure and Thermoelectric Properties
摘要： Substitution of Se by Te in argyrodite-like Cu8GeSe6 leads to compounds Cu8GeSe6–xTex (0 (cid:2) x (cid:2) 2) and involves a structure change from the Cu8GeSe6 type to the Ag8GeTe6 type. The crystal structure of Cu8GeSe4.25Te1.75 between 50 °C and 500 °C reveals pronounced disorder of Cu atoms that is best described by anharmonic atomic displacement parameters using the Gram-Charlier expansion. Diffusion pathways are visualized by isosurfaces of joint probability density functions. The lattice parameter a increases with temperature in two linear regimes from 10.4682(18) ? to 10.609(3) ? with a superionic transition at 400 °C. The potential barrier for Cu is about 90 meV at 50 °C, which is in the range of typical ion conductors. Cu8GeSe4Te2 exhibits a higher thermoelectric figure of merit (zT = 0.65 at 350 °C) than Cu8GeSe6 (zT = 0.2 at 350 °C). The application of an effective mass model reveals that the charge carrier concentration of 6 (cid:3) 1020 cm–3 is close to optimum. In addition, argyrodite-type precipitates form heterostructures with a Cu- and Se-doped matrix of germanium antimony tellurides in the quinary system Cu/Ge/Sb/Se/Te, whose transport properties were characterized.
关键词： Single crystal,Argyrodite,Thermoelectrics,Synchrotron diffraction,Tellurium,PLEC
更新于2025-09-10 09:29:36
-
Single-Crystal MoO3 Micrometer and Millimeter Belts Prepared from Discarded Molybdenum Disilicide Heating Elements
摘要： Single-crystal MoO3 micrometer to millimeter even centimeter belts were prepared via a novel route of oxidizing a discarded molybdenum disilicide heating element at 1000 °C for 3 h. The morphology and structure features, and growth mechanism of the products were evidently investigated by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results indicated that the powdery and fibrous products were typical α-MoO3 belt-like structures which size could develop from micrometer to several millimeter even centimeter in length and up to 0.5 mm in width. It should be formed preferentially along the [001] direction via layer by layer growth to form 1-D single MoO3 belts by vapor-solid mechanism. Thermal and luminescence properties of the products were revealed by thermogravimetric analysis and differential thermal analysis and photoluminescence spectra that the resultant α-MoO3 belts had good thermal stability and characteristics of luminescence with a central peak at 481 nm. The MoO3 belts are of good potential being applied to luminescent and high temperature devices.
关键词： Single-crystal MoO3,heating element,luminescence,oxidation,molybdenum disilicide
更新于2025-09-10 09:29:36
-
Preparation and some properties of Mg <sub/>2</sub> Si <sub/>0.53</sub> Ge <sub/>0.47</sub> single crystal and Mg <sub/>2</sub> Si <sub/>0.53</sub> Ge <sub/>0.47</sub> pn-junction diode
摘要： This paper reports the results on fabrication methodology and photoresponse characteristics of Mg2Si0.53Ge0.47 pn-junction photodiode. At first, we have grown a Mg2Si0.53Ge0.47 single crystal with the Vertical Bridgman growth process. The grown crystal was characterized structurally and electrically by XRD, Laue, and Hall Effect measurements. XRD revealed the single-phase composition, Mg2Si0.53Ge0.47, of the grown crystal ingot. The clear Laue symmetrical diffraction pattern showed the single crystalline nature of the grown crystal. The Hall Effect measurement revealed the n-type conduction and the moderate Hall mobility (258 cm2/Vs), electrical resistivity (6.03E-02 ?. cm), and carrier density (4.02E+17 cm-3) of the grown crystal. Such carrier density is low enough to allow depletion region formation in case of pn-junction diodes. In that sense, we have made up for the first time Mg2Si0.53Ge0.47 pn-junction photodiode by thermal diffusion of a thin Ag layer into n-Mg2Si0.53Ge0.47 substrate. The fabricated diode had an obvious rectification behavior and demonstrated a clear zero-biased photoresponse in the wavelength range from 0.95 to 1.85 μm, indicating its prominence for IR sensation in that wavelength domain.
关键词： IR sensation,photoresponse,pn-junction diode,Mg2Si0.53Ge0.47,single crystal
更新于2025-09-10 09:29:36
-
Growth of pure and BFO doped KCl crystals by Czochralski technique and fabrication of microstrip patch antenna for GHz applications
摘要： Large sized pure and 0.1 mol% BiFeO3 (BFO) doped KCl single crystals were grown by Czochralski technique. Structural parameters were confirmed by powder XRD and single crystal XRD. EDX analysis was used to determine the elemental composition of BFO and KCl crystal. Photoluminescence confirmed that BFO acts as defect quenching agent for KCl single crystal which improved its optical transparency. Doping of BFO in KCl single crystal increased its hardness as measured by a Vicker’s microhardness test. The effect of BFO on dielectric constant and dielectric loss of KCl crystal, at various temperature and frequencies was studied. The low dielectric constant viz. 4.5 and 5.8 for pure and BFO doped KCl was helpful in designing and fabricating patch antenna in GHz frequency. As a result of BFO doping, the resonant frequency of microstrip patch antenna can be tuned at 5.40 GHz from 6.01 GHz for the KCl single crystal.
关键词： Czochralski technique,GHz applications,microstrip patch antenna,BiFeO3 (BFO),KCl single crystal
更新于2025-09-10 09:29:36
-
Spectroscopic properties and martensitic phase transition of Y4Al2O9:Ce single crystals under high pressure
摘要： High pressure studies of monoclinic yttrium aluminum oxide single crystals (Y4Al2O9 -YAM) doped with Ce3+ ions grown by micro-pulling-down method are reported. The results of absorption measurements in the mid-infrared prove the existence of four different sites in which Ce3+ ions substitute Y ions, in accordance with the crystallographic structure of YAM. The lowest 5d level of Ce3+ is located very close to the bottom of the conduction band for two of four Ce3+ related centers at ambient pressure, which results in strong temperature quenching of their luminescence. Two other Ce3+ centers do not emit at ambient pressure since their 5d levels are resonant with the conduction band. Application of high pressure above 11 GPa restores their luminescence. Consequences of such energy structure of various Ce3+ sites in YAM for the Dorenbos theory are discussed. The bandgap energy of YAM is found to be 5.93 eV, which is the smallest out of the three yttrium aluminum oxides. High-pressure synchrotron angle dispersive x-ray diffraction and Raman scattering measurements identify a phase transition occurring at pressures between 8 and 11 GPa, which has martensitic character. The second phase transition to another structure (likely with hexagonal symmetry) occurs at a pressure around 16 GPa.
关键词： high pressure,phase transition,X-ray diffraction,luminescence,single crystal
更新于2025-09-10 09:29:36