As-grown Crystals Research Articles

Growth and Nonlinear Optical Properties of GdAl3(BO3)4 in a Flux without Molybdate

Single crystals of the nonlinear optical (NLO) material GdAl3(BO3)4 (GdAB) were successfully grown by top-seeded solution growth method in the new flux Al2O3–B2O3–Li2O–NaF. The ultraviolet (UV) cutoff wavelength of GdAB grown from this new flux is approximately 175 nm, which is shorter than 266 nm. Measurement of second-harmonic generation powder suggested that the effect of the as-grown GdAB crystal is 3.5 times greater than that of KDP (KH2PO4), which was unchanged as the crystal grew from a molybdate-based flux. Therefore, the GdAB crystal obtained from the new flux is a promising candidate for NLO materials, which can be used to achieve fourth-harmonic generation in the UV region.

Improving characteristic of Faraday effect based on the Tm3+ doped terbium gallium garnet single crystal

Highly transparent Tm3+ doped terbium gallium garnet single crystal was grown by the Czochralski(Cz) method for magneto-optical applications. The single-crystal X-ray diffraction confirms that the compound crystallize in the cubic systems with the structure a = b = c = 1.2338 nm. The temperature dependence of the magnetic susceptibility indicates that the Tm:TGG crystal exhibits paramagnetic behavior over the experimental temperature-range 10–300 K. Transmittance spectra and the Faraday rotation have been investigated, which demonstrates that the as-grown crystal shows a high visible transparency and yields a lager Faraday rotation comparable to that of TGG crystal. The increasing of the Verdet constant at measured wavelength and high thermal property show the superior characteristics of Tm3+ doped TGG compared to the pure TGG, indicating that it has significant development for magneto-active materials used in Faraday devices at visible and near-infrared regions (VIS-NIR).

Optical analysis for few TMDC materials

The transition metal dichalcogenides possess layered structure of Se-M-Se (M = Nb, Mo, Ta and W) sandwich interact with each other by van der Waal forces and can also provide sites for intercalation. Because of their technological importance, lubricants, catalysts, battery cathodes and electrodes in the photoelectrochemical solar cells, much attention has gone in the studies of growth of these materials in crystalline and nanocrystalline forms. In the present work we report the growth of NbSe2, MoSe2, TaSe2 and WSe2 single crystals and determine the optical bandgap using optical absorption. The optical absorption of as-grown crystals has been measured at room temperature near the fundamental absorption edge. Both direct and indirect transitions are involved in the absorption process. The indirect transition was found to be allowed with two phonons involved in the process. The direct and indirect energy gaps and phonon energies for all crystals have been estimated. The results obtained are discussed in detail.

Quinolinium-based organic electro-optic crystals: Crystal characteristics in solvent mixtures and optical properties in the terahertz range

We investigate crystal characteristics of ionic organic π-conjugated crystals based on 4-hydroxy-3-methoxystyryl quinolinium (HMQ), which are recently developed acentric crystals showing a large nonlinear optical response and a high THz generation efficiency. Among a few of HMQ derivatives, HMQ-T crystal consisting of the HMQ cation and the 4-methylbenzenesulfonate anion, is chosen for the investigation of solubility, morphology and crystal growth characteristics including optical properties in various single solvents and solvent mixtures. Compared to the solvent mixture of non-aromatic methanol and acetonitrile, HMQ-T crystals in a solvent mixture containing an aromatic solvent (methanol/toluene mixture) exhibits a similar solubility variation with the solvent composition ratio, but based on distinguishable intermolecular interactions with solvent molecules. In addition, solvent mixtures containing an aromatic solvent show a significantly different equilibrium between benzenoid and quinoid forms of the HMQ cation. In contrast to the strong influence of solvent characteristics on solubility behavior, the investigated solvent systems only slightly influence the crystal morphology. Large HMQ-T single crystals with size up to 37 × 6 × 2 mm3 are grown by slow cooling method. We also determine the refractive index and absorption of as-grown single HMQ-T crystals in the broad THz frequency range of 0.3–10 THz.

The role of materials science in the evolution of microelectronics

Abstract

Identification of native defects (vacancies and antisites) in CdSiP2 crystals

Electron paramagnetic resonance (EPR) is used to identify four native defects in single crystals of CdSiP2. This nonlinear optical material is used in optical parametric oscillators to generate tunable output in the mid-infrared. The performance of these frequency-conversion devices is limited when infrared absorption bands associated with native defects overlap a pump wavelength. Cadmium, silicon, and phosphorus vacancies and also silicon-on-cadmium antisites are present in the as-grown undoped CdSiP2 crystals. Using near-band-edge 632.8 nm light from a He-Ne laser, a paramagnetic charge state, and thus an EPR spectrum, is formed at liquid-helium temperatures for three of the four defects. The EPR spectrum from the singly ionized silicon vacancy (VSi−) is present without light and has five hyperfine lines due to equal interactions with the four neighboring 31P nuclei. In contrast, the photoinduced EPR spectrum from the singly ionized cadmium vacancy (VCd−) has a three-line hyperfine pattern due to equal interactions with only two of its four neighboring 31P nuclei. The light-induced spectrum from the singly ionized silicon-on-cadmium antisite (Si Cd+) also has a three-line hyperfine pattern, thus indicating that the unpaired spin interacts primarily with only two 31P neighbors. For the neutral phosphorus vacancy (VP 0), the unpaired spin is primarily localized on the nearest-neighbor silicon ions and the photoinduced EPR spectrum has no resolved 31P hyperfine interactions. The silicon and cadmium vacancies are acceptors, and the silicon-on-cadmium antisite and the phosphorus vacancy are donors.

Synthesis, growth, and structural, optical, mechanical, electrical properties of a new inorganic nonlinear optical crystal: Sodium manganese tetrachloride (SMTC)

A new inorganic nonlinear optical single crystal of sodium manganese tetrachloride (SMTC) has been successfully grown from aqueous solution using the slow evaporation technique at room temperature. The crystals obtained using the aforementioned method were characterized using different techniques. The crystalline nature of the as-grown crystal of SMTC was analyzed using powder X-ray diffraction. Single-crystal X-ray diffraction revealed that the crystal belongs to an orthorhombic system with non-centrosymmetric space group Pbam. The optical transmission study of the SMTC crystal revealed high transmittance in the entire UV–vis region, and the lower cut-off wavelength was determined to be 240nm. The mechanical strength of the as-grown crystal was estimated using the Vickers microhardness test. The second harmonic generation (SHG) efficiency of the crystal was measured using Kurtz's powder technique, which indicated that the crystal has a nonlinear optical (NLO) efficiency that is 1.32 times greater than that of KDP. The dielectric constant and dielectric loss of the compound were measured at different temperatures with varying frequencies. The photoconductivity study confirmed that the title compound possesses a negative photoconducting nature. The growth mechanism and surface features of the as-grown crystals were investigated using chemical etching analysis.

Differential Thermal Analysis and Crystal Growth of CdSiP2

Abstract Thermal properties of CdSiP2 polycrystalline were studied by differential thermal analysis (DTA) technique with a quartz capillary column. It is found that the melting point and crystallization temperature of CdSiP2 are 1139 and 1126 °C, respectively, and the supercooling degree of CdSiP2 melt is evaluated to be 13 °C. According to the results of DTA, the structure of a furnace and the temperature profile of the crystal growth for CdSiP2 were optimized. A crack-free CdSiP2 crystal with 15 mm in diameter and 40 mm in length was grown by the modified vertical Bridgman (VB) method. The X-ray diffractionmeter (XRD), X-ray energy dispersive microanalysis (EDX) and infrared spectrophotometer (IR) were employed to characterize the properties of as-grown crystal. A new cleavage face of (112) was identified in XRD spectrum. The results of EDX indicate that the crystal is of good stoichiometry. The infrared transmission is up to 55% in the infrared region from 7000 to 1500 cm−1. All the characterization results show that the obtained crystal is integrated in structure and good in optical quality which can be used in devices fabrication.

Crystal growth of Ru-doped congruent LiNbO3and investigation of crystalline perfection and optical properties

Single crystals of undoped and Ru-doped congruent LiNbO3(LN) were successfully grown by the Czochralski method. The axial and radial gradient of the radio frequency furnace was controlled in order to obtain crack-free single crystals. Wafers were cut from the grown Ru-doped single crystal at different axial positions along the growth direction and subjected to various characterization analyses. Good optical homogeneity and low residual strain in the grown crystal is confirmed by the conoscopy patterns. Further, it is confirmed that Ru doping does not influence the optical sign of the crystal. From a high-resolution X-ray diffractometry analysis, it is evident that the as-grown undoped LN crystal exhibited better crystalline perfection with a single and sharp diffraction curve in comparison to the Ru-doped crystals, which are characterized by a broader diffraction curve. Absorption coefficient and band-gap analysis across the axial length revealed a concentration variation of Ru across the length. Refractive index measurements carried out using a prism coupler showed variation in the optical birefringence, also due to the variation of Ru concentration at different positions of the grown single crystal.

Faraday effect improvement by Dy3+-doping of terbium gallium garnet single crystal

Highly transparent Dy3+-doped terbium gallium garnet (TGG) single crystal was grown by Czochralski (Cz) method. Phase composition of the crystal was tested by XRD measurements. The distribution coefficient of Dy3+ in the crystal was obtained. The optical and magneto-optical properties were analyzed in detail, and magnetic properties of the Dy3+-TGG crystal were studied. The paramagnetic behavior is observed down to 10K. The as-grown crystal exhibited high optical transmittance, particularly in the visible region. The Faraday rotation was investigated over visible and near-infrared regions (VIS–NIR) at room temperature. The Verdet constants increase at measured wavelengths and high thermal stability was found in Dy3+-doped TGG, as compared to the properties of pure TGG, indicating that Dy3+-doped crystals are preferable for magneto-active materials used in Faraday devices at VIS–NIR wavelengths.

Investigations of thermoluminescence properties of multicrystalline LiF: Mg, Cu, Si phosphor prepared by edge defined film fed growth technique

Thermoluminescence (TL) properties of LiF: Mg, Cu, Si phosphor prepared in multicrystalline form using edge defined film fed growth (EFG) technique has been investigated. The effect of preparation route on TL properties and thermal stability has been studied. To improve the TL dosimetry properties, phosphor is subjected to different annealing temperatures ranging from 250 °C to 450 °C. The shape of the glow curve structure and peak temperature remains similar at different annealing temperatures, however peak intensities vary. The consistency in the glow curve structure with annealing temperature elucidate that TL trapping states are stable in nature. Thermal annealing at 300 °C for 10 min gives maximum TL intensity with main dosimetry peak at 209 °C. The TL intensity of the main dosimetry peak is increased by a factor of five as compared to as-grown crystal. The thermal stability of LiF: Mg, Cu, Si is found to be better than LiF: Mg, Cu, P. Trapping parameters are calculated to have an insight study of defect states. A simple glow curve structure, tissue equivalency, thermal stability, low residual signal, linear response and reusability makes LiF: Mg, Cu, Si a suitable phosphor for radiation therapy, radio diagnostics and personnel dosimetry applications.

Controlled growth of large β-BaB2O4crystals based on theoretical guidelines

The diagram of phase equilibria in the BaB2O4–NaF system has been used to deduce the relationship between the cooling speed (ΔT), the pulling speed (v), the crystal radius (Rs), the slope of liquidus (m), the solution component (x) and the total quantity of melt, namely ΔT= 0.00159Rs2vmx2/G. The theoretical curves of the crystal thickness dependence on cooling rate and pulling rate have also been drawn. Under the guidance of the deduced formulas, the controlled growth of β-BaB2O4(BBO) crystals to a desired size has been achieved. A typical as-grown BBO crystal with dimensions of Ø76 × 33 mm (525.25 g) has been grown successfully by using the high-temperature top-seeded solution growth method. The measured optical homogeneity indicates that the as-grown BBO crystal has high optical quality (Δn≃ 6.9 × 10−6). The experimental curves of the crystal thicknessversusthe cooling rate and pulling rate were in line with the theoretical curves. The phenomenon of diameter shrinkage in the crystal growth has also been explained according to theory and practice. The theoretical derivation and experimental results provide the rationale for further growth of large BBO crystals with high optical quality.

Defect Formation of Nickel-Incorporated Large-Diameter Czochralski-Grown Silicon and Their Effect on Gate Oxide Reliability

Nickel, the related defect distribution of as-grown nickel-incorporated p-type Czochralski-grown silicon crystals, and its effect on the gate oxide reliability were investigated with respect to the boron doping concentration. The segregation of nickel at the surface was more likely in the doping range of 5.5–7.4 × 1014 cm−3 than in the doping range of 1.1–1.7 × 1015 cm−3, which was due to the active formation of Ni–B pairs in the crystal with a higher boron doping concentration. The formation of surface defects was affected by the atomic nickel distribution; that is, the surface defect density was relatively high in the crystal with a lower boron doping concentration. The gate-oxide reliability was aggravated by nickel-related defects, but this effect was noticeably suppressed in the crystal with a higher boron doping concentration. From the breakdown yield and measured laser scattering tomographic defect density, we found the “transferred portion” of bulk nickel defects that causes a degradation in the gate-oxide reliability.

Itinerant antiferromagnetism inFeMnP0.8Si0.2single crystals

Compounds based on the Fe2P structure have continued to attract interest because of the interplay between itinerant and localized magnetism in a non-centrosymmetric crystal structure, and because of the recent developments of these materials for magnetocaloric applications. Here we report the growth and characterization of mm size single crystals of FeMnP0.8Si0.2. Single crystal x-ray diffraction, magnetization, resistivity, Hall and heat capacity data are reported. Surprisingly, the crystals exhibit itinerant antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in the magnetization curves and with the spins ordered primarily in the ab plane. The room temperature resistivity is close to the Ioffe-Regel limit for a metal. Single crystal x-ray diffraction indicates a strong preference for Mn to occupy the larger pyramidal 3g site. The cation site preference in the as-grown crystals and the antiferromagnetism are not changed after high temperature anneals and a rapid quench to room temperature.

Synthesis and magnetic properties of SmOOH crystals

Samarium oxyhydroxide (SmOOH) crystals were synthesized using a flux method. The as-grown crystals were yellowish, transparent, and elongated with a maximum length of approximately 1.0mm. SmOOH adopts a monoclinic structure in the space group P21/m with a=0.4356nm, b=0.3766nm, c=0.6139nm, and β=108.464°. The magnetic susceptibility of the SmOOH crystals exhibited typical Van Vleck paramagnetism, and the experimental data at temperatures above 200K were in close agreement with the calculated results using a spin-orbit coupling constant λ=443K (308cm−1).

Stress-Induced Thermoelastic Martensitic Transformations and Functional Properties in [011]-oriented NiTiHfPd Single Crystals

The stress-induced martensitic transformation in the [011]-oriented Ni45.3Ti29.7Hf20Pd5 (at. %) single crystals in as-grown, homogenized and aged states were investigated in compression. It is experimentally shown that heat treatments of single crystals result in increase in martensitic transformation temperatures, two-fold decrease in reversible strain and increase in strain-hardening coefficient. As-grown single crystals demonstrate large temperature range of superelasticity (up to 140 K), large reversible strain (up to 4.3%) and large work output in comparison with homogenized and aged crystals.

Stress-induced martensitic transformation in high-strength [236]-oriented Ni51Ti36.5Hf12.5 single crystals

The effects of heat treatment on the stress-induced B2-B19' martensitic transformations in the Ni51.0Ti36.5Hf12.5 single crystals oriented along [236] direction are studied. It is shown that in the annealed at 1323K for 4 h crystals, the temperature range of superelasticity increase almost twofold from 75K up to 135K as compared to the as-grown single crystal contained disperse particles of H-phase. The [236]-oriented Ni51.0Ti36.5Hf12.5 single crystals are characterized with high levels of applied compressive stress up to 1700 MPa in the as-grown state and 1900 MPa in annealed crystals for the completely reversible stress- induced B2-B19' martensitic transformation with reversible strain up to |εSE| =1.4%.

Crystal Growth of Ca₃Nb(Ga1-xAlx)₃Si₂O14 Piezoelectric Single Crystals with Various Al Concentrations.

Ca3Nb(Ga1−xAlx)3Si2O14 (CNGAS) single crystals with various Al concentrations were grown by a micro-pulling-down (µ-PD) method and their crystal structures, chemical compositions, crystallinities were investigated. CNGAS crystals with x = 0.2, 0.4 and 0.6 indicated a single phase of langasite-type structure without any secondary phases. In contrast, the crystals with x = 0.8 and 1 included some secondary phases in addition to the langasite-type phase. Lattice parameters, a- and c-axes lengths, of the langasite-type phase systematically decreased with an increase of Al concentration. The results of chemical composition analysis revealed that the actual Al concentrations in as-grown crystals were almost consistent with the nominal compositions. In addition, there was no large segregation of each cation along the growth direction.

Large single crystal growth, transport property, and spectroscopic characterizations of three-dimensional Dirac semimetal Cd3As2.

The three dimensional (3D) Dirac semimetal is a new quantum state of matter that has attracted much attention recently in physics and material science. Here, we report on the growth of large plate-like single crystals of Cd3As2 in two major orientations by a self-selecting vapor growth (SSVG) method, and the optimum growth conditions have been experimentally determined. The crystalline imperfections and electrical properties of the crystals were examined with transmission electron microscopy (TEM), scanning tunneling microscopy (STM), and transport property measurements. This SSVG method makes it possible to control the as-grown crystal compositions with excess Cd or As leading to mobilities near 5–105 cm2V−1s−1. Zn-doping can effectively reduce the carrier density to reach the maximum residual resistivity ratio (RRRρ300K/ρ5K) of 7.6. A vacuum-cleaved single crystal has been investigated using angle-resolved photoemission spectroscopy (ARPES) to reveal a single Dirac cone near the center of the surface Brillouin zone with a binding energy of approximately 200 meV.

Terahertz Radiation Imaging of Ferroelectric Domain Topography in Room-Temperature Hydrogen-Bonded Supramolecular Ferroelectrics

We report quasi-three-dimensional imaging of the ferroelectric domains in a hydrogen-bonded supramolecular ferroelectric 1:1 salt of 5,5′-dimethyl-2,2′-bipyridine and deuterated iodanilic acid by mapping out terahertz waves radiated from the crystal upon femtosecond laser irradiation. Polarization dependence of the effective depth radiating the terahertz waves due to the absorption anisotropy for terahertz waves allows us to distinguish domains in the inside and surface regions of the crystals. In an as-grown crystal, a large domain covering almost all the area is discerned in the inside region, while multidomains are discerned in the surface regions. We observed polarization switching via domain boundary motion in the direction perpendicular to the direction of hydrogen-bonded chains in the surface regions under an external electric field. Obtained images suggest that an uncharged 180° domain wall (DW) parallel to the stacking plane of hydrogen-bonded chains covers the whole area at coercive fields. We a...