Bridgman Method Research Articles

Ag+/Bi3+ doping induced band structure and optoelectronic properties changes in CsPbBr3 crystals

Controllable doping is extensively used in designing the electronic and optical properties of perovskite. Bi-doped CsPbBr3 crystal shows a significant redshift at the absorption edge. However, the increase of defect states caused by Bi3+ ions will degrade the optical and electrical properties of the crystal. In this work, we report a series of Ag+/Bi3+ co-doped CsPbBr3 crystals prepared via a Bridgman method. The introduction of Ag+ ions could prevent the change for Fermi level and reduce the concentration of defect states caused by Bi3+ doping. Ag+/Bi3+ co-doped CsPbBr3 crystals show high carrier mobility that compare with undoped CsPbBr3 crystals. The light doping of Ag+/Bi3+ could remarkably improve the detection performances of CsPbBr3 to UV and laser. The maximum photocurrent for Ag+/Bi3+ co-doped CsPbBr3 crystal is even 50 times higher compared with undoped CsPbBr3 crystal under 365 nm UV lamps. Our findings provide a new strategy for controlling doping to improve the photoelectric properties of perovskite.

Growth and scintillation properties of LiBr/CeBr3 eutectic scintillator for neutron detection

A 6LiBr/CeBr3 eutectic thermal-neutron scintillator, with a high 6Li concentration, was developed using the vertical Bridgman method. The grown eutectic contained an 6Li molar ratio of 35%, which is higher than those of the commercial neutron scintillators such as Ce:LiCaAlF6 and Ce:Cs2LiYCl6. Furthermore, it showed optical transparency and a lamellar eutectic structure elongating along the growth direction. The synthesized eutectic showed emission peaks at 360 and 380 nm, originating from the Ce3+ 5d-4f transition in the CeBr3 scintillation phase. The scintillation performance of 6LiBr/CeBr3 was evaluated under X-ray, γ-ray, and neutron irradiation to corroborate its neutron detection potential.

Ultralow Detection Limit and Robust Hard X-ray Imaging Detector Based on Inch-Sized Lead-Free Perovskite Cs3Bi2Br9 Single Crystals.

Halide perovskites are promising candidates for soft X-ray detection (<80 keV) owing to their high X-ray absorption coefficient, resistivity, and mobility lifetime product. However, the lack of large high-quality single crystals (SCs) renders it challenging to manufacture robust hard X-ray imaging systems (>100 keV) with a low detection limit and stable dark current. Herein, high-quality inch-size two-dimensional (2D) Cs3Bi2Br9 (CBB) single crystals are grown from a melt via the Bridgman method. The crystal quality is enhanced by eliminating inclusions of CsBr-rich phases and restraining the trap-state density, leading to an enhanced resistivity of 1.41 × 1012 Ω cm and a mobility lifetime product of 8.32 × 10-4 cm2 V-1. The Au/CBB/Au single-crystal device exhibits a high sensitivity of 1705 μC Gyair-1 cm-2 in all-inorganic bismuth-based perovskites and an ultralow detection limit of 0.58 nGyair s-1 in all of the bismuth-based perovskites for 120 keV hard X-ray detection. The CBB detector exhibits high work stability with an ultralow dark current drift of 2.8 × 10-10 nA cm-1 s-1 V-1 and long-term air environment reliability under a high electric field of 10 000 V cm-1 owing to the ultrahigh ionic activation energy of the 2D structure. The proposed robust imaging system based on CBB SC is a promising tool for X-ray medical imaging and diagnostics.

Large size growth of terbium doped BaCl2/NaCl/KCl eutectic for radiation imaging

In this study, a large-size eutectic scintillator of Tb-doped BaCl2/NaCl/KCl was grown using the Czochralski (Cz) and halide vertical Bridgman methods (H-VB). The suitability of these two growth methods for growing the eutectic was compared. Finally, 1 inch diameter eutectic bulks were obtained using the H-VB method. The Tb3+-derived strongest intensity peak at approximately 550 nm was observed by X-ray irradiation. An approximately 3 × 3 mm transparent eutectic wafer was cut and polished from the grown eutectic bulk. An imaging test using α-ray was performed using the grown eutectic, a fiber optic plate, and an electron-multiplying CCD camera. The resolution performance for radiation-imaging applications was evaluated.

Thermal expansion anisotropy of CuIn11Se17 single crystals

Homogeneous single crystals of CuIn11S17 with 14 mm in diameter and 40 mm in length were grown by directional crystallization of the melt (vertical Bridgman method). The composition and structure of the obtained single crystals were determined by the X-ray microanalysis and the X-ray diffraction analysis, respectively. It is shown that the obtained single crystals crystallize in a hexagonal structure. The anisotropy of thermal expansion was investigated for single crystals oriented parallel and perpendicular to the main crystal axis in the temperature range of 120–600 K. It was found that anomalies of thermal expansion are observed in the indicated single crystals oriented parallel to the main crystal axis.

Growth of a novel K0.4Rb0.6Pb2Cl5 crystal and theoretical and experimental studies of its electronic and optical properties

We report on successful growth by Bridgman method of an optical quality K0.4Rb0.6Pb2Cl5 crystal and determination of its crystal structure and electronic and optical properties. In particular, the present results indicate that the K0.4Rb0.6Pb2Cl5 crystal crystallizes in monoclinic space group P21/c, with the unit-cell parameters as follows: a = 8.9484(2) Å, b = 7.9802(2) Å, c = 12.5359 Å, and β = 90.1220(10)°. For the K0.4Rb0.6Pb2Cl5 crystal, we use X-ray photoelectron spectroscopy (XPS) to measure binding energies of the core-level electrons for constituting atoms and to reveal the energy distribution of the valence electronic states. Our XPS measurements indicate very low hygroscopicity of the K0.4Rb0.6Pb2Cl5 crystal surface and partial alteration from Pb2+ ions to Pb0 when using bombardment with 3 kV Ar + ions. To find peculiarities of filling the valence band and the conduction band of the K0.4Rb0.6Pb2Cl5 crystal by partial densities of electronic states associated with the composing atoms, we apply different approaches for exchange-correlation potential using model K0.5Rb0.5Pb2Cl5 solid solution. We have found that the finest agreement of the experimental and theoretical data is derived when in the calculating procedure we use Tran-Blaha modified Becke-Johnson (TB-mBJ) potential involving spin-orbit coupling and the Hubbard parameter U (TB-mBJ + U + SOC approach). The present theoretical TB-mBJ + U + SOC results predict that K0.5Rb0.5Pb2Cl5 is a non-direct material with energy band gap of 4.167 eV. The optical properties of K0.5Rb0.5Pb2Cl5 are elucidated theoretically in detail based on first-principles calculations within the TB-mBJ + U + SOC model.

Growth and scintillation properties of Ce doped [formula omitted]LiBr/LaBr[formula omitted] eutectic scintillator for neutron detection

In this study, Ce:6LiBr/LaBr3 eutectic with a high Li concentration was developed as a novel thermal neutron scintillator. Ce served as an activator for the LaBr3 phase, and Ce:6LiBr/LaBr3 eutectics were grown via the vertical Bridgman method in quartz ampoules (inner diameter = 4 mm). In the eutectic, the 6LiBr phase worked as the neutron capture phase by the 6Li (n, a) 3H reaction, and Ce:LaBr3 worked as the scintillator phase. The Ce:6LiBr/LaBr3 eutectic exhibited a lamellar eutectic structure and optical transparency, as well as 350 and 380 nm emission due to Ce3+ 5d-4f transition. The light yield under neutrons excitation was estimated to be 74000 photons/neutron. The scintillation decay time was 18.7 ns.

Optimized Bridgman growth and quality improvement of LiInSe2 crystal by annealing in Li2Se vapor atmosphere

Mid-infrared (MIR) lasers based on nonlinear frequency conversion by nonlinear optical (NLO) crystals are urgently desired for various military and civilian applications. LiInSe2 (LISe) crystal has aroused intense attention due to its remarkable optical properties. However, the presence of point defects in LISe increases absorption loss and degrades the laser damage threshold (LDT), which limits the practical application in high-power MIR lasers. Therefore, it is essential to reveal the defect types and their formation mechanism in LISe, which is beneficial to design a rational strategy to improve the crystal quality. Here, large-sized LISe crystals with a diameter of 26 mm were successfully grown by the optimized Bridgman method using oriented seed crystal. Furthermore, three types of defects, VSe, VLi, and InLi in the as-grown LISe crystals were verified by photoluminescence (PL) spectra. Therefore, we designed the thermal annealing process under Li2Se vapor to compensate for the losses of Li and Se elements and reduce the defect concentration in LISe. Moreover, the evolution of defects in LISe crystals was determined by X-ray photoelectron spectroscopy (XPS), PL and ultrafast transient absorption spectra (TAS). All the experimental results confirm that the defect concentration in LISe greatly decreases and the crystal quality was obviously improved after annealing under Li2Se vapor. More importantly, this work provides a general strategy to reveal the defects in crystals and to improve the crystal quality of MIR chalcogenides for practical applications.

Experimental verification of vacancy defects and their vital role on reddish Bi4Ge3O12 single crystals

Reddish bismuth germanate (Bi4Ge3O12, BGO) crystals are found during the industrial large-size and -scale crystal growth by Bridgman method, which directly causes visible absorption. The reddish can be eliminated by a modified oxygen-annealing. Oxygen vacancy is further confirmed through electron paramagnetic resonance, X-ray photoelectron spectroscopy, Raman spectroscopy to demonstrate the existence of vacancy defects and elucidate the nature and role. Bi vacancy in reddish BGO single crystals is verified via scanning transmission electron microscopy, energy-dispersive spectroscopy, and high-angle annular dark-field scanning TEM. The essence of annealing and vacancy evolution is also discussed.

Growth and optical characterization of Sn0.6Sb0.4Se layer single crystals for optoelectronic applications

SnSe compound is an attractive semiconductor material due to its usage in photovoltaic applications. The substitution of Sb in the SnSe compound presents a remarkable advantage especially in point of tuning optical characteristics. The present paper reports the structural and optical properties of Sn1-xSbxSe (x = 0.4) layered single crystals grown by the vertical Bridgman method. To the best of our knowledge, this work is the first investigation of the Sn0.6Sb0.4Se crystal grown with the vertical Bridgman technique. X-ray diffraction (XRD) pattern of the grown crystal indicated the well crystalline structure of the grown crystals. Lattice strain and interplanar spacing of the crystal structure were determined using the XRD pattern. Scanning electron microscope images allowed to the observation of the layer crystal structure. The layer crystalline structure shows 2D material properties and provides 2D applications. Optical properties were revealed by carrying out Raman, ellipsometry and transmission measurements. Raman modes, refractive index, extinction coefficient, and dielectric spectra, band gap energy of the crystal were presented throughout the paper. The obtained results indicated that Sn1-xSbxSe (x = 0.4) layer single crystals may be an alternative potential for photovoltaic and optoelectronic applications.

Abnormal thermal expansion and thermal conductivity of CuIn-=SUB=-7-=/SUB=-Se-=SUB=-11-=/SUB=- single crystals

Homogeneous CuIn7Se11 single crystals with a diameter of ~14 mm and length of ~ 40 mm have been grown from the melt using the Bridgman method. Composition and structure of the obtained single crystals have been defined. It was shown that the obtained single crystals crystallized in a hexagonal structure. The anisotropy of thermal expansion and thermal conductivity in the temperature range of 80-650 K has been investigated on oriented single crystals in parallel and at right angle to the main crystal axis c. Abnormal thermal expansion and thermal conductivity were observed on the single crystals oriented in parallel to the main crystal axis. Keywords: Bridgman method, single crystals, crystalline structure, thermal expansion, thermal conductivity.

Magnetic properties of Pb-=SUB=-1-y-=/SUB=-Sc-=SUB=-y-=/SUB=-Te alloys

The magnetic field dependences of the magnetization (B≤9 T, T=2-70 K) of the samples from a single crystal Pb1-yScyTe (y=0.01) ingot, synthesized by the Bridgman method, are studied. It is established that, in accordance with the generally accepted model of the rearrangement of the electronic structure of alloys during doping, there is no paramagnetic contribution of single scandium ions located in the nodes of the metal sublattice in the studied samples. The magnetization of the samples contains several contributions: superparamagnetism of scandium clusters, linear in field diamagnetism of the crystal lattice and the paramagnetism of free electrons, as well as the oscillating contribution of the de Haas--van Alphen effect. The field dependences of the main contribution of scandium clusters are successfully approximated using the Langevin function. The average concentration, magnetic moment and the total magnetic moment of the clusters per unit volume of the sample were determined with an increase in the impurity concentration along the ingot. Keywords: PbTe-based alloys, 3d-transition metal impurities, rearrangement of electronic structure, field dependences of magnetization, superparamagnetism of scandium clusters.

Growth, crystal structure and temperature dependence of the band gap of Cu-=SUB=-2-=/SUB=-ZnGeS-=SUB=-4-=/SUB=- single crystals

Cu2ZnGeS4 single crystals were grown by chemical vapor transport reaction method. Their composition and crystal structure were determined. It was shown that the obtained single crystals crystallize in a tetragonal structure. The band gap of the obtained single crystals was determined basing on transmission spectrum in the region of the absorption edge in temperature range of 10-320 K. It was found that band gap width increases with decreasing of temperature. Keywords: Bridgman method, single crystals, crystal structure, transmission spectrum, band gap.

Bridgman growth and electrical properties of Nd-doped PMN–PT single crystal with ultrahigh piezoelectricity

The work presents electrical properties of Nd–PMN–PT single crystal grown by Bridgman method. As-grown crystal has been verified to have ultrahigh piezoelectric coefficient d33 with maximum value of 3650 pC N−1 under alternating current polarization.

Growth, spectra and continuous-wave 2.1 μm laser operation of a Ho3+-doped bismuth silicate crystal

A Ho3+:BSO crystal was grown using the Bridgman method. The 2.1 μm CW laser of the crystal was demonstrated.

Impact of Dysprosium doping on the structural and electrical properties of BiSbTe3 single crystals

Breaking of time reversal symmetry in 3D topological insulators and tuning of Fermi level in the vicinity of the Dirac point is a prerequisite for unravelling various exotic physical phenomena which might be leveraged for potential technological device applications. Here we account effective single crystal growth of (BiSb)2-xDyxTe3 where x = 0, 0.005, 0.05 using modified Bridgman method. The structural, morphological, electrical and Hall measurements were performed on the synthesized single crystals. X-ray Diffraction (XRD) measurements confirmed high quality crystal growth with unidirectional orientation of the synthesized crystals. The lattice parameters were found decreasing with Dysprosium (Dy) doping thereby decreasing the lattice volume,indicating the incorporation of Dy atoms in the lattice of BiSbTe3. Scanning Electron Microscopy (SEM) confirmed the layered morphology of synthesized crystals while Energy Dispersive X-ray Spectroscopy (EDX) measurements revealed the uniform distribution of all the elements as well as stoichiometry of prepared crystals. The resistivity versus temperature (ρ-T) plot from 4 K to 300 K showed metallic behaviour of crystals with an increase in resistivity with Dy doping. The Hall resistivity (ρxy) demonstrates that holes are the predominant charge carriers. The Hall data revealed displacement of Fermi level with Dy doping. These results are indicative to the shift in the Fermi level in the vicinity of the Dirac point.

In‐Situ Loading Bridgman Growth of Mg3Bi1.49Sb0.5Te0.01 Bulk Crystals for Thermoelectric Applications

AbstractThe single crystal growth of Mg3Bi2‐based thermoelectric materials is of great significance for their applications near room temperature. So far, it is still a big challenge to grow such bulk single crystals and attempts are primarily focused on the metal flux methods. For the first time, bulk single crystals of n‐type Mg3Bi1.49Sb0.5Te0.01 are directly grown by applying an In‐situ Loading Bridgman method. The as‐grown single crystal features an excellent carrier mobility of 220 cm2 V−1 s−1, which is among the best compared to other Mg3Bi2‐based bulk materials. Besides, this method is successfully developed to fast grow uniform polycrystalline materials with high thermoelectric and mechanic performance. As demonstrated by the single‐leg device, a large temperature difference of 10.5 K is achieved at the supplied electric current of 0.6 A, much superior to other room temperature state‐of‐the‐art thermoelectric materials. With the single crystalline and polycrystalline materials prepared reliably and conveniently, in‐depth investigations on the Mg3Bi2 thermoelectric system can be greatly benefited, which should as well significantly facilitate their practical applications at room temperature.

Growth and scintillation properties of Eu doped Li2SrCl4/LiSr2Cl5 eutectic

In this study, a Eu-doped Li2SrCl4/LiSr2Cl5 eutectic with a high 6Li concentration was developed as a novel thermal neutron scintillator. The doped Eu served as an activator in the Li2SrCl4 and LiSr2Cl5 phases. The Eu-doped Li2SrCl4/LiSr2Cl5 eutectic was grown using the vertical Bridgman method in a sealed quartz ampoule. The eutectic exhibited a lamellar eutectic structure elongated along the pulling direction, and was optically transparent. The emissions at 401 and 412 nm were attributed to the Eu2+ 4f-5d transition in the Li2SrCl4 and LiSr2Cl5 phases, respectively. The light yield under 5.5 MeV α -rays was estimated to be 5,600 photons/5.5 MeV α -rays. The scintillation decay time was 312 ns. In the eutectic, the Li2SrCl4 and LiSr2Cl5 phases contributed to scintillation and neutron capture by the 6Li (n, a) 3H reaction.

Surface-barrier structures based on solid solutions (In &lt;sub&gt;2 &lt;/sub&gt;S &lt;sub&gt;3 &lt;/sub&gt;) &lt;sub&gt;х &lt;/sub&gt;•(AgIn &lt;sub&gt;5 &lt;/sub&gt;S &lt;sub&gt;8 &lt;/sub&gt;) &lt;sub&gt;1–х &lt;/sub&gt;

Single crystals of solid solutions (In2S3)x⋅ (AgIn5S8)1–x were grown by the method of directional crystallization of the melt (Bridgman method). Studies of the elemental composition and crystal structure of these single crystals have been carried out. On the basis of solid solutions (In2S3)x⋅ (AgIn5S8)1–x, photosensitive structures have been created for the first time and the photoelectric properties of these structures have been determined. The possibility of using the created structures as broadband photoconverters of optical radiation is shown.

High piezoelectricity after field cooling AC poling in temperature stable ternary single crystals manufactured by continuous-feeding Bridgman method

After field cooling (FC) alternating current poling (ACP), we investigated the dielectric and piezoelectric properties of [001]pc-oriented 0.24Pb(In1/2Nb1/2)O3 (PIN)-0.46Pb(Mg1/3Nb2/3)O3 (PMN)-0.30PbTiO3 (PT) (PIMN-0.30PT) single crystals (SCs), which were manufactured by continuous-feeding Bridgman (CF BM) within morphotropic phase boundary (MPB) region. By ACP with 4 kVrms/cm from 100 to 70 °C, the PIMN-0.30PT SC attained high dielectric permittivity (ε33T/ε0) of 8330, piezoelectric coefficient (d33) of 2750 pC/N, bar mode electromechanical coupling factor k33 of 0.96 with higher phase change temperature (Tpc) of 103 °C, and high Curie temperature (TC) of 180 °C. These values are the highest ever reported as PIMN-xPT SC system with Tpc > 100 °C. The enhancement of these properties is attributed to the induced low symmetry multi-phase supported by phase analysis. This work indicates that FC ACP is a smart and promising method to enhance piezoelectric properties of relaxor-PT ferroelectric SCs including PIMN-xPT, and provides a route to a wide range of piezoelectric device applications.