Growth Of Large-size Single Crystals Research Articles

Design and Optimization of Thermal Field for PVT Method 8-Inch SiC Crystal Growth.

As a wide bandgap semiconductor material, silicon carbide has promising prospects for application. However, its commercial production size is currently 6 inches, and the difficulty in preparing larger single crystals increases exponentially with size increasing. Large-size single crystal growth is faced with the enormous problem of radial growth conditions deteriorating. Based on simulation tools, the physical field of 8-inch crystal growth is modeled and studied. By introducing the design of the seed cavity, the radial temperature difference in the seed crystal surface is reduced by 88% from 93 K of a basic scheme to 11 K, and the thermal field conditions with uniform radial temperature and moderate temperature gradient are obtained. Meanwhile, the effects of different processing conditions and relative positions of key structures on the surface temperature and axial temperature gradients of the seed crystals are analyzed in terms of new thermal field design, including induction power, frequency, diameter and height of coils, the distance between raw materials and the seed crystal. Meanwhiles, better process conditions and relative positions under experimental conditions are obtained. Based on the optimized conditions, the thermal field verification under seedless conditions is carried out, discovering that the single crystal deposition rate is 90% of that of polycrystalline deposition under the experimental conditions. Meanwhile, an 8-inch polycrystalline with 9.6 mm uniform deposition was successfully obtained after 120 h crystal growth, whose convexity is reduced from 13 mm to 6.4 mm compared with the original scheme. The results indicate that the optimized conditions can be used for single-crystal growth.

Photophysics of β-Ga2O3: Phonon polaritons, exciton polaritons, free-carrier absorption, and band-edge absorption

Monoclinic gallium oxide (β-Ga2O3) has attracted much attention from the fields of optoelectronic and electronic devices owing to the properties of wide bandgap, great breakdown field strength, as well as the economic advantages of low-cost growth of large-size single crystals. Here, the basic photophysical properties including absorption (free-carrier absorption and band-edge absorption) and reflection (phonon polaritons and exciton polaritons) of differently doped β-Ga2O3 with diverse carrier concentrations are studied in detail. The unpolarized reflection spectra of differently doped β-Ga2O3 crystals are well fitted based on the non-polarized reflection model. Besides, according to analysis, the longitudinal–transverse splitting energy of β-Ga2O3 direct excitons is estimated to be as high as 100 meV, reflecting the strong interaction between light and excitons. It is hoped that this work can provide beneficial reference for a comprehensive understanding on the spectral physical characteristics of β-Ga2O3, so as to deepen and expand the basic recognition of this material in the aspect of photophysical properties.

A large size single crystal growth, scientific evaluation, and giant Faraday effect of cadmium manganese telluride

The growth of large-sized Cd0.9Mn0.1T: V ingot was performed using the Te solution vertical Bridgman method. The ingot was cut into wafers and marked for scientific evaluation and property analysis. Through infrared microscopic analysis, we observed the planar growth interface for the first time, and the X-ray diffraction analyses indicated that the crystal possessed excellent crystallinity. Electron probe microanalysis revealed the homogeneous distribution of Mn, Cd, and Te not only in axial, but in radial direction. Inductively Coupled Plasma Mass Spectrometer investigated the distribution rules of various impurities in the axial direction. Te inclusions investigations showed the smaller sizes and the lower densities than previous studies, and the Infrared transmittance was almost up to the theoretical value 63%. These tests have confirmed that the grown crystals are perfect and can be used for device fabrication. The giant Faraday rotation of monochromatic polarized light was generated in the band edge because of the great contributions of the interband exciton transitions. Based on the Faraday effect, the 780 nm optical isolator was fabricated.

Three-Dimensional CA-LBM Numerical Model and Experimental Verification of Cs2AgBiBr6 Perovskite Single Crystals Grown by Solution Method

A three-dimensional cellular automata-lattice Boltzmann (CA-LBM) coupling model is established to simulate the facet growth process and the controlled cooling growth process of Cs2AgBiBr6 perovskite single crystals. In this model, the LBM method is used to calculate the real-time solute field, the CA method is used to simulate the crystal growth process driven by supersaturation of solute, and the geometric parameter g related to the adjacent grid is introduced to reduce the influence of grid anisotropy. The verification of the model is achieved by comparing the simulation results with the experimental results. The comparison results show that a smaller cooling rate is helpful for the growth of large-size single crystals, which verifies the rationality and correctness of the model.

Spin-Coated CH₃NH₃PbBr₃ Film Consisting of Micron-Scale Single Crystals Assisted with a Benzophenone Crystallizing Agent and Its Application in Perovskite Light-Emitting Diodes.

Owing to the superior properties of optical and electronic properties, perovskite single crystals have been in high demand recently. However, the growth of large-sized single crystals requires several processing steps and a long growth time, which engenders great difficulties in device integration. Herein, benzophenone (BP) was firstly introduced as a crystallizing agent to facilitate the construction of a high-quality CH3NH3PbBr3 (MAPbBr3) film consisting of micron-scale single crystals in a one-step spin-coating method. We studied the influence of the BP concentration upon the size and shape of the micron-scale single crystals. Moreover, due to the enhanced morphology of the MAPbBr3 film with low-defect micron-scale single crystals, perovskite light-emitting diodes (PeLEDs) have been demonstrated with a maximum luminance of 1057.6 cd/m2 and a turn-on voltage as low as 2.25 V. This approach not only proposes a concise and highly repeatable method for the formation of micron-scale perovskite single crystals, but also paves a way for the realization of efficient PeLEDs.

Crystal growth and magnetic properties of a kagomé compound Cs2NaMn3F12

Cs2NaMn3F12, one of manganese based fluorides A2A′Mn3F12 (A=Rb, Cs; A′=Li, Na, K), has been found to exhibit a typical kagomé structure. Here, we report the first successful growth of large-sized single crystals of Cs2NaMn3F12 by means of a hydrothermal method. Good quality of grown crystals is confirmed by the XRD and EDS techniques. Magnetic measurements suggest that Cs2NaMn3F12 possesses an antiferromagnetic ordering at 2.5K and a remarkably geometrical frustration effect in the system.

Crystal Growth and Design of Sapphire: Experimental and Calculation Studies of Anisotropic Crystal Growth upon Pulling Directions

The anisotropic growth of large-size sapphire single crystals along different pulling directions was studied on the basis of the chemical bonding theory of single crystal growth and practical Czochralski growth. The projection of thermodynamic morphology of sapphire single crystal respectively along [210], [110], [001], and [001] rotated 57.62° directions can be used to confirm the growth directions of surfaces that are preferred to be exposed thermodynamically in Czochralski growth. Starting from these thermodynamically preferred directions, the possible radial directions that are normal to the four typical pulling directions by kinetic controls have been identified by anisotropic chemical bonding distributions of sapphire single crystal. Chemical bonding calculations demonstrate that the lower pulling rate should be designed when Raxial/Rradial > 1, whereas the higher pulling rate should be designed when Raxial/Rradial < 1. The anisotropic chemical bonding conditions demonstrate the lowest chemical bonding density along the radial directions of sapphire single crystal when it grows along the [001] pulling direction. Taking [001] as the pulling direction in practical growth, a ϕ 2″ sapphire single crystal was grown via the Czochralski method with a growth rate of 2–3 mm/h. Our present work shows the effect of anisotropy on the Czochralski growth of large-size single crystals, which can provide a theoretical guide in practical growth from both thermodynamic and kinetic viewpoints.

Large size single crystal growth of Lu3Al5O12:Pr and their uniformity of scintillation properties

Pr-doped Lu3Al5O12 (Pr:LuAG) single crystals were grown by the Czochralski method. The crystal was seeded-grown in the [100] direction. Dimensions up to 100mm in length and 92mm in diameter were achieved without cracking. Using 10×10×10mm size sample coupled with photomultiplier (Hamamatsu R3998), energy resolution of 4.6% at 662keV was achieved. Uniformity of light yield and energy resolution was also evaluated in whole crystal. The deviations of light output, energy resolution, and decay time were ±7.9%, 7.2%, and 4.8%, respectively.

The development and performance of UV-enhanced APD-arrays for high resolution PET imaging coupled with pixelized Pr:LuAG crystal

The development of high-resolution, UV-enhanced avalanche photodiode (APD) arrays usable in high-resolution PET imaging is underway. These APD arrays were specifically designed as photosensors capable of direct coupling with pixelized Pr-doped Lu 3Al 5O 12 (Pr:LuAG) scintillators. An excellent quantum efficiency (QE) of 55% was achieved at the peak emission of Pr:LuAG (310 nm), namely, a substantial improvement from the QE ≤ 5 % as measured with the conventional Hamamatsu reverse-type APDs (S8664 series). Each APD device has 8×8 (TYP1) and 12×12 (TYP2) pixel structures with active areas of 3×3 mm 2 and 2×2 mm 2 in each pixel, respectively. A gain uniformity of ±8% and low dark noise of ≤ 2 nA / pixel have been achieved, measured at +25 °C. We also report on the large size single crystal growth of improved Pr:LuAG scintillators and the preliminary performance test of the same. An energy resolution of 4.2% (FWHM) was obtained for 662 keV gamma-rays for 10×10×10 mm 3 crystal, measured with a PMT employing a super-bialkali photocathode. We made a test module consisting of a UV-enhanced APD-array (either TYP1 or TYP2) optically coupled with an 8×8 (or 12×12) pixel Pr:LuAG matrix. The linearity between the output signals and incident gamma-ray energy of TYP1 and TYP2 gamma-ray detectors were only 0.27 and 0.33%, as measured at +25 °C for various gamma-ray sources, respectively. Energy resolutions of 7.0±0.2% (FWHM) and 9.0±0.6% (FWHM) were, respectively, obtained for TYP1 and TYP2 detector arrays for 662 keV gamma-rays. The uniformity of the pulse height distributions was also measured at less than 8% for both detectors. Finally, we measured the coincidence timing resolution of these gamma-ray detectors and obtained 4.0±0.1 ns (FWHM) for the 511 keV annihilation quanta from a 22Na source. These results suggest that UV-enhanced APD-arrays coupled with Pr:LuAG scintillators could be a promising device for future application in nuclear medicine.

UHV reactive sputtering of AlN(0001) single crystals on Si(111) at high temperature by a two-step growth method

The growth of large-size single crystals of aluminium nitride has been obtained by UHV reactive rf-sputtering at high temperature (1050 °C). The growth mode was studied in situ by electron spectroscopy (HREELS, LEED) and by ex-situ High Resolution Transmission Electron Microscopy (HRTEM). The deposition of a buffer layer at lower temperature (700 °C) yielded a thick mosaic layer with a very low surface roughness. Electron microscopy has evidenced the presence of a thin interfacial layer composed of small and slightly misoriented domains, suggesting therefore a 3-D growth of the layer before the temperature transition; it has also confirmed the very good crystalline quality of the final thick film: the constituent domains of the film are large (100 nm) and their respective misorientation is less than 0.1 degree.

Nucleation kinetic study of KTiOPO 4 crystallizing from high temperature solution

High temperature solution growth is an important method to grow single crystals of the NLO material KTiOPO 4. K 6P 4O 13 is amongst the best available flux for this purpose. A knowledge of the key parameters such as interfacial tension and metastable zone width will be helpful for the successful growthof large size single crystals. In the present work, the value of the interfacial tension between solid KTP and molten solution was calculated from the knowledge of the solubility data. The metastable zone width was calculated by applying the classical nucleation theory. A comparative study of the different fluxes available for the growth of KTP is made.

Growth of large-size single crystals from fusion

Growth of large-size single crystals from fusion