Cz Method Research Articles

Investigation of growth and polarized spectra of Ho3+ ions heavily doped BaY2F8 crystal

A BaY2F8 (BYF) single crystal heavily doped with Ho3+ ion was grown successfully using the Czochralski (Cz) method. The infrared fluorescence spectra (2–4 μm) and fluorescence lifetime at 3.9 μm were investigated. The detailed polarization absorption properties of Ho:BYF, especially the absorption spectrum in 850–950 nm range, were reported for the first time. The maximum absorption cross-section was at 888.15 nm, σabs = 1.26✕10−21 cm2 (E//c). In comparison, the peak positions of the absorption cross sections in the other two polarization directions were at 885.80 nm and 890.45 nm, respectively, indicating that incident light's polarization direction greatly influences absorption. The spectroscopic parameters were calculated based on the Judd–Ofelt theory.

Characterization of defects in Tb3Ga5O12 single crystals grown by the Czochralski method

Tb3Ga5O12 (TGG) single crystals, which are used as optical isolators, are grown by the Czochralski (Cz) method. Radial stripes are sometimes observed inside the TGG-grown single crystals. Polarized light microscopy, chemical etching, and X-ray topography results suggest that helical dislocations are present in crystals with radial stripes. Therefore, the radial stripes are considered to be caused by light scattering due to the strain resulting from helical dislocation.

Structure, spectroscopy and LD end-pumped laser performance of an Er,Pr:LuYSGG crystal operated at ∼2.8 μm

We demonstrate the structure, spectroscopy, and laser performance of an Er3+ and Pr3+ co-doped LuYSGG crystal grown by the Cz method.

Czochralski growth, optical and magneto-optical properties of Ce9.33(SiO4)6O2 crystal

Ce9.33(SiO4)6O2 (CSO) crystals were grown by the Czochralski (Cz) method. Rietveld refinement of XRD patterns confirmed the oxyapatite structure of CSO, XPS analysis revealed the valence of Ce ions in CSO crystals. Magnetization curve and temperature dependencies of the magnetic susceptibility were measured, paramagnetic behavior and magnetic anisotropy have been observed. Photoluminescence and Faraday rotation characteristics of the CSO crystal were investigated at room temperature. Verdet constants of CSO were about 1.6 times as large as those of TGG. Baesd on Van Vleck–Hebb theory, the effective transition wavelength and probability of CSO crystal were calculated and compared with other Ce3+-containing crystals. The absorption and magnetic circular dichroism (MCD) spectra of 4f→5d transitions in Ce3+ ions in CSO crystal were studied.

Enhancement of the optical properties of a Dy3+:Sr3Gd2(BO3)4 crystal by Ca2+ co-doping

In this work, polycrystalline Dy3+:(Sr1-xCax)3Gd2(BO3)4 (x = 0–0.9) compounds doped with different concentrations of Ca2+ were synthesized by solid-state reaction. On the basis of their structural and spectral data, the optimal Ca2+ ions doping concentration of 60 at.% was determined. Then the Dy3+:(Sr0.4Ca0.6)3Gd2(BO3)4 crystal was obtained by the Czochralski (Cz) method. The crystal has a relatively high absorption cross-section at 453 nm, which is 0.98 × 10−21 cm2 (E//c) with a full width at half maximum (FWHM) of 9 nm (E//c). The maximum emission cross-section of the 4F9/2 → 6H13/2 transition at 576 nm is 5.62 × 10−21 cm2 (E//c) with a FWHM of 14 nm. The fluorescence quantum efficiency is 52.5 %. Compared with the Dy3+:Sr3Gd2(BO3)4 crystal, the emission cross-section and fluorescence quantum efficiency of the Dy3+:(Sr0.4Ca0.6)3Gd2(BO3)4 crystal have been significantly improved. These further increase the possibility of the crystal emitting a yellow laser.

Scintillation properties of [formula omitted]:[formula omitted] crystals grown by Cz, EFG and Bridgman methods with a multifunctional melt growth furnace

Cs3Cu2I5:Tl is a novel scintillator boasting high density, a substantial light yield, and excellent energy resolution, making it promising for applications in gamma-ray spectroscopy. In this paper, we developed a multi-functional melt growth furnace capable of convenient configuration for the Czochralski (Cz), Edge-defined Film-fed (EFG), and Bridgman methods. We successfully grew Cs3Cu2I5:Tl crystals using the Cz, EFG, and Bridgman methods, yielding crystal sizes of Φ15 mm, Φ12 mm, and Φ30 mm, respectively. The obtained crystals exhibit satisfactory crystalline quality, although they are susceptible to cracks during the cooling, cutting, and polishing processes. Samples are taken from the crystals to undergo analysis to investigate their optical and scintillation properties. Findings indicate that our Cs3Cu2I5:Tl possess a large Stokes shift of 175 nm with nearly no spectral overlap between the PLE and PL spectra. The radioluminescence emission peaked at 505 nm, accompanied by a scintillation decay time of 828 ns. The samples exhibited a commendable energy resolution of 4.8% at 662 KeV and a high light yield of 83000 ph/MeV when coupled with a PMT. This study validates the viability of employing CZ and EFG methods for the growth of Cs3Cu2I5:Tl crystal, in addition to showcasing the Bridgman method for the growth of centimeter-scale Cs3Cu2I5:Tl crystals.

Extended Hypothesis for Reynolds Stress Tensor and Turbulent Heat Flux Modeling Within a Novel K‐ε Model for Prediction of Crystal Growth from the Melt

AbstractThe major technique of manufacturing silicon monocrystals is Czochralski (Cz) method. To obtain high‐quality crystals, it is necessary to control the melt flow that is turbulent. The most cost‐effective approach for modeling turbulence nowadays is RANS (Reynolds Averaged Navier‐Stokes) that allows for providing steady axisymmetric computations using reasonable grids. However, conventional eddy‐viscosity RANS models usually fail to predict spatial details of turbulence characteristics of the melt flow. To overcome the limitations of the eddy‐viscosity approach the Stress Tensor Reconstruction (STR) approach is developed that is aimed at the reproduction of anisotropy of the Reynolds stresses. The Generalized Gradient Diffusion Hypothesis (GGDH) in combination with the STR approach successfully takes into account the anisotropy of turbulent fluxes in a melt flow. Relying upon the STR/GGDH approach a novel RANS STR k‐ε model is developed. The model is validated using the ILES (Implicit Large Eddy Simulation) data of turbulent melt convection during Cz Si crystal growth, as well, as the experimental data of oxygen concentration in 100 and 200 mm diameter Cz crystals. The results are compared to the results obtained with the conventional low Reynolds number Chien k‐ε model extended by the buoyancy generation term.

Insight into the photoluminescence and thermoluminescence properties of Tb ions doping KCl crystal grown by Cz method

Insight into the photoluminescence and thermoluminescence properties of Tb ions doping KCl crystal grown by Cz method

Upconversion luminescence and optical thermometry behaviors of Yb3+ and Ho3+ co-doped GYTO crystal

Optical thermometry based on the upconversion (UC) luminescence intensity ratio (LIR) has attracted considerable attention because of its feasibility for achievement of accurate non-contact temperature measurement. Compared with traditional UC phosphors, optical thermometry based on UC single crystals can achieve faster response and higher sensitivity due to the stability and high thermal conductivity of the single crystals. In this study, a high-quality 5 at% Yb3+ and 1 at% Ho3+ co-doped Gd0.74Y0.2TaO4 single crystal was grown by the Czochralski (Cz) method, and the structure of the as-grown crystal was characterized. Importantly, the UC luminescent properties and optical thermometry behaviors of this crystal were revealed. Under 980 nm wavelength excitation, green and red UC luminescence lines at 550 and 650 nm and corresponding to the 5F4/5S2 → 5I8 and 5F5 → 5I8 transitions of Ho3+, respectively, were observed. The green and red UC emissions involved a two-photon mechanism, as evidenced by the analysis of power-dependent UC emission spectra. The temperature-dependent UC emission spectra were measured in the temperature range of 330–660 K to assess the optical temperature sensing behavior. At 660 K, the maximum relative sensing sensitivity (Sr) was determined to be 0.0037 K−1. These results highlight the significant potential of Yb,Ho:GYTO single crystal for optical temperature sensors.Graphical abstract

Thermal, spectroscopy and optimized ∼3 µm CW laser properties for Ho,Pr:YAP crystal.

We demonstrate the thermal, spectroscopy and laser properties of Ho,Pr doped YAP crystal grown successfully by Cz method. The thermal expansion coefficient, thermal conductivity, absorption and emission spectra of Ho,Pr:YAP crystal are investigated in detail. Additionally, the level lifetimes suggest that Pr3+ is a suitable deactivating ion for Ho:YAP crystal. Particularly, the actual laser performance is optimized by doping active ion Ho with high concentrations and introducing deactivated Pr3+, resulting in decreased laser threshold, increased laser output power and slope efficiency. A 3.01 µm laser with output power of 502 mW, slope efficiency of 6.3% and beam quality factors of 1.42/1.43 is achieved in the Ho,Pr:YAP crystal, as far as we know this is the highest ∼3 µm CW laser power realized in Ho3+ doped oxide crystals.

Crystal growth and infrared-to-visible upconversion luminescence in Nd-Yb-Tm: CaYAlO4 single crystal

Yb3+/Tm3+: CaYAlO4 (CYA) and Nd3+/Yb3+/Tm3+: CYA bulk single crystals were grown using the Czochralski (Cz) method. The polarized absorption, upconversion luminescence (UCL) spectra under 980 nm and 808 nm pumping, and fluorescence decay curves were measured as well as Judd-Ofelt (J-O) theory calculations were performed to investigate the sensitization effect of Yb3+ and Nd3+/Yb3+co-doping in Tm3+: CYA single crystal. Obvious enhancement was observed in Tm3+-activated crystals for the blue upconversion emission (∼474 nm) when doped with Yb3+ or co-doped with Nd3+/Yb3+. The energy transfer efficiency is 72.6% (Yb3+→Tm3+) and 71.7% (Nd3+→Yb3+/Tm3+) in Yb3+/Tm3+: CYA and Nd3+/Yb3+/Tm3+: CYA single crystals respectively. The gain cross-sections were calculated, and it can stated that the blue laser output derived from upconversion is possible around 474 nm related to the transition of 1G4→ 3H6 in Yb3+/Tm3+: CYA and Nd3+/Yb3+/Tm3+: CYA crystals.

Evaluation of numerical simulation of constitutional supercooling during heavily Boron-Doped silicon crystal growth using Cz method

Using the Czochralski (Cz) method, it has been established that heavily doped silicon (Si) single crystals with impurities such as boron (B) can negatively impact the quality of grown crystals due to morphological instabilities such as cellular growth caused by constitutional supercooling for doping higher than 1 × 1019 cm−3. To produce high-quality heavily doped Si single crystals, constitutional supercooling must be prevented during growth. In this study, we used a three-dimensional numerical simulation to predict constitutional supercooling during the growth of heavily B-doped Cz-Si single crystals, considering the transport of B in the melt and the segregation effect. We compared the numerically predicted constitutional supercooling region with experimental data to assess its accuracy and found that the cellular growth region observed in the experiment was in good agreement with the region of constitutional supercooling predicted by the simulation. Moreover, we considered the effects of different pulling rates and crystal lengths during the growth process on constitutional supercooling, and the limitations of numerical modelling.

Czochralski (CZ) process modification with cooling tube in the response to market Global silicon shortage

Recently, the silicon wafer producers, affected by Covid-19 and USA-China competition, looks for new production processes to increase the production. On the other hand, the common parts of CZ puller such as heater, crucible and thermal shield are optimized over time and now the common CZ process is reached to limitation for further improvement. Here, we propose a modified CZ method by adding a cooling tube into the growth zone. The new proposed Cz method is applied to the 8″ crystal growth process. A fully 3D transition model including energy equation, Navier–Stokes equation, surface-to-surface radiation heat transfer, moving mesh and thermal stress equations is implemented. The simulation is performed for both original and new CZ method. It was proved that the new CZ method increases the pulling speed up to 25 %. To ensure about the crystal quality, the thermal stress is compared between original and new proposed CZ method. Although it was found that the thermal stress increases about twice but still the maximum von Mises stress never exceeds the critical value 25 MPa. Additionally, the power consumption is also found to enhance maximum 2 kW under new conditions. To evaluate the model the interface and heater power for the original CZ puller is compared with industrial CZ process and it shows acceptable accuracy.

Impact of Marangoni effect of oxygen on solid–liquid interface shape during Czochralski silicon growth applied with transverse magnetic field

This study investigated the impact of the Marangoni effect of oxygen on the solid–liquid interface shape in the silicon single-crystal growth process by the transverse magnetic-field-applied Czochralski (Cz) method. To this end, the results of a 3D heat and mass transfer analysis were compared with the experimental results. The findings of the study revealed that the Marangoni effect of oxygen affected the solid–liquid interface shape predicted by the simulation. Moreover, with the introduction of this effect, both the solid–liquid interface shape and temperature distribution of the melt were found to be in good agreement with the experimental values.

Numerical simulations considering effects of thermal stress and impurities on the behavior of intrinsic point defects in Si crystal growing by Cz method

Numerical simulations considering effects of thermal stress and impurities on the behavior of intrinsic point defects in Si crystal growing by Cz method

Dy3+ and Tb3+ codoped mixed garnet crystals with a high-disorder structure for promising efficient InGaN laser-diode pumped yellow lasers

Dy3+ and Tb3+ codoped mixed garnet crystals with a high-disorder structure were grown by the Cz method. These mixed crystals exhibit distinct advantages for the development of blue laser diode pumped one-step solid-state yellow lasers.

Exploration of impurity migration behavior in the process of lanthanum purification by Czochralski method

In order to improve the purification efficiency of La, the Czochralski (Cz) method was introduced into the purification of rare earth metal La for the first time in this work. And the migration behavior of Al, Fe and Ni impurity in the process of La purification by Czochralski method was obtained. The equilibrium separation coefficients k0 of Al, Fe and Ni were first calculated by the slope of liquidus. As k0 < 1, Al, Fe and Ni impurities in La will be concentrated in the melt and removed by the Cz method. Then, the effect of pulling speed on the effective separation coefficient keff of Al, Fe and Ni impurities in La was calculated by BPS model, which indicates that with the reduction of the pulling speed, keff of Al, Fe and Ni impurities gradually decreases, and the impurity removal efficiency increases. And by the purification experiments, when the pulling speed is 0.3 mm/min, the residual rates of Al and Fe impurities in La are the lowest, 40 % and 45.65 % respectively; Ni and Ca impurities are reduced below 10 ppm.wt. The purity of La can be increased from 99.97 wt% to more than 99.995 wt% after purification by the Cz method, indicating that the Cz method is an effective method for purification of La.

Crystal growth and optical spectroscopic properties of Ce3+/Dy3+ co-doped CaYAlO4 crystal for yellow laser emission

Nowadays, yellow laser has been attractive worldwide since its various applications. Dysprosium (Dy3+) is one of the most suitable lanthanide ions for directly producing yellow laser emission, but it suffers from low cross-sections and cross-relaxation processes. Herein, the co-doped 0.5% Ce3+/1% Dy3+:CaYAlO4 (CYA) crystal with high optical quality was successfully grown using the Czochralski (Cz) method in a reducing H2/Ar atmosphere. Spectroscopic properties, including polarized absorption, emission cross-sections, and lifetime, were characterized. Ce3+ co-dopant was used as a sensitizer to enhance the fluorescence properties of Dy3+.

Shape-Controlled Crystal Growth of Y3Al5O12:Ce Single Crystals with Application of Micro-Pulling-Down Method and Mo Crucibles, and Their Scintillation Properties

The technology to grow single crystals of the required shape directly from a melt has been researched extensively and developed in various industries and research fields. In this study, a micro-pulling-down method and a Mo crucible were applied to the shape-controlled crystal growth of Y3Al5O12:Ce (YAG:Ce). Three types of Mo crucibles with different die shapes were developed. Stable crystal growth of more than 50 mm in length was achieved with the same shape as the die, and scintillation light output of ~20,000 ph/MeV, which is comparable with those of the YAG:Ce crystal grown by Cz method, were obtained. The transmittance of grown crystals above 500 nm was above 70%. The standard deviation (σ) of the scintillation light output at each position of the 50-mm-long sample was found to be within ±16%.

Numerical investigation of impact of crystal diameter fluctuations on intrinsic point defects distribution in Si crystal grown by Czochralski method

Intrinsic point defects distribution is primarily controlled by the crystal pulling rate and temperature gradient directly at growth interface in silicon crystals grown using the Czochralski (Cz) method. The fluctuation in crystal diameter during the Cz process is one of the primary features associated with the temporal variation in growth process parameters, such as the pulling rate and heater power in the growth system, and which is expected to affect the thermal stress, defects, and dopant incorporation in a growing crystal. In this study, we numerically investigated the effect of temporal variation in crystal diameter on the intrinsic point defects distribution in a silicon crystal grown using the Cz method. The point defect dynamics in the crystal were numerically evaluated within a two-dimensional axisymmetric unsteady global heat and mass transport model for dynamically pulled silicon crystals, considering the shape of the crystal and diameter variation. Unsteady numerical simulations showed that the distribution of intrinsic point defects near crystal side surface in a growing silicon crystal significantly depends on the temporal variation in the crystal diameter.