Cz Method Research Articles

Effects of gallium substitution on crystal growth and properties of gehlenite single crystal

Gehlenite crystal, Ca2Al2SiO7 (CAS) crystal is found to be appropriate material to high temperature piezoelectric sensors, for its high electrical resistivity and high temperature stability of piezoelectric coefficients. But the challenges of growing high quality single crystal and the fragile characteristics limited its broad application and mass production in future. In this paper, a new member of the melilite family, bulk Ca2Al2-xGaxSiO7 (CAGS) single crystal, was successfully grown by the Czochralski (Cz) method, without any bubble, inclusion and cracking. By a small fractional of gallium substitution, we obtained a new potential high temperature piezoelectric single crystal CAGS with larger pulling rate (more than twice that of CAS), and better quality of single crystal. Furthermore, the dielectric and piezoelectric properties of CAS and CAGS single crystals were measured and compared. The measured piezoelectric coefficient d14 of CAGS single crystal is 10.52 pC/N which is much higher than that of CAS (6.68 pC/N). The electrical resistivity of CAGS was found to be remarkably high, reaching a value of ∼2.3 × 109 Ω cm at 600 °C.

Unsteady numerical simulations considering effects of thermal stress and heavy doping on the behavior of intrinsic point defects in large-diameter Si crystal growing by Czochralski method

Abstract We conducted unsteady simulations of intrinsic point defect dynamics considering the effects of the thermal stress and dopant concentration in a large-diameter silicon crystal growing by the Czochralski (Cz) method. The thermal equilibrium concentration of the intrinsic point defects (vacancy, V, and self-interstitial Si atom, I) was simulated as a function of the thermal stress and the incorporated dopant concentration in a growing Si crystal, which was obtained through ab-initio calculations. Furthermore, point defect dynamics in the crystal were solved within a two-dimensional axisymmetric unsteady global heat and mass transport model by considering the thermal stress and the incorporation of a dopant using segregation for dynamically pulling Si crystal by the Cz method. The unsteady numerical simulations showed that the formation and the distribution of intrinsic point defects depend on the temporal variation of the thermal stress and the incorporated dopant concentration in a growing Si crystal.

Polarized spectral properties of Sm:YAlO3 single crystal for reddish-orange laser

Sm:YAlO3 (Sm:YAP) crystal with size of Φ28 × 80 mm3 was grown by Czochralski (Cz) method. Polarized absorption spectra and fluorescence spectra of Sm:YAP crystal were discussed for the first time. The peak emission cross-sections were calculated to be 0.80 × 10−21 cm2 (604 nm for a-polarization), 1.82 × 10−21 cm2 (604 nm for b-polarization) and 1.63 × 10−21 cm2 (610 nm for c-polarization), respectively. The Judd-Ofelt (JO) intensity parameters were calculated to be Ω2 = 2.59 × 10−20 cm2, Ω4 = 1.78 × 10−20 cm2 and Ω6 = 2.98 × 10−20 cm2, respectively. The decay lifetime of 4G5/2 energy level was measured to be 2.51 ms. All above results indicate the Sm:YAP crystal may be a potential candidate of reddish-orange laser pumped directly by the GaN/InGaN laser diode.

Numerical analysis of effect of thermal stress depending on pulling rate on behavior of intrinsic point defects in large-diameter Si crystal grown by Czochralski method

We analyzed the effects of thermal stress and pulling rate on the behavior of intrinsic point defects in a silicon (Si) single crystal grown by the Czochralski (Cz) method using a numerical approach. The thermal equilibrium concentration of the intrinsic point defects (vacancy, V, and self-interstitial Si atom, I) was simulated as a function of thermal stress, which was obtained via ab -initio calculations. Furthermore, the point defect dynamics in the crystal were solved within a framework of a two-dimensional (2D) axisymmetric steady-state global heat and mass transport model of Si crystal growth by the Cz method. The numerical simulations revealed that both magnitude and distribution of the thermal stress depend on the pulling rate. Moreover, they impact the formation and distribution of intrinsic point defects in a growing Si single crystal.

Growth, spectroscopic, diode-pumped mid-infrared laser properties of Er:GSAG crystal

A great potential mid-infrared laser crystal of heavily Er3+ doped GSAG crystal with high optical quality is successfully grown by Cz method. The crystal quality of Er:GSAG crystal is determined by XRC. The structure parameters of Er:GSAG crystal are obtained by the X-ray Rietveld refinement method (a = b = c = 12.3196 Å). The absorption cross section at 961 nm and 967 nm are 0.381 × 10−21 cm2 and 0.414 × 10−21 cm2, respectively. The 962 nm laser diode end-pumped Er:GSAG laser operated at 2828 nm is demonstrated for the first time. The performance of Er:GSAG laser is investigated in great detail. A maximum output power of Er:GSAG laser is 410 mW when pumped by 962 nm LD at 300 Hz and 0.5 ms. Simulating results display the highest temperatures of Er:GSAG laser spot is 345.8 K, indicating a small thermal lensing effect of Er:GSAG crystal. Besides, the laser performance of Er:GSAG crystals which irradiate by different doses of gamma-ray are used to investigated its potential for working in the radiation resistance environment. The results show the relatively minor differences on the Er:GSAG lasers performance, indicating a great potential of Er:GSAG crystal in radiant environment application.

Surface Treatments and Modifications of Si Wafers Produced by Czochralski Method for Solar Cell Applications

The objective of this work is to carry out surface treatments and modification of single-crystal silicon (Si) wafers produced by the Czochralski (Cz) method for solar cell applications. Lapping and polishing processes were performed on Si wafers for removing saw damages which occurred when sliced Si ingot was grown in the Cz system. The appropriate time and speed for the slicing process were determined as a result of parameter studies. The wet texturing process was generated with different durations on the surface of lapped and polished Si wafers to acquire square-based pyramidal structures for preventing losses from incoming sunlight which is necessary for solar cell applications. An x-ray diffractometer, scanning electron microscope, surface profilometer, and UV–Vis spectrophotometer were employed for characterizations of all processes. The results show that single-crystal Si wafers were successfully produced by the Cz method, and after the texturing process, roughness and reflectance values of the wafers significantly decreased. The wafers could be potential candidates for economical mass production.

Growth and properties of TSAG and TSLAG magneto-optical crystals with large size

Large size high transparent TSAG and TSLAG single crystals of Ø 65 mm × 70 mm have been grown successfully by the Cz method. The refractive indices at 473, 532, 632.8 and 1064 nm are 1.9214 - 1.8817 for TSAG and 1.9242 - 1.8841 for TSLAG. Their Sellmeier equations are fitted. The average thermal expansion coefficients of TSAG and TSLAG at 300 – 373 K, 300 – 473 K, 300 – 573 K, 300 – 673 K, and 300 – 773 K are measured. The values of thermal expansion coefficients of TSAG and TLSAG crystals coincide within the measurement error (differ by 0.3–0.4%). The thermal diffusivity values of TSAG and TSLAG are 1.454 and 1.418 mm2 s−1 at 300 K, respectively. Calculated with the specific heat results, the values of thermal conductivity of TSAG and TSLAG are 4.45 and 4.20 W (m K)−1 at 300 K. Moreover, the Verdet constants of TSAG are 218, 152, and 65 rad/m/T at 532, 633, and 1064 nm, while those of TSLAG are 246, 146, and 56 rad/m/T, respectively. In further, the relationships between Verdet constant and wavelength of TSAG and TSLAG are obtained.

Fabrication of Medium Power Insulated Gate Bipolar Transistors Using 300 mm Magnetic Czochralski Silicon Wafers

The use of silicon wafer substrates with a diameter of 300 mm for the manufacturing of electronic devices strongly increases the overall productivity of a device manufacturing line. However, float‐zone (FZ) silicon, which is traditionally used for insulated gate bipolar transistors (IGBTs), is not available for wafer diameters exceeding 200 mm. Therefore, a silicon material fabricated by the magnetic Czochralski (m:Cz) method has to be used for IGBT production on 300 mm wafers. Critical issues of this material are the so‐called crystal originated particles (COPs) and the strong axial variation of the doping level along the crystal. Furthermore, the m:Cz material contains a relatively high concentration of oxygen so that the influence of carbon/oxygen complexes has to be considered. CIOI complexes can be decorated with hydrogen atoms, resulting in donor‐like complexes. In particular, the application of proton irradiation for the doping of the field‐stop zone results in a relatively high concentration of interstitial carbon, which is continuatively associated with the generation of undesired donors. It is shown that the electrical behavior of IGBTs fabricated on FZ substrates can be well reproduced using the m:Cz material if the parameters of the hydrogen implantation are adjusted appropriately.

Crystal growth, thermal and optical properties of TSLAG magneto-optical crystals

Tb3Sc1.95Lu0.05Al3O12 (TSLAG) magneto-optical crystal, with higher Verdet constant and lower absorption coefficient, is a potential candidate to substitute the commercial TGG crystals. In this work, bulk TSLAG crystals with maximum dimensions of Ø 35 × 60 mm3 have been successfully grown by the Czochralski (Cz) method with a 60 mm diameter crucible. The effective segregation coefficient of Tb3+, Sc3+, Lu3+, Al3+ ions were 0.99, 0.87, 0.99 and 1.09, respectively. The use of pure starting materials and lower thermal gradients during growth led to significantly improved crystal properties such as the optical transmission characteristics at 1064 nm. Also the thermal properties have been investigated in detail, providing primary reference data for applications in the field of intense lasers.

Spectra properties of Yb3+, Er3+: Sc2SiO5 crystal**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFB0701002), the Joint Fund of the National Natural Science Foundation of China and China Academy of Engineering Physics (NSAF) (Grant No. U1530152), the National Natural Science Foundation of China (Grant Nos. 91222112 and 61475177), and Shanghai Rising-Star Program (B type),

The influence of Er3+ ions on the spectra of Yb3+, Er3+: Sc2SiO5 (SSO) single crystal, which was obtained by Czochralski (Cz) method, is discussed. The absorption coefficient at 980 nm was 13.36 cm−1 with a peak absorption cross-section of 1.46 × 10−20 cm2. The emission cross-sections at 1034 nm and 1062 nm were 5.5 × 10−21 cm2 and 4.9 × 10−21 cm2, respectively. The fluorescence lifetime was estimated as 1.24 ms at 1061 nm. The mechanical properties of SSO single crystal were also presented.

Enhancement of magneto-optical performance of Tb0.94Pr0.06VO4 single crystals by Pr doping

Tb0.94Pr0.06VO4 (TPV) magneto-optical crystal with sizes of 27 × 35 mm3 was grown by the Czochralski (Cz) method. Its structure was verified by Powder X-ray diffraction, demonstrating that TPV belongs to tetragonal system. The optical and magneto-optical properties were systematically investigated. TPV exhibits high transparency in the near-infrared region. The Verdet constants of TPV at 633 and 1064 nm are about 60% larger than that of TGG. The thermal conductivity and laser-induced damage threshold of TPV were also determined for evaluating its practical usage. All the results indicate that TPV is a promising Faraday rotation material for magneto-optical applications in high power laser systems.

Growth rate effect on colony formation in directional solidification of Al2O3/YAG/ZrO2

AbstractMechanical properties of Al2O3/Y3Al5O12/ZrO2 ternary eutectic ceramics are strongly affected by structural defects as pores or colonies. Experimental investigation of the microstructure of this ternary composite indicates that the colonies are generally observed when the solidification occurs at high rates. In this work, the influence of the growth rate on the solid‐liquid interface shape and formation of colonies in directional solidification of Al2O3/Y3Al5O12/ZrO2 by Bridgman, Edge‐defined Film‐fed Growth (EFG), and Czochralski (Cz) methods is numerically and experimentally investigated. Numerical modeling of the Bridgman growth process shows large curvatures of the solid‐liquid interface when the pulling rate is increased up to 80 mm/h. The ingots solidified at rates between 5 and 80 mm/h exhibit colony type microstructure. The analysis of EFG growth of ceramic ribbons reveals less curved solid‐liquid interfaces in this system. Numerical modeling shows significant increase in the interface curvature with increasing pulling rate. The microstructure of ribbons grown at pulling rates between 6 and 12 mm/h exhibits colonies only for the ingots solidified at higher rate. Simulations carried out for Czochralski growth process show that the solidification front is almost plane in this system. These results are in agreement with experimental observations showing good structural quality of Cz grown crystals with a flat solid‐liquid interface. Finally it is concluded that formation of colonies in directional solidification of this ternary eutectic composite is linked to large curvatures of the growth interface.

Determination of phonon deformation potentials and strain-shift coefficients in Ge-rich Si1−xGex using bulk Ge-rich Si1−xGex crystals and oil-immersion Raman spectroscopy

The strain-free Raman shift of the Ge–Ge mode, , of Ge-rich Si1−xGex (x: Ge fraction) was determined accurately from the bulk Ge-rich Si1−xGex samples fabricated by the Czochralski (Cz) method. Using the obtained , the phonon deformation potentials (PDPs), p and q, and the strain-shift coefficient bLO of isotropic biaxial strained Ge-rich Si1−xGex thin films were extracted by oil-immersion Raman spectroscopy using Raman peak shifts of longitudinal and transverse optical (LO and TO) phonon modes. As a result, it was confirmed that these parameters are almost constant with small variations and that the strain-shift coefficient bLO is in good agreement with ab initio calculations. The parameters determined in this work are essential to realize accurate strain measurements using Raman spectroscopy for Ge-rich Si1−xGex devices.

A method for combining p-values in meta-analysis by gamma distributions

ABSTRACTCombining p-values from statistical tests across different studies is the most commonly used approach in meta-analysis for evolutionary biology. The most commonly used p-value combination methods mainly incorporate the z-transform tests (e.g., the un-weighted z-test and the weighted z-test) and the gamma-transform tests (e.g., the CZ method [Z. Chen, W. Yang, Q. Liu, J.Y. Yang, J. Li, and M.Q. Yang, A new statistical approach to combining p-values using gamma distribution and its application to genomewide association study, Bioinformatics 15 (2014), p. S3]). However, among these existing p-value combination methods, no method is uniformly most powerful in all situations [Chen et al. 2014]. In this paper, we propose a meta-analysis method based on the gamma distribution, MAGD, by pooling the p-values from independent studies. The newly proposed test, MAGD, allows for flexible accommodating of the different levels of heterogeneity of effect sizes across individual studies. The MAGD simultaneously retains all the characters of the z-transform tests and the gamma-transform tests. We also propose an easy-to-implement resampling approach for estimating the empirical p-values of MAGD for the finite sample size. Simulation studies and two data applications show that the proposed method MAGD is essentially as powerful as the z-transform tests (the gamma-transform tests) under the circumstance with the homogeneous (heterogeneous) effect sizes across studies.

Crystal growth, polarized spectroscopy and Judd-Ofelt analysis of Tb:YAlO3

Tb3+-doped YAlO3 (YAP) single crystal was grown by Czochralski (Cz) method. Based on the polarized absorption spectra, the spectroscopic parameters were calculated to be Ω2=3.49×10−20cm2, Ω4=5.87×10−20cm2 and Ω6=2.55×10−20cm2, and then the spontaneous transition rate, fluorescent branching ratio and radiative lifetime of 5D4 multiplet were obtained. The yellow emission cross sections of 5D4→7F4 transition were calculated to be 1.72×10−22cm2, 2.73×10−22cm2 and 2.65×10−22cm2 for a, b and c polarization, respectively. The fluorescence lifetime of the 5D4 multiplet was fitted to be 1.72ms. All the data indicate that Tb:YAP crystal is a promising candidate for yellow laser operation.

Countdown before voluntary exercise induces muscle vasodilation with decreased muscle sympathetic nerve activity in humans

We examined whether countdown (CD) before voluntary bicycle ergometer exercise induced cerebro‐cardiovascular responses and, if so, whether these responses to CD were altered by postural change from the semi‐recumbent to supine position. Young men (n=14) performed voluntary cycle exercise in the semi‐recumbent position while middle cerebral artery blood flow velocity (CBF; Doppler ultrasonography), heart rate (HR), blood pressure (finger photoplethysmography), oxygen consumption rate (VO2), oxygen saturation in the right thigh muscle (StO2; near‐infrared spectrometry), cardiac output (CO; cZ method) and total peripheral resistance (TPR) were measured. The subjects repeated 8 trials, intermitted by more than 5‐min rest. In 4 trials randomly selected from 8 trials, the onset of exercise was signaled by a 30‐sec CD, whereas in the remaining 4 trials, exercise was started without CD. We found that CD increased CBF, HR, CO, mean blood pressure, and VO2 sequentially, decreasing TPR with increased StO2. To assess efferent signals causing vasodilation and the effects of posture change from the semi‐recumbent to supine position, other groups of subjects underwent the same exercise protocol but using only right leg in the semi‐recumbent (n=10) or supine (n=8) positions while muscle sympathetic nerve activity (MSNA; microneurography) and StO2 were measured in the left and right leg, respectively. We found that CD decreased MSNA burst frequency and total MSNA (both, P<0.05), which were significantly correlated with the increase in StO2 (both, P<0.001). However, these responses to CD were nearly abolished by the postural change. Thus, CD before starting voluntary exercise induced cerebro‐cardiovascular responses from central system to effector organs in a sequential manner in the semi‐recumbent position, but these responses were minimized while in the supine position.Support or Funding InformationThis study was supported by grants from the Japan Society for the Promotion of Science (24689014 and 15H04680).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Crystal growth and piezoelectric properties of Ca3Ta(Ga0.9Sc0.1)3Si2O14 bulk single crystal

Ca3Ta(Ga0.9Sc0.1)3Si2O14 langasite-type single crystal with a diameter of 1 in. was grown by Czochralski (Cz) method. Obtained crystal had good crystallinity and its lattice constants exceeded those of Ca3TaGa3Si2O14 (CTGS) according to the X-ray analysis. A crack-free specimen cut from the grown crystal was used for the measurements of dielectric constant ε11T/ε0, electromechanical coupling factor k12, and piezoelectric constant d11. The accuracies of these measurements were better than those for the crystal grown by micro-pulling-down (μ-PD) method. Substitution of Ga with Sc resulted modification of these constants in the directions opposite to those observed after partial substitution of Ga (of CTGS) with Al. This suggests that increase of |d14| was most probably associated with enlargement of average size of the Ga sites. The crystal reported here had greater dimensions as compared to analogous crystals grown by the μ-PD method. As a result, accuracy of determination of acoustic constants of this material may be improved.

Crystal growth, polarized spectroscopy and Judd-Ofelt analysis of Pr:YAlO3

Pr3+-doped YAlO3 (YAP) single crystal was successfully grown by the Czochralski (Cz) method. Polarized absorption and polarized fluorescence spectra were measured at the room temperature. The spectroscopic parameters based on the polarized absorption spectra were calculated by Judd-Ofelt (J-O) theory for the first time. The fluorescence lifetime of 3P0 energy level was fitted to be 19.16μs with the quantum efficiency of 95.8%. Through the analyzing of the spectroscopic properties, Pr:YAP crystal was demonstrated to be a promising candidate for solid state laser operation.

A novel crystal Tm: Lu0.8Gd0.8Y0.4SiO5 with potential for broadband tunable lasing

A novel Tm3+ -doped crystal Lu0.8Gd0.8Y0.4SiO5 (Tm: LGYSO) was grown by the Czochralski (Cz) method. The full width half maximum (FWHM) of the Tm:LGYSO crystal around 2 μm was as broad as 280 nm, which is the broadest FWHM among the Tm3+ doped crystals have been reported, to the best of our knowledge. The crystal growth, structure, absorption spectra, J-O parameters, emission spectra and fluorescence lifetime were discussed in details. The absorption cross-section is 1.429 × 10−20 cm2 and the full width half maximum is 8.337 nm at 791 nm. The spectroscopic parameters were calculated using the Judd-Ofelt theory, and the J-O parameters Ω2, Ω4 and Ω6 were found to be 1.615 × 10−20, 2.773 × 10−20 and 0.695 × 10−20 cm2, respectively. An intensity and broad 2 μm emission of the 3F4 → 3H6 transition in Tm: LGYSO crystal was observed with an emission cross-section of 0.73672 × 10−20 cm2 at 1972 nm. The fluorescence decay time of the 3F4 → 3H6 transition was measured to be 1.669 ms. Results suggest that Tm: LGYSO crystal is a promising laser crystal for tunable and ultrafast laser output around the 2 μm wavelength.

Crystal growth, defects, mechanical, thermal and optical properties of Tb3Sc2Al3O12 magneto-optical crystal

Tb3Sc2Al3O12 (TSAG) magneto-optical crystal was grown successfully by the Czochralski (Cz) method. Its structure and crystalline quality were determined by the powder X-ray diffraction and X-ray rocking curve, respectively. The chemical etching method was employed to investigate its defects morphology with phosphoric acid as etchant. Based on the Vickers hardness experiment, the mechanical properties of TSAG crystal (including hardness, yield strength, fracture toughness and brittle index) were systematically estimated. The thermal properties of TSAG crystal in the temperature range of 280–500 K were obtained for the first time, which are valuable for evaluating its applications. The transmission spectrum of the as-grown crystal was measured at room temperature and the transmittance in the wavelength range of 505–1445 nm is found to be as high as 82.3%. All the obtained results will contribute significantly to exploring TSAG crystal that used in high-average-power magneto-optical systems.