Czochralski Pulling Technique Research Articles

Single crystal growth of 4-aminobenzophenone (ABP) by micro-capillary Czochralski melt technique for second harmonic generation (SHG) applications

Single crystal of 4-aminobenzophenone (ABP) was grown by micro-capillary Czochralski (mc-CzT) pulling technique from melt using a laboratory designed mini-Czochralski crystal puller set-up with its seed-rod attached with micro-capillary tube. The capillary action of the melt at the tip of the micro tube was carefully controlled in such a way that a single crystal nucleation was induced at the melt interface. Optimization of the melt temperature along with successive control of the rotation and upward pulling rates of the micro-capillary tube led to a successful single crystal growth of ABP. Crystal structure of the grown ABP was confirmed by single crystal X-ray diffraction (SCXRD) structural refinement and the molecular packing stability in the unit cell was studied through intermolecular hydrogen bonding interactions via theoretical means. Further, powder X-ray diffraction (PXRD), UV–visible-near IR (UV–vis-NIR), Fourier-transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) analyses were carried out to confirm the crystalline purity, optical transparency, modes of molecular vibrations and thermal stability of the grown crystal. Kurtz and Perry technique was used to study second harmonic generation (SHG) ability of the grown ABP crystal and found that the SHG efficiency was about 15 times that of potassium dihydrogen phosphate (KDP) and 5 times that of urea.

Single Crystal Growth of 4‐Aminobenzophenone (ABP) by Solution and Seeded Czochralski Pulling Techniques for Second Harmonic Generation Applications

AbstractHighly efficient 4‐aminobenzophenone (ABP) single crystals are grown from melt by employing the seeded Czochralski pulling technique for second harmonic generation (SHG) applications. The as‐grown seed crystals from solution with dominant (100) and (001) facets are utilized to trigger the directional solidification. For successive growth, initial measurements of the furnace temperature distribution, heat flow structure, and solidification temperature of ABP in correlation with differential scanning calorimetry (DSC) analysis are made. The controlled diffusion is ensured by monitoring the interfacial layer between the melt and the growing crystal and is maintained by optimizing the melt temperature and pulling and rotation rates. Color change of the melt due to thermal‐oxidation is prevented by appropriate control of the growth environment. A slow and steady growth rate affirms the good quality of the ABP single crystal. The anisotropic growth behavior of ABP from solution and melt is reported. Internal molecular structure, crystalline purity, molecular vibrational modes, optical transmission, and thermal behavior are studied using single crystal and powder X‐ray diffraction, FTIR, UV–vis–NIR and DSC analyses. The obtained higher SHG efficiency of the grown ABP in comparison with that of the organic and inorganic standards urea and KDP reveals its suitability for SHG applications.

Nd-doped structurally disordered YSr3(PO4)3 single crystal: Growth and laser performances

Disordered-structure crystals have drawn increasing attention as promising ultrashort laser material hosts owing to their broad linewidth. Herein, a novel disordered Nd:YSr3(PO4)3 (Nd:YSP) crystal with good quality was successfully grown via the Czochralski pulling technique. The absorption and fluorescence spectra of the Nd:YSP single crystal were recorded at ambient temperature. The maximum absorption cross section for Nd:YSP single crystal is found to be approximately 3.89 × 10−20 cm2. The stimulated emission cross section for Nd:YSP crystal at ∼1060 nm was determined to be 7.64 × 10−20 cm2 with the full width half maximum value of 22 nm. The fluorescence lifetime of the Nd3+ ions in the Nd:YSP crystal is fitted to be 288 μs. Diode-pumped continuous-wave laser operation is firstly realized at approximately 1060 nm. The maximum output power value from the Nd:YSP crystal is 714 mW, corresponding to a slope efficiency of ∼12.8%. The results indicate that the Nd:YSP crystal with a disordered structure may be a promising disordered laser host.

Single Crystal Growth of N‐Benzyl‐2‐methyl‐4‐nitroaniline by Seeded Czochralski Pulling Technique for NLO and THz Applications

AbstractSingle crystal of N‐benzyl‐2‐methyl‐4‐nitroaniline (BNA), a potential organic nonlinear optical (NLO) material for terahertz (THz) pulse generation, is grown successfully from diffusion controlled melt environment by Czochralski pulling (Cz) technique and is reported for the first time. A solution grown crystal having habitual morphology is used as a seed with pre‐determined crystal rotations at constant melt temperature of 102 °C. Unit cell structure of melt grown BNA is refined using single crystal X‐ray diffraction (SCXRD) analysis and is compared with that of the solution grown one. Crystal packing with the dominance of intermolecular hydrogen bonding such as C─H…O, N─H─O, and C─H…π is examined using 2D finger print (FP) plot and 3D Hirshfeld surface (HS) analysis. The presence of minimal percentage of voids reflects the good stacking of molecular arrangement in the melt grown crystals when compared to the solution grown ones. Crystalline purity is confirmed by powder X‐ray diffraction (PXRD) analysis. Modes of vibrations of different functional groups present and wide optical transparency of the grown BNA are realized using Fourier‐transform infrared (FTIR) and ultraviolet‐visible‐near infrared (UV–vis–NIR) spectroscopic analyses, respectively. Thermal stability and melting point are confirmed through differential scanning calorimetry (DSC).

Structural and photoluminescence studies on europium-doped lithium tetraborate (Eu:Li2B4O7) single crystal grown by microtube Czochralski (μT-Cz) technique**Project supported by the Department of Science and Technology–Science and Engineering Research Board (Grant No. SR/S2/LOP-0012/2011), the Government of India for Awarding Major Research Project, the University Grants Commission–Department of Atomic Research–Consortium for Scientific Research (Grant No. CSR–KN/CSR–63/2014–2015/503), and the Kalpakkam and Indore, India.

Rare earth europium (Eu3+)-doped lithium tetraborate (Eu:Li2B4O7) crystal is grown from its stoichiometric melt by microtube Czochralski pulling technique (μT-Cz) for the first time. The grown crystals are subjected to powder x-ray diffraction (PXRD) analysis which reveals the tetragonal crystal structure of the crystals. UV–vis–NIR spectral analysis is carried out to study the optical characteristics of the grown crystals. The crystal is transparent in the entire visible region, and the lower cutoff is observed to be at 304 nm. The existence of BO3 and BO4 bonding structure and the molecular associations are analyzed by Fourier transform infrared (FTIR) spectroscopy. The results of excitation and emission-photoluminescence spectra of europium ion incorporated in lithium tetraborate (LTB) single crystal reveal that the observations of peaks at 258, 297, and 318 nm in the excitation spectra and peaks at 579, 591, 597, 613, and 651 nm are observed in the emission spectra. The chromaticity coordinates are calculated from the emission spectra, and the emission intensity of the grown crystal is characterized through a CIE 1931 (Commission International d’Eclairage) color chromaticity diagram.

A newer approach of growing methyl-p-hydroxybenzoate (p-MHB) single crystals from a melt without a polymorphic change in their form

As a newer approach, single crystals of methyl-p-hydroxybenzoate (p-MHB), an efficient organic non-linear optical material, were grown from a melt by employing the Czochralski pulling technique for the first time. A specially designed mini-Czochralski crystal puller and a locally designed muffle furnace having a temperature controlling accuracy of ±0.1 °C were used for the experiment. Different types of seeding mechanisms were employed using: (i) micro tubes, (ii) portion of melt grown crystal boules and (iii) previously grown smaller dimensional single crystals from solution as seeds. Crystal growth conditions were optimized on a trial and error basis and bell shaped single crystal boules were successfully grown. The unit cell parameters of the grown crystals were determined by a powder X-ray diffraction (PXRD) study and the internal crystallographic structure was confirmed by single crystal X-ray diffraction (SCXRD) analysis. Comparison of the XRD results with that of the solution grown crystal reveals that no change in the crystal form except small variation in the lattice parameters. Fourier transform infrared (FT-IR) spectral analysis reveals the presence of various functional groups in the grown crystals. Differential scanning calorimetry (DSC) analysis confirms the thermal stability of the grown crystals in the temperature range 30–120 °C. Second harmonic generation (SHG) efficiency of the solution crystals and the melt grown crystals were studied by the Kurtz Perry powder method with a 1064 nm Nd:YAG laser beam as a fundamental source and were found to be nearly equal and about 1.64 and 1.58 times higher, respectively, than that of the inorganic standard potassium dihydrogen phosphate (KDP).

Optical Characterization of Erbium Doped KY<sub>3</sub>F<sub>10</sub> Fluoride Single Crystals

Preparation and optical characterisation of Erbium doped KY3F10 single crystals are reported. The crystals were grown using the Czochralski pulling technique. The single phase was controlled by X-ray diffraction analysis. Room temperature optical spectra were recorded between 200 and 1600 nm. They were used to fit the three phenomenological Judd-Ofelt (JO) parameters Ωt (t = 2, 4, 6). The emission transition probabilities, branching ratios and radiative lifetimes are then deduced. The possibility to use such material for laser emissions is discussed.

Czochralski growth and scintillation properties of Bi4Si3O12 (BSO) single crystal

We have successfully grown crack free BSO (Bi4Si3O12) single crystal using Czochralski pulling technique. A detailed description of the crystal growth procedure and the solutions of the difficulties during the growth process are presented. Results of X-ray diffraction (XRD) showed a single phase of the grown crystal. Photoluminescence and X-rays induced emission spectrum showed a broad emission band in the wavelength range from 350 to 650nm. The energy resolution for 662keV gamma rays is measured to be 22% (FWHM) at room temperature. We measured a light output of 1400 photons/MeV for absorbed γ-ray energy. The decay time spectrum contained three components of 2.2ns (2%), 78.4ns (42%) and 125.6ns (56%) at room temperature.

A proper solution to study the etch pits on LiAlO 2 single crystal

Detailed structures of the etch pits on the (1 0 0), (0 1 0), and (0 0 1) surfaces of LiAlO 2 single crystals have been studied. The crystal was grown by the Czochralski-pulling technique. Hot water is found to be a good etching solution for LiAlO 2 crystal. On the (1 0 0) surface, many shallow rhomboidal etch pits with a deep rhombic pit at the center are revealed and can line up to form boundaries. These etch pits are categorized into two groups which are symmetric relative to the [0 1 0] direction and are separated by boundaries made up of dense etch pits. On the (0 0 1) surface, square pyramid-like etch pits are present. However, rectangle-like etch pits are found on the (0 1 0) surface, which may not be related to dislocations. The density and the distribution of dislocations are studied. A scheme of the domain structure is proposed to explain the observed shapes and distributions of etch pits.

The Growth and Characterization of the Cerium Contained Inorganic Halide Scintillators

A report on the crystal growth, luminescence and scintillation characteristics of two developed scintillators, CsCe2Cl7 and Cs2NaCeCl6 are presented. CsCe2Cl7 is a new scintillation material. These crystals were grown by the Czochralski pulling technique. The X-ray diffraction technique was used to verify the structure of crystals. Under the X-ray excitation emission, the CsCe2Cl7 showed a broad emission band in the wavelength range from 370 to 470 nm while the Cs2NaCeCl6 crystal showed a spectrum in the wavelength range from 370 to 440 nm. The energy resolutions (FWHM of peak position) for the 662 keV full energy peak of 5.5% and 8.3% were observed at room temperature for the CsCe2Cl7 and Cs2NaCeCl6 crystals, respectively. The scintillation decay time measurement curves showed that, CsCe2Cl7 crystal has a single exponential decay function with a decay time of 50 ns. The Cs2NaCeCl6 crystal exhibited three main decay time components, a short component with a decay time constant of 91 ns and 36% intensity, an intermediate component with a decay time constant of 601 ns and intensity 33%, followed by a long component with a 3.2 µs decay time constant and an intensity of 31% of the total light yield. On the basis of the scintillation results of these materials grown, it is believe that these scintillation crystals can find a place in medical imaging and radiation detection system.

Thermal Wave Measurements with a Mirage Detection for Investigation of Thermal Diffusivity of GdCa4O(BO3)3Single Crystals

Single crystals of GdCa4O(BO3)3 were examined to determine their thermal properties. Samples were grown by the Czochralski pulling technique. There were three types of samples: a pure crystal, the crystal doped with neodymium (4 at.% of Nd), and the third one doped with ytterbium (7 at.% of Yb). All samples were rectangular prisms with edges parallel to the axes of the optical indicatrix X, Y , Z (principal axes). The thermal diffusivity was determined by means of the thermal wave method with the optical detection of the temperature disturbance based on a mirage effect. Experimental results showed anisotropy of the thermal diffusivity. The thermal diffusivity along Y direction has the highest value while values obtained in X and Z axes are much lower. Dopants cause decrease in the thermal diffusivity for all investigated directions.

Gadolinium calcium oxyborate piezoelectric single crystals for ultrahigh temperature (>1000 °C) applications

ReCa 4 O ( BO 3 ) 3 oxyborate crystals (ReCOB, where Re is a rare earth element such as Gd) were grown using the Czochralski pulling technique. The crystals belong to Cm space group and the relationships of the as-grown crystal morphology with crystallographic and physical coordinates were determined. The optimum length extensional and thickness shear vibrations of GdCOB were found for (ZYl)40° and (YXt)33° cuts, with electromechanical coupling factors k32 and k26, being on the order of 17.5% and 25% and piezoelectric coefficients d32 and d26 around −4.5 and 11.7 pC/N, respectively. Of particular significance is the nearly temperature independent behavior up to >1000 °C. Together with its high resistivity (∼5×106 Ω cm at 1000 °C) and high mechanical quality factor (∼4000 at 1000 °C) make GdCOB and/or ReCOB crystals promising candidates for the next generation sensing applications at ultrahigh temperature (>1000 °C).

Crystal growth and properties of LiAlO2 and nonpolar GaN on LiAlO2 substrate

In this study, the growth and properties of LiAlO2 material and a nonpolar GaN-based light-emitting-diode (LED) structure on LiAlO2 have been investigated. The LiAlO2 material is grown by the Czochralski pulling technique and is used as a substrate for nonpolar nitride growth. An improved surface roughness can be obtained by a four-step polishing process. With subsequent nitridation treatment, a pure M-plane (101̱0) GaN can be obtained. An electron microscope shows an abundance of cracks that are oriented parallel to the (001) and (100) planes of the LiAlO2 substrate on the rear surface of GaN. The absence of the polarization-induced electric field of a GaN-based LED structure on LiAlO2 was shown by using photoluminescence measurements. Therefore, this approach is promising to further increase the luminescence performance of GaN-based LEDs.

Crystal growth and spectroscopic investigations of Tm3+ ions doped 5NaF-9YF3 fluoride single crystals

The Tm3+:5NaF-9YF3 single crystals were grown by Czochralski pulling technique after purification of the starting materials. The obtained crystals are of good optical quality. Optical absorption of this material is investigated. The Judd–Ofelt (JO) analysis was applied to the room temperature absorption intensities of Tm3+ ions to determine the so-called JO intensity parameters and the transition strengths. These JO parameters are used to calculate the radiative transition probabilities, the radiation lifetimes and the branching ratios. The results obtained indicate that Tm3+:5NaF-9YF3 may be considered as a laser active material.

Investigations of NCPM second harmonic generation and self frequency doubling in Gd1−x−yRxNdyCa4O(BO3)3 (R = Sc or Lu) crystals

Pure and Nd3+ doped single crystals of Gd1−xRxCa4O(BO3)3 (R3+=Sc3+ or Lu3+) with large size and good quality have been grown by the Czochralski pulling technique. By changing the compositional parameter x of Gd1−xRxCa4O(BO3)3 crystals, their optical birefringence can be controlled in order to achieve non-critical phase matching (NCPM) in the ranges of 790–824nm along Y-axis and 920–963nm along Z-axis, during second harmonic generations. Nonlinear optical properties of these new biaxial borate crystals are reported. Preliminary investigations of self frequency doubling in NCPM condition in Gd1−x−yRxNdyCa4O(BO3)3 crystals have been carried out.

Ising-axis conversion in [formula omitted

The so-called Ising-axis conversion is an irreversible metamagnetic transition observed in the orthorhombic antiferromagnets RCu 2 ( R = lanthanide ) in high magnetic fields applied along the hard axis of magnetization. In fields parallel to the crystallographic c -axis it converts the magnetic Ising axis from the a - to the c -direction for R = Ce , Pr, Tb and Dy. This transition is accompanied by a giant magnetostriction effect ( Δ L / L ≈ 1 % ) and the new state remains stable even after switching off the field. The axis conversion process is not limited to the ordered region only and occurs also in the paramagnetic range. To study the competition between the magnetic and the quadrupolar interactions an Y-diluted system is studied. High-quality single crystals of the ( Tb 0.5 Y 0.5 ) Cu 2 compound were grown by the Czochralski pulling technique and subjected to the specific heat, magnetization, neutron diffraction and axis-conversion experiments. The dilution of the Tb sublattice leads to weakening of the magnetic exchange, manifested by lowering of the Néel temperature from T N = 54 K in pure TbCu 2 to T N = 30 K in ( Tb 0.5 Y 0.5 ) Cu 2 , while the magnetic ground state structure remains unchanged. The Ising-axis conversion has been studied by magnetization measurements. The c -axis-magnetization curve exhibits several metamagnetic transitions corresponding to the conversion of the easy-axis of magnetization. The temperature dependence of the critical fields is well comparable to that of the pure TbCu 2 . From the experiments follows that the quadrupolar interaction is the driving force of the conversion process.

Feasibility study on Czochralski (Cz) growth of 3-methoxy 4-hydroxy benzaldehyde (MHBA) single crystals for nonlinear optical applications

Reported large nonlinear optical coefficients such as d 22 = 23.8 d 36 KDP, d 21 = 13.5d 36 KDP, d 23 = 29.1 d 36 KDP, d 25 = 12.8 d 36 KDP of 3-methoxy 4-hydroxy benzaldehyde (MHBA) attract research on its bulk crystal growth for device application. The X-ray rocking and X-ray topographic studies of Cz-grown organic monoclinic crystals invariably reveal closely aligned sub-crystals which made melt growth difficult. In this context, the single crystal growth of MHBA by Czochralski pulling technique has been successfully demonstrated for the first time in the literature. Comparison study of obtained X-ray powder diffraction data with the literature confirmed the monoclinic structure. High-resolution X-ray diffraction (HRXRD) study confirms the better crystalline perfection of the grown crystal in comparison to that of solution-grown crystals and revealed the optimization of the growth process along [211¯] direction. TG, DTA and optical transmission studies carried out on the grown crystal exhibit its thermal and optical properties for SHG application.

Optical frequency doubling in microtube Czochralski (μT-CZ) grown benzophenone single crystals

Microtube Czochralski pulling technique (μT-CZ) is a novel method of growing bulk organic single crystals using microtube as a seed. This technique was successfully utilized for the bulk growth of benzophenone single crystals, which is a potential organic non-linear optical material. The important growth parameters were optimized for the present system. The optimized growth parameters are as follows: pulling rate, 1–2 mm/h; seed rotation rate, 10 rpm; and the axial thermal gradient, 8 °C/cm. X-ray rocking curve studies on the cut and polished wafers made out of the grown crystals confirm better crystalline quality. Fourier transform infrared spectroscopy was performed to ascertain the functional groups and UV–VIS–NIR spectroscopy was carried out to evaluate the optical quality of the grown sample. Powder second harmonic generation (SHG) measurement shows that the grown samples exhibit nearly three times higher SHG than potassium dihydrogen phosphate (KDP).

Czochralski growth and characterization of neodymium-doped strontium lanthanum aluminate (ASL:Nd) single crystals

Nd-doped strontium lanthanum aluminate crystals, Nd:ASL (Sr 1− x Nd y La x − y Mg x Al 12− x O 19), with an extended composition parameter x (0.05 and 0.5) have been grown by the Czochralski pulling technique. Structural and compositional properties of the as-grown crystals have been studied using X-ray diffraction, chemical microanalysis and optical spectroscopy. The results show that high crystalline perfection and large size crystals of both compositions can be grown. Low-temperature optical absorption spectra of crystals with compositions corresponding to x = 0.5 and 0.05 reveal that such crystals predominantly contain either C 1- or C 2-type Nd 3+-centers, respectively. The possibility to thus differentiate between the two types of the dopant structural centers is of utmost importance for laser applications.

Microtube-Czochralski (μT-CZ) growth of bulk benzophenone single crystal for nonlinear optical applications

Microtube-Czochralski technique was employed to grow large size benzophenone single crystal for the first time. In conventional Czochralski pulling technique, the growth of bulk single crystal will be initiated by a pre-grown seed, whereas in microtube-Czochralski technique a microtube that is made out of a metal such as stainless steel (8 μm ID) can be used to grow bulk single crystal. A specially designed furnace having inert gas atmosphere, condensation free enclosure and in situ annealing facility was employed. Benzophenone crystal having cubic facet (15 mm) with high optical quality was grown when the following vital growth parameters are set to the corresponding optimized values such as pulling rate: 1–2 mm/h, seed rotation rate: 5–10 rpm and the axial thermal gradient: 8 °C/cm. The grown crystals were cut and polished. Thin plate like polished samples were used to justify the optical quality of the grown samples by UV–VIS–NIR spectroscopy. Powder SHG measurement shows that the grown samples exhibit three times higher second harmonic generation than potassium dihydrogen phosphate (KDP).