Kyropoulos Technique Research Articles

Lateral Inhomogeneities of Sapphire Plates Determined with the Aid of X-Ray and Probe Methods

X-ray diffractometry, X-ray profilometry, atomic-force microscopy, and sclerometer tests are employed in the study of R-cut plates of sapphire single crystals grown with the aid of the Kyropoulos technique and used as substrates for the silicon-on-sapphire structures. Regions with different degrees of perfection can be found even on a single plate. Mutually consistent results of the four experimental methods based on different physical principles can be used to reveal regions of structural imperfection on the surface of a plate. It is expedient to employ a complex procedure for multipoint monitoring of the parameters of plates to reduce the number of defect samples that serve as substrates in the production of electronic devices.

Origin of scattering defect observed in large diameter Ti:Al2O3 crystals grown by the Kyropoulos technique

Abstract Large diameter Ti-doped sapphire single crystals grown by the Kyropoulos technique along the A-axis, show detrimental light scattering close to the central C-plane. Thermo-luminescence measurements evidence that this defect is associated to a high level of oxygen vacancies. X-ray topography and Rocking Curve Imaging were performed. They show that the dislocation number is very small where scattering occurs, compared to the rest of the crystal, in agreement with results of numerical modelling of thermo-elastic stresses during crystal growth. A model is proposed in order to explain the scattering effect, based on the precipitation of nano-voids from vacancies in the absence of dislocations.

Латеральные неоднородности сапфировых пластин по данным рентгеновских и зондовых методов

An R-cut sapphire wafers grown by Kyropoulos technique for fabrication of silicon-on-sapphire structures has been examined with the use of X- ray diffractometry, reflectometry, atomic-force microscopy and sclerometry methods. It is found that areas of different degree of crystal structure perfection are present even within the same wafer. It is shown that the results obtained by four different methods, based on different physical principles, are in good agreement and allow to recognize the areas of imperfect structure on the wafer surface. Implementation of comprehensive control of the quality parameters at several points of wafer surface is justified in order to reduce the production defects in the usage of sapphire wafers for fabrication of semiconductor devices.

Crystal growth, IR specular reflectance and polarized Raman studies of LiNa5Mo9O30 polar single crystal.

A non-centrosymmetric, polar LiNa5Mo9O30 single crystal was grown using Kyropoulos technique and characterized by polarized Raman scattering and polarized infrared specular reflection spectroscopy at room temperature. The comparison to the polycrystalline spectra has been made and assignment of all observed modes to the respective vibrations and their symmetry has been proposed. Based on the four parameter model the infrared reflection spectra were analyzed and the LO-TO splitting has been determined for the observed modes. Stronger anharmonicity of bands assigned to stretching vibrations of the Mo-O⋯Mo bridges has been evidenced. Our results show that this crystal is attractive and promising SRS-active nonlinear optical material for up- and down-Raman laser-frequency converters with the most intense lasing lines at 947 and 884cm-1. Dielectric permittivity studies in the frequency domain exhibit two anomalies that are assigned to thermally activated relaxation and conductivity processes. The observed increase in electrical conductivity above 400K is dominated by ionic contribution and change of the conductivity mechanism.

3D Anisotropic Stress Analysis during Kyropoulos Growth of Sapphire Single Crystal

AbstractBy using 3D finite element calculations, numerical simulations are performed to predict the thermal field as well as the thermal stress in a c‐axis sapphire single crystal grown by Kyropoulos technique. The effects of additional resistive heating (placed under the crucible bottom) and crystal rotation are investigated and a comparison is made between the isotropic and anisotropic analysis. The anisotropy of the elastic constants and thermal expansion coefficients as well as their temperature dependence are considered in the anisotropy calculations while Young's modulus and the Poisson ratio are used in the isotropic analysis. Thermal stress is found to be smaller in the anisotropy analysis than that in the isotropic analysis and significant differences are found in their respective distribution patterns. Additional resistive heating acts to decrease both of the crystal–melt interface convexity and the von Mises stress. In addition, crystal rotation combined with additional resistive heating decreases significantly the thermal stress inside the sapphire crystal and along the melt–crystal interface. Therefore, optimizing the heating conditions and using a suitable crystal rotation rate seem to be favorable to control the growth interface shape and to reduce thermal‐stress‐related defects during the growth process.

Scattering defect in large diameter titanium-doped sapphire crystals grown by the Kyropoulos technique

The convex interface shape in Kyropoulos-grown crystals is suggested to be responsible for the scattering defect in large diameter titanium sapphire.

Titanium distribution profiles obtained by luminescence and LIBS measurements on Ti: Al2O3 grown by Czochralski and Kyropoulos techniques

The titanium distributions in Ti-doped sapphires grown by Czochralski and Kyropoulos techniques were evaluated using Laser-Induced Breakdown Spectroscopy (LIBS) and luminescence characterizations. Distinctly different radial profiles of Ti4+ distribution were observed in the as grown Ti: Al2O3 crystals. The Ti4+ distribution in the crystal grown by Kyropoulos technique was analyzed as a function of the specific of the growth technique, the conclusion is significant for Ti: sapphire on laser application. Kyropoulos technique presents an advantage to reduce the proportion of Ti4+ in Ti: sapphire comparing to Czochralski technique.

Large Ti-doped sapphire single crystals grown by the kyropoulos technique for petawatt power laser application

Large diameter Ti-doped sapphire single crystals were grown by the Kyropoulos technique. The optical characterizations (luminescence, transmittance, evaluation of the FOM) of these bulk crystals are presented. The presented results are promising for the growth of large Ti-doped sapphire crystals by Kyroupolos technology for petawatt scale amplifier.

Single‐crystal sapphire microstructure for high‐resolution synchrotron X‐ray monochromators

We report on the growth and characterization of sapphire single crystals for X‐ray optics applications. Structural defects were studied by means of laboratory double‐crystal X‐ray diffractometry and white‐beam synchrotron‐radiation topography. The investigations confirmed that the main defect types are dislocations. The best quality crystal was grown using the Kyropoulos technique. Therein the dislocation density was 102–103 cm−2 and a small area with approximately 2*2 mm2 did not show dislocation contrast in many reflections. This crystal has suitable quality for application as a backscattering monochromator. A clear correlation between growth rate and dislocation density is observed, though growth rate is not the only parameter impacting the quality.

Research on the multi‐crystalline structure in sapphire grown by Kyropoulos technique

The macroscopic distribution of multi‐crystalline structure (MCS) in a sapphire boule grown by Kyropoulos technique was characterized using polariscope. The morphology and texture of subgrains from , and orientations were investigated using Synchrotron radiation white‐beam topography technique. The morphology of subgrains was found to be diverse from crystallographic orientation. The relative angles between subgrains are smaller than 1°. The defect structure on a basal‐plane specimen from the lower part of the “shoulder” was examined by X‐ray rocking curve and chemical etching technique. It was found that the defect concentration changes drastically near MCS center. The nature of spatial distribution of MCS and the defect distribution near MCS in a grown boule was discussed in detail.

泡生法生长钛宝石的光学特征

泡生法生长钛宝石的光学特征

A method to strengthen and toughen Sapphire by codoping of Fe/Ti ions

Mechanical properties of titanium and iron co-doped Sapphire crystal are first studied at room temperature Large (ø180 × 280 mm3 in dimension 30 kg in weight) titanium and iron codoped sapphire single crystal is grown by the Kyropoulos technique It is shown that the fracture strength and surface hardness and fracture toughness of as-grown crystals are significantly improved and the visible-infrared optical property is not adversely affected by titanium and iron codoping and certain heat treatment. The Fe3+ in the doped Fe2O3 palys a role of substituting Al3+, leading to an in creased internal stress in the crystal. And the Ti4+ in the doped TiO2 crystallizes the second phase needle crystal and brings in a toughening effect through certain heat treatment. As a consequence, the mechanical properties of as-grown sapphire are improved at room temperature. The present work has the realistic significance for developing the sapphires of excellent mechanical properties.

Study on Properties of Ti:sapphire Crystals Doped Carbon Grown by the Kyropoulos Technique(KY)

Ti:sapphire crystal is of great value in the domain of modern science and technology application. But growth of large Ti:sapphire crystals with a homogeneous titanium distribution and good optical quality is still a challenge. Carbon-doped Ti:sapphire crystal was grown by the Kyropoulos technique. The present work shows that by the utilization of KY growth technology, it is possible to grow carbon-doped Ti:sapphre, with 180 mm in diameter and 30 kg in weight, without macroscopic defects such as cracking. As-grown large crystals show high chemical homogeneities and the figure of merit is above 200, The study has the important practical significance of grown large Ti:Sapphire crystal with low infrared absorption loss and high figure of merit.

Growth, Morphology and Optical Properties of γ-BiB3O6Single Crystals

High quality γ-BiB3O6 single crystals up to 16 × 18 × 32 mm3 in size were grown by the Kyropoulos technique. Indexes of the faces for as grown γ-BiB3O6 single crystals were determined, and transmission spectra were recorded in polarized light. The band gap was found to be Eg = 3.982, 3.968, and 4.008 eV at 300 K for E∥a, b, and c, respectively. Eg decreases linearly versus temperature with a dEg/dT = 0.00127 eV/deg rate for E∥a as temperature grows from 80 to 300 K. Photoluminescence in the broad 2.5 eV band, which is excited in a band near the fundamental absorption edge and quenches completely at 250 K, is associated with self-trapped excitons.

Ti-Doped Sapphire (Al2O3) Single Crystals Grown by the Kyropoulos Technique and Optical Characterizations

Transparent high optical quality and large Ti-sapphire (Ti3+-doped Al2O3) single crystals have been grown by the Kyropoulos technique (KT) for optical amplification. The present work shows that by the utilization of KT growth technology and the optimization of the growth conditions it is possible to grow Ti-doped Al2O3, 100 mm in diameter and 5 kg in weight. We have demonstrated that large Ti(0.25 atom %)-doped Al2O3 crystals show high chemical homogeneities and good optical properties and amplify the energy without any special annealing. Ti-doped sapphire crystals are for high power laser applications and particularly for the shortest pulses ever produced from a laser oscillator.

Modified Kyropoulos法によるKTN単結晶作成—るつぼ回転効果—

Modified Kyropoulos法によるKTN単結晶作成—るつぼ回転効果—

Use of numerical simulation for growing high-quality sapphire crystals by the Kyropoulos method

In the present work, an advanced numerical model is suggested to analyze heat transfer and flow pattern in sapphire crystal growth by the Kyropoulos technique. The new approach accounts for radiative heat exchange in the crystal and convection in the melt, and provides prediction of the crystallization front shape. The model allowed the analysis of several growth setup designs and selection of an optimal configuration. The numerical predictions performed with the CGSim software (www.semitech.us) agree well with available experimental data obtained in optimized crystal growth process reported for the first time.

Numerical analysis of sapphire crystal growth by the Kyropoulos technique

A numerical model has been suggested to analyze processes occurring during sapphire crystal growth by the Kyropoulos technique. The model accounts for the radiative heat exchange in the crystal and melt convection together with the crystallization front formation. The theoretical predictions agree well with available experimental data.

Single crystals of the heavy fermion system CeCu2Si2 grown from the primary solidificationfield

A systematic investigation of the ternary phase diagram of Ce-Cu-Si todetermine the primary solidification area of the heavy fermion system CeCu2Si2 is presented. We examine the liquidus surface bydifferential scanningcalorimetric analysis using a special crucible system. Crystalgrowth experiments are performed from a levitated melt usingthe Nacken Kyropoulos technique. The starting compositions arechosen within the primary solidification area. We obtain highquality single crystals of CeCu2Si2 withdimensions up to 7 mm.

Crystal growth of CeCu 2Si 2 from the primary crystallisation field

We investigate the ternary phase diagram of the Ce–Cu–Si system. From DSC measurements we analyse the liquidus surface which leads together with metallographic studies to the determination of the primary crystallisation field of CeCu 2Si 2. Growth experiments using the Nacken Kyropoulos technique in combination with a levitating melt start with different compositions within and outside the primary solidification field. The comparison of these growth experiments with our results of the phase diagram leads to an understanding of the growth morphology and the growth process of CeCu 2Si 2. Large single grain CeCu 2Si 2 crystals with dimensions up to 7 mm can be grown from a melt of the primary solidification field. First measurements using these single crystals will be reported.