Strontium tetraborate (SrB4O7) single crystal has been successfully grown by the CZ method, and it was revealed that this crystal has higher Rayleigh surface wave on  plane, compared with other piezoelectric materials.
Near-stoichiometric lithium niobate(SLN) single crystal for holographic application was grown by the resistive-heating TSSG method. Fe. Tb atoms were doped into the SLN crystals. The segregation co-efficient of Fe and Tb was 0.25, 0.5, respectively. Two-color nonvolatile holographic recording has been demonstrated with the grown single crystals.
Near-stoichiometric LiTaO_3 (SLT) single crystals were grown from Li-rich solutions by the double-crucible Czochralski (DCCZ) method using an automatic coarse-grained SLT powder supply system. The influence of supply on compositional uniformity of the grown SLT crystals was investigated and compositional uniformity of SLT crystals was estimated by the measurement of Curie temperature.
Growth of langasite single crystal of 4 inch in diameter along Y54 direction by CZ method was investigated. The structure of a hot zone, pulling rate and rotation rate were optimized, and some crystals without a macro defect were obtained. The homogeneity of the crystals was evaluated. The distribution of sound velocity between lots is about 120 ppm in standard deviation.
A 2-in single crystal of La_3Ga_5SiO_<14> (LGS) was successfully grown by the vertical Bridgman technique equipped with accelerated crucible rotation technique (ACRT). The selected growth axis was <101^^-1> which is an effective orientation for slicing commercial wafers. The furnace has three heatingzones where the temperature gradient was optimized for the growth. The secondary phase which is commonly observed along <101^^-0> was reduced by choosing the appropriate acceleration rate.
The potassium niobate (KNbO_3) crystal was grown in air or nitrogen gas by TSFZ method. As a result, when grown in air, the melt part was not stable and we could not zone-pass. When in nitrogen gas, the absorption of infrared rays was improved and by zone-passing the blue colored polycrystal was grown. By powder X-ray diffraction method the polycrystal was orthorhombic KNbO_3
LBO (Li_2B_4O_7) is considered to be one of the useful materials for neutron detection because it contains Li and B, which possess large neutron capture cross-section isotopes. In the present study we report crystal growth of Cu doped LBO grown by Bridgman method and characterized on their luminescent properties.
Nd doped Li_2B4O_7 crystals have been successfully grown by the Bridgman Stockbager technique. The transmittance, crystal density and Xray diffraction were measured. The growth and characterization of Nd doped Li_2B4O_7 crystals will be discussed.
Rutile single crystals inclined at 48°to the c-axis were successfully prepared at a high growth rate of 40 mm/h by the floating zone method. A small crystal-diameter of about 3 mm was effective to suppress the formation of low-angle grain boundaries under an oxygen partial pressure of about 10^3 Pa. At a growth rate of 60 mm/h, any grown crystals did not contain low-angle grain boundaries but incorporated a number of bubbles without regard to oxygen partial pressures between 10^2 and 10^4 Pa.
Abstract: The fiber-optic thermometer probe using chromium doped spinel crystal. MgAl_2O_4: Cr^<3+>, and ruby crystal. Al_2O_4 Cr^<3+> are fabricated. The lifetime of spinel and ruby crystal decrease with temperature. Lifetimes and temperature coefficients of the spinel crystals (τ=10 ms. -37μs/K) were about 3 times larger than that of the ruby crystals (τ=4ms, -10μs/K).
RNbO_4 (R: Rare-earth) crystals have ferroelastic properties. Hysteresis loop in stress-strain curve was reported on NdNbO_4 Luminescent properties were also reported on Ce or Pr doped YNbO_4 and YTaO_4. RNbO_4 single crystal were grown by Czochralski method and flux method. In this work. RNb04 (R: Gd, Dy, La and Y) single crystals are grown by Floating zone method, and are investigated their growth conditions.
Abstract: CaAl_2O_4:Eu^<2+> phosphor crystals co-doped with auxiliary activators such as Sc, Y, La, Ce, Pr, Nd have been grown by floating zone (FZ) technique. photoluminescence spectrum (PL), time resolved PL and thermally stimulated luminescence (TSL) are evaluated to clarify the long phosphorescence mechanism. Trap depth and the densities of the trapped carriers vary with the auxiliary activator elements.
We have developed a new crystal growth method named as the traveling liquidus-zone method for growing homogeneous mixed crystals. Principle of this method and experimental results on In_<0.3>Gs_<0.7>As crystal growth are reviewed.
REBa_2Cu_3O_x(RE123: RE=Y, Sm ...) superconductive bulk oxides are widely fabricated by melt and growth processes and are known to grow through the peritectic reaction which is controlled by the solute diffusion in liquid. Controlling both the temperature at interface and the liquid composition is, therefore, important to obtain RE123 crystals with better superconducting properties
Dislocations due to lattice misfit suppressed at the interface of heavily B-doped Si seed and lightly B-doped Si crystal in CZ-Si crystal growth when the difference in B concentration in the seed and grown crystal was less than 7×10^<18> atoms/cm^3, corresponding to lattice constant of 2×10-<-4>Å The gradual B concentration distribution was formed at the interface by thermal diffusion of B atoms from the heavily B-doped Si seed during the crystal growth, and the relationship between the distribution and the formation of dislocations due to lattice misfi was investigated.
Some fluoride crystals have cubic structure. Especially, the crystal of calcium fluoride has low refractive index, low dispersion and low solubility of water at room temperature. This crystal is now widely used for window material in ultraviolet region. The latest topics about fluoride crystals will be introduced.
Incongruency of langasite (La_3Ga_5SiO_<14>) melt was studied by quenching melts with various compositions after keeping at certain temperatures and analyzing the resulted phases by energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). Aciculae that are not langasite were observed in quenched samples of both sintered material and single crystal of stoichiometric composition, while the first-formed langasite crystal was precipitated in samples with Ga_2O_3-rich and La_2O_3-poor compositions. This suggests that langasite is peritectic and the precipitation of the aciculae in CZ-growth is probably the cause of abnormal growth and consequent cracks in langasite crystal.
Using different composition melts in Li_2O-Nb_2O_5 system, their density, surace tension and viscosity were measured. The results showed that the density and surface tension varied linearly as a function of temperature and composition. We found a nonlinear increase in viscosity at the congruent and stoichiometric melt compositions when the temperature approached to the liquidus curves. In contrast, the melt close to the eutectic compositions showed a linear change in viscosity with temperature down to the solidification temperatures.
Three-dimensional time-dependent flow of oxide melts in Czochralski system was numerically investigated under a condition of an accelerated crucible rotation technique (ACRT). The effect of double crucible method, which can separate feed material and a growing crystal, was also studies simultaneously to grow long crystals. The calculation clarified that the time-dependent crucible-rotation with acceleration can stabilize the convection of the melt effectively. Moreover, it has been clarified that the double crucible rotation technique can also stabilize convection of the melt due to existence an inner wall.
We have conducted lateral growth by low angle incidence MBE. In this work, we carried out epitaxial lateral growth from ridge structure. The incidence angles were chosen as 12°and 21°in the growth and effect of incidence angle was studied.
We systematically studied the incorporation mechanism of oxygen into MBE-grown AlGaAs-based materials with changing both growth temperature and growth rate of the layers. All the results are explained well with considering that the segregation of oxygen atoms plays very important role in its incorporation.
We found that the lateral oxidation of GaAS/AlAS hetero structures with a Be-doped GaAs layer depended on the amount of Be doping. Be doping increased the oxidation rate over that of undoped layers, and the rate increased with an increase of Be doping. Qualitatively, the results indicated that oxygen ions transport through the through oxidation layer and electrons transport through the GaAs layer.
Lateral p-n junctions at GaAS/AlGaAS heterointerfaces were grown by MBE at various As pressures. We obtained the optimum emission intensity at the As pressure of 2.8×10^<-3> Pa by measuring the electroluminescence from patterned substrate of GaAs (111)A with (100) side planes. The emission was from the (111)A surface and depended on the acceptor level.
We grew Si-doped GaAs on GaAs (111)A substrates by molecular beam epitaxy (MBE) with and without growth interruption . Their electric and optical properties were then studied. The amount of acceptor Si that incorporated into GaAs(111)A layer increased by the interruption growth.
An As adsorption layer on the GaAs(100) substrate was indicated by in situ RHEED measurements during MBE growth at high As pressure. A measured decrease of growth rate suggests that Ga evaporates from As overlayer thus decreasing the amount of Ga reaching growth sites on the GaAs substrate surface.
An AlGaN/GaN heterojunction field effect transistor (HFET) was fabricated using a gas-source molecular beam epitaxy (GSMBE). A higher electron mobility (1200cm^2/Vs) was obtained at RT. A selective area growth (SAG) technique was carried out for the formation of a source and drain contacts. As a result, a high power AlGaN/GaN HFET was demonstrated.
GaN, AlGaN epilayers and GaN/Al_<0.15>Ga_<0.85>N multiple quantum wells (MQWs) were grown on GaN single crystals by molecular beam epitaxy. Low temperature photoluminescence spectra of the GaN/Al_<0.15>Ga_<0.85>N MQW exhibited intense QW-related emission peaks. The variation of QW transition energy versus the well thickness (from 2 ML to 18 ML: 1 ML=2.59Å) indicates the presence of built-in electric field in the wurtzite GaN/ Al_<0.15>Ga_<0.85>N heterostructure.
The growth of GaN epilayers on the N-face of pressure-controlled solution growth (PC-SG) bulk GaN single crystals has been performed by RF-MBE. As a result, it is found that GaN epilayers grown on the N-face using In-doped GaN buffer layers have Ga-polarity. This result suggests that In-doping has the role of reversing the polarity of the GaN epilayers from N- to Ga-polarity.
Microstructure of InN films grown on (0001) sapphire substrates by RF-MBE was observed using transmission electron microscopy. It was confirmed that InN grown directly on sapphire had mainly two types of epitaxial relationship with sapphire. On the other hand, InN grown with nitridation was found to have one epitaxial relationship, but showed grain structure with c-axis orientation distribution at initial growth stage.
TiO_2 has the advantage of low lattice mismatch of just about 2 % with Gubic GaN. We studied cubic GaN grouth on a (001) rutile TiO_2 substrate by ECR-MBE. For the first time, oriented cubic GaN polytype was obtained on the substrate by optimizing growth temperature. Growth orientation of the cubic GaN was found to be <110>.
Polycrystalline GaN layers were grown on a patterning silica glass substrate by ECR'MBE. Photolithography technique and RIE were used for the patterning process. Although improvement of a-axis orientation of GaN was not confirmed by RHEED, a large number of oriented grains lined up at the side of the pattern were observed by SEM.
InN films grown on (0001) sapphire substrate tend to have metastable rotation domains within c-plane due to the latticemismatchbetweenltiNandsapphireandduetothesubstratestructure. Initial growth processes of substrate nitridation and buffer layer deposition are useful and effective way to control the rotation domains.
GaN was grown on the Si (111) substrate using MOCVD. The growth conditions of a buffer layer were investigated at 600-850℃. The optimum buffer layer condition was confirmed. As a result, a homogeneous GaN layer without cracking was obtained.
ErP/InP heterostructure is one of the candidates for realizing new functional high-speed magneto-electronic devices. We have investigated growth morphology of ErP on InP (001) and (111)A. ErP/InP heterostructures were grown by face-down OMVPE. ErP formed islands on each orientation, while island size and height were quite different between two orientations.
We have fabricated Er,O-codoped GaAs/GanP double-heterostructure(DH) light-emitting diodes(LEDs) grown by organometallic vapor phase epitaxy and investigated their optical properties. Under forward bias, the LEDs exhibited radiant Er-related electroluminescence(EL) at around 1.54μm at room temperature. The spectrum was identical to the photoluminescence(PL) spectrum due to an Er-O center. This indicates that the Er-2O center is excited effectively by current injection.
We have successfully obtained InAs quantum dots grown on InGaAsP/InP by droplet hetero-epitaxy and observed room-temperature electroluminescence (EL) due to the InAs dots. Formation of InAs quantum dots has been investigated as a function of TMIn supply time for formation of In droplets.
We have grown n-type GaInP layers on GaAs substrates by organometallic vapor phase epitaxy using H_2S as a dopant source. We have found a decrease in the GaInP lattice constant with an increasing H_2S supply. The lattice constant of GaInP varied from 5.7009 to 5.6318Å for the H_2S supply from 0 to 1.786μmol/min. The In composition depends greatly on the H_2S supply.
Metalorganic chemical vapor deposition of zinc oxide film was performed in a high magnetic field with diethyl zinc and water vapor as starting materials. Reducing in deposition rate, increasing of dendritic crystals were observed.
Er-doped light-emitting Si films grown by solid phase epitaxy have been evaluated by time-resolved photoluminescence (TRPL) and medium-energy coaxial impact-collision ion scattering spectroscopy (ME-CAICISS). It was found that the light emission characteristics correspond to the crystal structure of the films, which were grown on Si(111) substrate and Si(001) substrate.
The dislocation density observation of GaN grown on SiC substrates by the chemical wet etching was carried out. The hot phosphoric acid and molten potassium hydroxide were used for the examination. The dislocation density was estimated by counting the number of etch pits.
In order to clarify the formation mechanism of the empirically known silicon epitaxial film profile, this study evaluates the influence of the gas inlet geometry on the transport phenomena in the horizontal single-wafer epitaxi al reactor, using the numerical calculation based on the transport and epitaxy model.