Studies on the morphology transition of micro-crystal growth in polymer films in high vacuum and strong electrostatic field

The morphology of films of isotactic polypropylene poly (3-dodecylthiophene) and iPP/P3DDT blend formed in electrostatic fields has been investigated by using scanning electron microscope. The experiment results show that the micro-crystal morphology of polymer films was strongly dependent on electrostatic fields. It was found that the effect of the electrostatic field led to the formation of dendrite crystals aligned in the field direction, and some branches of P3DDT ruptured. However, the micro-crystals in these films grew into spherulites without electrostatic field,and have no crystal orientation.

Crystal growth and TG-DTA properties of K(2)Ln(NO3)(5).2H(2)O (Ln = La, Ce, Pr, Nd, Sm)

Single crystals of KLnN(Ln=La, Ce, Pr, Nd, Sm) can be grown in water solution with pH approximate to 1 similar to 2 at about 40 degrees C. Crystals of KLnN (Ln=La, Ce, Pr, Nd) are orthorhombic with space group Fdd2. KPrN crystal was grwon and its crystal structure was determined for the first time. The KPrN crystal parameters obtained by the direct method are as follows: a=21.411(3) Angstrom, b=11.2210(10)Angstrom, c=12.208(2) Angstrom, Z=6, R=0.0240. The TG-DTA curves of KLnN(Ln=La,Ce, Pr, Nd, Sm) demonstrate that the processes of dehydration, melt, irreversible phase transition and decomposition of NO3- take place in sequence with the temperature increasing(except KCN). There are three steps in the decomposition of NO3- in KLnN(Ln=La, Nd, Sm) while two steps in KLnN (Ln=Ce, Pr). K(2)Ln(NO3)(5). 2H(2)O are formed at about 225 degrees C by the reaction of the starting materials of KNO3 and Ln(NO3)(3). nH(2)O.

Single crystal growth and spectroscopic properties of KZnF3:Eu3+

Single crystal of KZnF3 : Eu3+ has been grown by means of Bridgman-Stockbarger technique in Ar atmosphere, The emission and excitation spectra of europium ion were measured, The results show that a small amount of Eu2+ exists in the crystal, The existence of Eu2+ ions was also confirmed by ESR data, The valence change of Eu ions during the crystal growth is due to unequivalent substitution of Eu3+ ions for the lattice ions. The sites possibly occupied by Eu ions in this crystal were also discussed.

Growth and spectroscopic characteristics of Yb : LPS single crystal

For the first time, a high optical quality Yb3+-doped lutetium pyrosilicate laser crystal Lu2Si2O7 (LPS) was grown by the Czochralski (Cz) method. The segregation coefficient of ytterbium ion in Yb:LPS crystal detected by the inductively coupled plasma atomic emission spectrometer (TCP-AES) method is equal to 0.847. X-ray powder diffraction result confirms the C2/m phase monoclinic space group of the grown crystal and the peaks corresponding to different phases were indexed. The absorption and fluorescence spectra, as well as fluorescence decay lifetime of Yb3+ ion in LPS have been investigated. The absorption and fluorescence cross-sections of the transitions F-2(7/2) <-> F-2(5/2) of Yb3+ ion in LPS crystal have been determined. The advantages of the Yb:LPS crystal including high crystal quality, quasi-four-level laser operating scheme, high absorption cross-sections (1.33 x 10(-2) cm(2)) and particularly broad emission bandwidth (similar to 62 nm) indicated that the Yb:LPS crystal seemed to be a promising candidate used as compact, efficient thin chip lasers when LD is pumped at 940 and 980 nm due to its low-symmetry monoclinic structure and single crystallographic site. (c) 2007 Elsevier B.V. All rights reserved.

Growth and spectral properties of Yb : FAP single crystal

In this paper, single crystal of ytterbium (Yb) doped Ca-5(PO4)(3)F (FAP) has been grown along the c-axis by using the Czochralski method. The segregation coefficients of Yb3+ in the Yb:FAP crystal has been determined by ICP-AES method. The absorption spectrum, fluorescence spectrum and fluorescence lifetime of the Yb:FAP crystal has been also measured at room temperature. In the absorption spectra, there are two absorption bands at 904 and 982 nm, respectively, which are suitable for InGaAs diode laser pumping. The absorption cross-section (sigma(abs)) is 5.117 x 10(-20) cm(2) with an FWHM of 4 nm at 982 nm. The emission cross-section is (sigma(em)) 3.678 x 10(-20) cm(2) at 1042 nm. Favorable values of the absorption cross-section at about 982 nm are promising candidates for laser diode (LD) pumping. (c) 2005 Elsevier B.V. All rights reserved.

Growth and spectral properties of Yb,Tm:YAG crystal

The YAG crystal codoped with Yb3+ and Tm3+ has been grown by Czochralski (Cz) method. The crystal structure of the crystal has been determined by X-ray diffraction analysis. The absorption and emission spectra of Yb,Tm:YAG crystal at room temperature have also been studied. The emission cross-sections have been calculated by Fuechtbauer-Ladenburg formula and reciprocity method. (C) 2007 Elsevier B.V. All rights reserved.

Growth of highly sensitive thermoluminescent crystal alpha-Al2O3 : C by the temperature gradient technique

In this work, an alpha-Al2O3:C crystal with highly sensitive thermoluminescence was directly grown by the temperature gradient technique (TGT) using Al2O3 and graphite powders as raw materials. The optical and luminescent properties and the dosimetric characteristics of the crystal were investigated. An as-grown alpha-Al2O3:C crystal shows a single glow peak at 462 K and a blue emission peak at 415 nm. The thermoluminescence (TL) response of the crystal shows a linear-sublinear-saturation characteristic. In the dose range from 5 x 10(-6) to 10Gy, the alpha-Al2O3:C crystal shows excellent linearity, and saturation was observed at about 30Gy. The sensitivity of the crystal decreases as the heating rate increases. (c) 2008 Elsevier B.V. All rights reserved.

Growth and annealing properties of Mg0.4Al2.4O4 crystal

Mg0.4Al2.4O4 single crystals with good optical quality were successfully grown by the Czochralski method. The transmission spectrum indicated that the absorption edge of the crystal was at 220nm, while no apparent absorption peaks were found. The X-ray diffraction and DSC curve analysis showed that Mg0.4Al2.4O4 crystal was stable at room temperature. While after annealing in the air and hydrogen atmosphere at about 1200 degrees C,Mg0.4Al2.4O4 decomposed into Al2O3 and (MgO)(0.4)(Al2O3)(x) (0.4 < x < 1.2). The reaction mainly occurred on the crystal surface, barely inside. (C) 2008 Elsevier B.V. All rights reserved.

Growth of ZnO single crystal by chemical vapor transport method

ZnO crystals were grown by CVT method in closed quartz tube under seeded condition. Carbon was used as a transport agent to enhance the chemical transport of ZnO in the growth process. ZnO single crystals were grown by using GaN/sapphire and GaN/Si wafer as seeds. The property and crystal quality of the ZnO single crystals was studied by photoluminescence spectroscopy and X-ray diffraction technique.

Growth of high quality semi-insulating InP single crystal by suppression of compensation defects

Deep level defects in as-grown and annealed SI-InP samples were investigated by thermally stimulated current spectroscopy. Correlations between electrical property, compensation ratio, thermal stability and deep defect concentration in SI-InP were revealed. An optimized crystal growth condition for high quality SI-InP was demonstrated based on the experimental results.

Effect of in situ thermal treatment during growth on crystal quality of GaN epilayer grown on sapphire substrate by MOVPE

GaN epilayers on sapphire substrate grown by metalorganic vapor-phase epitaxy (MOVPE) in a horizontal-type low-pressure two-channel reactor were investigated. Samples were characterized by X-ray diffraction (XRD), Raman scattering, atomic force microscopy (AFM) and photoluminescence (PL) measurements. The influence of the temperature changes between low temperature (LT) deposited GaN buffer and high temperature (WT) grown GaN epilayer on crystal quality of epilayer was extensively studied. The effect of in situ thermal annealing during the growth on improving the GaN layer crystal quality was demonstrated and the possible mechanism involved in such a growth process was discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

Growth of ZnO single crystal by chemical vapor transport method

ZnO crystals were grown by CVT method in closed quartz tube under seeded condition. Carbon was used as a transport agent to enhance the chemical transport of ZnO in the growth process. ZnO single crystals were grown by using GaN/sapphire and GaN/Si wafer as seeds. The property and crystal quality of the ZnO single crystals was studied by photoluminescence spectroscopy and X-ray diffraction technique.

Growth of high quality semi-insulating InP single crystal by suppression of compensation defects

Deep level defects in as-grown and annealed SI-InP samples were investigated by thermally stimulated current spectroscopy. Correlations between electrical property, compensation ratio, thermal stability and deep defect concentration in SI-InP were revealed. An optimized crystal growth condition for high quality SI-InP was demonstrated based on the experimental results.