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Cr-doped (Gd x Y 1− x ) 3 Ga 5 O 12 crystals ( x =0.00, 0.25, 0.50, 0.75 and 1.00) were grown by the micro-pulling-down method and examined for their possible application as red and infrared scintillating detectors in medical field. Although Cr:(Gd 0.75 Y 0.25 ) 3 Ga 5 O 12 and Cr:Gd 3 Ga 5 O 12 had similar X-ray diffraction patterns, other samples showed some change in lattice constant. All the crystals had broad emission bands in the red and infrared region when excited by either 450 nm photons or X rays. These bands were associated with 4 T 2 →A 2 transitions. Moreover, redshift of the emission-peak wavelengths ( 4 T 2 → 4 A 2 ) and absorption peaks ( 4 A 2 → 4 T 1 and 4 T 2 ) was observed with increase of Gd content ( x ) in Cr-doped (Gd x Y 1 −x ) 3 Ga 5 O 12 due to the change of the crystal fields. The crystals had scintillation emissions in the wavelength region suitable for the real time dose monitoring in radiation therapy. [ABSTRACT FROM AUTHOR]

Abstract: Nd and Yb doped CaYAlO4 crystals have been grown by the micro-pulling down method. The segregation coefficient along the growth direction and the radial dopant distribution were measured by using electron probe micro-analysis (EPMA). The X-ray induced luminescence spectra in the spectral range from 300 to 1500nm were measured: Nd and Yb doped CaYAlO4 showed intense peaks at 990 and 1045nm, respectively. These crystals would be promising materials for near infrared emission scintillators. [Copyright &y& Elsevier]

Abstract: To improve crystal quality of InN, an in-situ cyclic rapid pulse annealing during growth was carried out using infrared-lamp-heated molecular beam epitaxy. A cycle of 4min growth of InN at 400°C and 3s pulse annealing at a higher temperature was repeated 15 times on AlN on Si substrate. Annealing temperatures were 550, 590, 620, and 660°C. The back of Si was directly heated by lamp irradiation through a quartz rod. A total InN film thickness was about 200nm. With increasing annealing temperature up to 620°C, crystal grain size by scanning electron microscope showed a tendency to increase, while widths of X-ray diffraction rocking curve of (0002) reflection and E2 (high) mode peak of Raman scattering spectra decreased. A peak of In (101) appeared in X-ray diffraction by annealing higher than 590°C, and In droplets were found on the surface by annealing at 660°C. [Copyright &y& Elsevier]

Abstract: We have carried out a numerical simulation of the hydrothermal process for growing bulk single crystals of ZnO using SC/Tetra as the computational fluid dynamics software. The autoclave is assumed to be axisymmetric. The heat transfer by natural convection is calculated in order to study the effects of the variations in fluid properties. It has been found that the effect of the variations in heat capacity and viscosity is large. The temperature difference and flow rate between the raw-material zone and the crystal-growth zone are also discussed from the viewpoint of the transport phenomena in a crystal-growth process. [Copyright &y& Elsevier]

This paper describes studies of the polarity of InN layers grown by radio-frequency plasma-assisted molecular-beam epitaxy. The InN layers in this study were grown on a variety of substrates: (0 0 0 1) sapphire substrates; (0 0 0 1) Ga-face and (0 0 0 &1macr;) N-face free-standing GaN substrates, and (0 0 0 1) Si-face and (0 0 0 &1macr;) C-face 6H-SiC substrates. It was found that the InN layers grown on the sapphire substrates had N-polarity. Furthermore, the growth temperature for successful growth of InN was strongly dependent on the substrate polarity: InN could be grown at 550°C on N-face GaN and C-face SiC substrates, while InN growth was only realized at a decreased temperature of 450°C on Ga-face GaN and Si-face SiC substrates. The polarity of the InN layers grown on the SiC substrates was further examined by etching the InN surface using KOH solution. The InN layers grown on Si-face and C-face SiC substrates had In-polarity and N-polarity, respectively. As a result, InN with N-polarity can be grown at higher temperature than InN with In-polarity, this can be explained by the different bonding configuration of the surface N atoms with the underlying In atoms for the two growth processes with In-polarity and N-polarity. [Copyright &y& Elsevier]

Abstract: Some pyrosilicate scintillators such as Ce:Gd2Si2O7 and Ce:Lu2Si2O7 have a good light output, and especially Ce:(Gd,La)2Si2O7 has an excellent light output of over 36,000ph/MeV. In order to search novel scintilators, we have developed a pyrogermanate-based scintillation material (Ce0.01,Gd0.90,La0.09)2Ge2O7 using the floating zone method. Although the light output was decreased due to quenching, 5d–4f transition of Ce3+ was observed around 480nm in photo- and radio-luminescence spectra. This emission wavelength was longer than that of (Ce0.01,Gd0.90,La0.09)2Si2O7 with an emission wavelength of 390nm. [Copyright &y& Elsevier]