Jun Suda

Spiral Crystal Growth of Potassium Dichromate in Gelatin.

Huge spiral crystals of potassium dichromate (K 2 Cr 2 O 7 ) have been found to grow three-dimensionally in a gelatin medium when gelatin containing K 2 Cr 2 O 7 was dried slowly in a test tube at a low temperature. These spirals were all right-handed, and their widths, axial pitches and lengths were 2–3 mm, 5–6 mm and 20–25 mm, respectively. When the gelatin concentration in the medium was decreased, ordinary platelike crystals were observed to grow, instead of the spiral crystals. To the best of our knowledge, inorganic compounds such as K 2 Cr 2 O 7 have so far not been reported to form such huge spiral crystals. It is conjectured that collagen molecules, which compose the gelatin medium and have right-handed triple helix structure lead to the growth of spiral crystals.

Lattice dynamics and temperature dependence of the linewidth of the first-order Raman spectra for sintered hexagonal GeO2 crystalline

The first-order Raman spectra of internal A1 and external modes in sintered hexagonal GeO 2 crystalline were measured in the temperature range of 293–873 K and the linewidths at these temperatures were obtained. The temperature dependence of the linewidths was analyzed using the phonon dispersion curves calculated on the basis of a rigid-ion model, and the results showed that it was caused approximately by the cubic anharmonic term in the crystal potential energy.

Temperature Dependence of the Ag+Bg-Mode of Raman Shift for CaWO 4 Crystal

The first-order Raman frequency shifts of the A g (2) + B g (2) mode in a CaWO 4 crystal were measured in the temperature range of 77∼771 K. The frequency shift for this mode changes very slowly with increasing temperature. The temperature dependence of the frequency shift of the A g (2) + B g (2) mode was analyzed using the lattice dynamical perturbative treatment. We found that the quartic anharmonic term of the first-order perturbation, as well as the cubic term of the second-order one, and thermal expansion contribute to the temperature dependence of the frequency shift of the A g (2) + B g (2) mode in a CaWO 4 crystal.

Temperature Dependence of the Linewidth of the First-Order Raman Spectra for Aragonite Crystal

The first-order Raman spectra of A 1 g and B 1 g mode in aragonite crystal were measured in the temperature range of 4.4∼630 K and the linewidths at these temperature were obtained. The temperature dependence of the linewidths was analyzed by the phonon dispersion curves based on the Born-von Karman model, and the results showed that it was caused approximately by the cubic anharmonic term in crystal potential energy.

The First-Order Raman Spectra and Lattice Dynamics for YAlO3 Crystal

The phonon-dispersion curves of the YAlO 3 crystal are calculated on the basis of a rigid-ion model using the measured frequency values by Raman and infrared polarized spectroscopy at room temperat...

Micro-Raman imaging on 4H-SiC in contact with the electrode at room temperature

Raman images (30μm×30μm×180μm) of a bulk 4H-SiC wafer in contact with a Ni/Au electrode film in 100nm/200nm thick were measured with Micro-Raman spectroscopy at room temperature. As the imaging area approached the interface between the SiC and electrode, the center frequency of the E2(TO) mode (778cm-1) immediately declined; in the Raman imaging, relative distribution of compressive residual stress around residual tensile stress, and linewidth were broadened due to crystal distortion. For LOPC (LO-phonon-plasmon-coupled) mode (970cm-1), center frequency showed variation right next to the interface, while linewidth decreased slowly as the imaging area approached the interface. We evaluated the temperature dependence of the line broadening and the center frequency of the LOPC mode in 4H-SiC in a high-temperature region. Free carrier concentration increased with temperature, and remained almost constant in the center frequency after impurities were ionized completely.

Investigation of mode assignment on YVO4 crystal in high temperature region by polarized Raman spectroscopy and first principles calculations

Polarized Raman spectra for 11 modes in the YVO4 crystal were measured in the temperature range from room temperature to 473K, and the mode assignment on Raman modes was analyzed using the first-principles calculations. We found that the calculated frequency values are in good agreement with the experimental ones. The large difference of the temperature line broadening between two peaks (380cm-1 and 891cm-1) of A1g mode has been reported and it is thought to be due to band gap effect in PDOS.