Deposition of mechanically hard amorphous carbon nitride films from decomposition of BrCN. Effects of substrate cooling and pulsed rf-bias voltage

Mechanically hard amorphous carbon nitride films were formed by applying a combination of radio frequency (RF) bias voltage to the substrate and the chemical vapor deposition process using the decomposition reaction of BrCN with the microwave discharge flow of Ar. Cooling water was circulated inside the substrate stage. The maximum hardness was (17 ± 1) GPa for the film prepared under the negative RF bias voltage, −V_RF, of 30 V. This hardness was nearly twice that of the film prepared without cooling, suggesting that substrate cooling was effective for suppressing the relaxation of the internal stress of the film due to the temperature rise during the application of the RF bias voltage. Under the continuous operation of the RF bias voltage, films cannot be formed for −V_RF > 40 V because of the sputtering by the bombardment of energetic Ar⁺. Then, the RF bias voltage was applied with a pulsed operation. By using this operation films were prepared in the range of −V_RF = 40-100 V. The hardness, (36 ± 10) GPa, was obtained for the film obtained under the conditions of −V_RF = 100 V, the pulse period of 1000 s, and the pulse-on time of 800 s. The observed hardness scattered largely for the different observation points within this film; a single observation point in that film showed the maximum hardness of 46 GPa. According to the IR spectra of the films, the three-dimensional C-N network structure was developed.     

Anomalous anisotropic deformations of As2S3 flakes induced by linearly-polarized bandgap illumination

Semi-free As₂S₃ flakes undergo visible-scale anisotropic deformations when exposed to linearly-polarized bandgap illumination. We investigate the behavior and also those in amorphous Se, GeS₂, AgAsS₂, and crystalline As₂S₃. These results suggest that the deformation occurs through photo-induced birefringence, photo-induced fluidity, and optical force.     

Raman scattering,luminescence, and absorption edge under hydrostatic pressures of layered BiI3 and SbI3

Raman scattering from BiI₃ and SbI₃ crystals has been studied at hydrostatic pressures up to 2 GPa. The wavenumbers monotonically increased with pressure for all modes in BiI₃. Although both crystals belong to the same space group, the pressure coefficients of SbI₃ were significantly different from those of BiI₃. At pressure P₀ = 0.92 ± 0.01 GPa, the pressure coefficients of all modes changed. Above P₀, all modes in SbI₃ had positive pressure coefficients as they have in BiI₃. By comparing this unusual behavior of the Raman lines in SbI₃ around P₀ with the results in BiI₃ and comparing the two lattice structures, we suggest that the type of bonding of SbI₃ changes to become more ionic and hence more similar to the bonding of BiI₃. This change in structure is supported by changes in the bandwidth of the self‐trapped exciton (STE) luminescence and the slope of the absorption edge photon energy versus pressure. Copyright © 2007 John Wiley & Sons, Ltd.     

Ca-doping effects on N-type ferrimagnetism of NdVO3

Ca²⁺-doping effects were studied on the N-type ferrimagnet of NdVO₃. The chemical pressures by Ca²⁺-doping induced lowering of ferrimagnetic transition temperature T_c and compensation temperature θ_c, resulting in the phase transition from N- to P-type ferrimagnetic phase. In the N-phase, spontaneous magnetization M_sp becomes zero at finite temperature θ_c and in the P-phase, M_sp is positive in whole temperature range. It was revealed that NdVO₃ and Ca_0.1Nd_0.9VO₃ located in the N-phase and Ca_0.2Nd_0.8VO₃ in the P-phase. This N→P transition by the chemical pressure was discussed by the intra- and inter-sublattice exchange integrals estimated from the molecular field approximation.     

Application of time series analysis and modern control theory to the cement plant

Cement plant process is full of internal noise sources and feedback loops. Therefore, statistical approach is required to understand its dynamic characteristics. Time series analysis has been applied to some important subprocesses of a cement plant process. These are the vertical mill process, calcining process and clinker cooling process. Based on the AR models of these, a set of optimum controllers have been designed by modern control theory. Successful results of application are reported in this paper. A method of determining optimal production level is also discussed.     

High-performance liquid chromatographic determination of nickel,copper and zinc as their tetraphenylporphine chelates

Nickel(II), copper(II) and zinc(II) ions are extracted from an aqueous solution into carbon tetrachloride as their diethyldithiocarbamate (DDC) chelates. The extract, after removal of the solvent, is treated with meso-tetraphenylporphine (TPP) in benzyl alcohol at 140°C for 60 min. Quantitative conversion of the DDC chelate to the TPP chelate is obtained over the range 0.25–4.5 μg of each metal by use of 3 μgmol of TPP. The reaction mixture is analysed by reversed-phase high-performance liquid chromatography with spectrophotometric detection at 412 nm. Simultaneous determination of Cu and Zn in NBS bovine liver is possible by this procedure.     

Recent Advances in Holey Fibers and Their Applications

Transmission loss of holey fiber is found to depend on its structure, and to be caused by Rayleigh scattering at glass surface. Under this loss dependence, most promising is optical wiring application, for which fiber designs to realize bend-insensitivity and single-modedness are presented.     

Toward bioluminescence in the near-infrared region: Tuning the emission wavelength of firefly luciferin analogues by allyl substitution

The synthesis and bioluminescence of allyl-substituted luciferin derivatives as substrates for firefly luciferase are reported. The allylation of luciferins induced bathochromic shift (15–40?nm) of the bioluminescence emission. Upon combination with other chemical modifications for bioluminescence wavelength tuning, novel red emitting luciferin analogues were obtained with emission maxima at 685 and 690?nm.