The diffusion mechanism of tin into glass was investigated using a lab-scale float apparatus, in order to determine the reasons for the characteristic tin penetration profile of float glass. Tin penetration profiles of glass samples heated at various temperatures, times and atmospheres were measured by means of SIMS. The tin enriched inner layer, that is characteristic of the tin penetration profile of float glass, was seen to be formed by heating at more than 800oC. It was found that the depth of the tin enriched inner layer was proportional to the holding time at the maximum temperature during the heat treatment, and was inversely proportional to the Fe3+ concentration in the glass. It was also proven that the tin enriched inner layer was formed by penetration of hydrogen from the atmosphere through the molten tin into the glass. These facts indicate that the reaction between hydrogen and Fe3+ is involved in the formation of the tin enriched inner layer. Consequently, it has been proposed that the mechanism of formation of the tin enriched inner layer is governed by two redox reactions and the diffusion behavior of both Sn2+ and Sn4+. Namely, one of these two redox reactions is the reduction of Fe3+ to Fe2+ due to hydrogen, resulting in the formation of a reduced surface layer. Another is the oxidation of Sn2+ to Sn4+ due to Fe3+ in the glass. These analytical results leading to a successful control of tin penetration into glass during the float process are discussed in detail.
Near-UV emitting diodes composed of wide band gap oxide semiconductors, p-SrCu2O2 and n-ZnO heterojunctions, were fabricated and their emission properties were investigated. Single crystal ITO thin films with very flat surfaces were grown using PLD on YSZ substrates, and ZnO films were heteroepitaxially grown on the ITO surfaces. p-SrCu2O2(112) was preferentially grown on ZnO(0001) at 350oC, while the preferential plane was changed into the (100) when the temperature was increased to 600oC. This device exhibited rectifying I-V characteristics inherent to p-n junction whose turn-on voltage was about 3 V. A relatively sharp electro-luminescence band centered at 382 nm was generated by applying the forward bias voltage larger than the turn-on voltage of 3 V. The red shift in the EL peak was noticed from that of photo-luminescence (377 nm), which was most likely due to the difference in the excited state density between the emission processes. The EL band is attributed to transition in ZnO, probably to that associated with electron-hole plasma. UV-LED performance characteristics such as threshold current and conversion efficiency was improved with higher SrCu2O2 deposition temperatures.
Barrier height of self-assembled monolayers (SAMs) on Au(111) was measured using scanning tunneling microscopy (STM) with a vertical modulation. We obtained nanometer scale STM images of alkanethiol SAMs, and binary component SAM films fabricated by an implantation technique. Local barrier height on the alkanethiol SAM at the depressions and the domain boundaries is larger than that on the domains where the molecular lattice is visible, probably due to the molecular density or orientation. A molecular resolution contrast was obtained at a conjugated molecule embedded in the alkanethiol SAM, reflecting the difference in the molecular species. We found that the tip-sample interaction force affects the barrier height measurements, especially when the tunneling gap is small, e.g., on nonanethiol SAM at the tunneling resistance smaller than 50 GΩ.
A compact high-resolution RBS system consisting of a 90o sector magnetic spectrometer (radius 200 mm), a quadrupole lens, an electrostatic deflector and a one dimensional position sensitive detector (length 100 mm) has been developed. The measured energy resolution of the spectrometer is 0.11% of the analyzing energy at an acceptance angle of 0.3 msr including the energy spread of the incident ion beam. Some observations using this new system are presented.
We investigated ions and X-rays generated from a Cu target by irradiation of a femtosecond laser pulse at power densities above 1015 W/cm2. The kinetic energy of positive ions was measured by a charge collector. The time-of-flight spectra showed multi-peaked structures. The ion energy of faster peak was estimated to be 4.6 keV at power density of 1×1017 W/cm2. This ion energy increased with an increase in the laser energy. The ion energy of slower peak was estimated to be about 20 eV and independent of the laser energy. Generated X-rays were detected as hard X-rays in the range of 3-30 keV and as CuKα line diffracted from Si(111). Both intensities increased with an increase in the laser energy.
Electron emission spectra caused by thermal collisions of He* (23S) metastable atoms with Ni(100)c(2×2)-CO and Ni(111)c(4×2)-CO were measured to probe the local electron distribution. Our data showed that the 4σ- and 5σ-derived states of CO at hollow sites on Ni(111) are strongly modified in space by mixing with each other, where considerable charge transfer occurs from the C atom to the O atom in the 5σ-derived state and in the opposite way in the 4σ-derived state. In contrast, such a heavy charge redistribution was not seen in the case of terminal CO on Ni(100). These findings were in good accordance with the crystal orbital overlap population obtained by density functional theory within the generalized gradient approximation.
The electronic structure of a clean and H-adsorbed HfC(111) surface have been studied by angle-resolved photoemission spectroscopy and Discrete-Variational Xα molecular orbital calculation. A sharp peak in normal-emission spectra of the clean surface is observed at just below the Fermi level, and the peak is ascribed to the emission from a surface state composed of 5d orbitals of surface Hf atoms. Hydrogen adsorbs dissociatively on the HfC(111) surface forming a (1×1) overlayer at the saturation coverage. H-induced bands are observed at 6-7 eV and around the Fermi level. The calculation for the Hf13C13H3 cluster shows that these bands should be ascribed to a H 1s-Hf 5d bonding state and an extrinsic surface state composed of Hf 5d orbitals formed through the modification of the surface potential by H-adsorption, respectively.
Relationship between surface structure of hot rolled steel sheets and their galvannealing behavior has been examined using SEM, EPMA and SIMS. Si and P as oxides are enriched at the interface between oxide layers and steel substrates of the hot rolled steel sheets. Quantity of the enriched elements increases as a function of thickness of the oxide layer, namely oxidation time. Some Si oxides remained on the surface, although most of the oxide layer had been removed by dipping them in HCl with a pickling inhibitor. Surface grains of steels as well as the oxide layers were removed in HCl without the pickling inhibitor, but the surface is covered with phosphide of P segregated to the grain boundaries. The segregated P seems to suppress the successive dissolution of the grains. Thick areas of about 0.5 mm diameter have been formed in the coating of the hot rolled steel pickled in HCl with the inhibitor, although the uniform coatings have been formed in the case of the hot rolled steel pickled in HCl without the inhibitor. The thick areas are caused by the anomalous alloying of Zn and Fe present near the Si oxide left on the steel surface.
Composition, surface morphology and phase structure of Sn-Ag-Cu ternary alloys electrodeposited from pyrophosphate-Iodide bath under the galvanostatic conditions were examined. Contents of Ag and Cu in the deposits decreased with increasing current density. There was correlations between surface morphology of the deposits and their compositions. Composition-phase diagram of the electrodeposits corresponded to Sn-Ag-Cu ternary alloy phase diagram in the composition range with higher content of Sn.