A review of the random magnetic impurity model, introduced in the context of the quantum Hall effect, is presented. It models an electron moving in a plane and coupled to random Aharonov-Bohm vortices carrying a fraction of the flux quantum. Recent results on its perturbative expansion are given. In particular, some peculiar families of integrals turn out to be related to the Riemann ζ(3) and ζ(2).

We have analyzed the photochemical reaction for the deposition of SiO2 thin films at room temperature in photo-CVD using a vacuum ultraviolet (VUV) excimer lamp with reflection-absorption spectroscopy using a Fourier transform infrared spectrometer (RAS-FTIR). Tetraethoxyorthosilicate (TEOS) was used as a precursor and two types of excimer lamps were used as light sources. The reaction in VUV-CVD is divided into two stages: the reaction in the vapor phase, and the reaction on the surface of the substrate. In this work, we analyzed the latter stage. As a result of analyzing the spectra obtained, it was found that the main reaction for the formation of the SiO2 film was in the latter stage, in which the dissociation of Si–O bonds in Si–O–CH2 in the adsorbed fragments was preceded by the photo-dissociation of C2H5.

Photocatalytic hydrogen production was first detected in a high vacuum condition for platinum-loaded nanocrystalline anatase-titanium dioxide (TiO 2 ) thin films, using a newly developed monitoring system with a quadrupole mass spectrometer. In the presence of methanol of 10 À6 Torr, partial pressures of hydrogen (H 2 ) and formaldehyde (HCHO), generated due to the decomposition of methanol, were observed clearly to change simultaneously with the UV irradiation onto the TiO 2 films. Photolysis of gas-phase water was also detected, thus revealing that this new method is capable to evaluate sensitively such the photocatalytic activities in high vacuum at a real-time scale.

Characterization of n+-GaN/p−-SiC and n+-GaN/p+-SiC heterojunctions as well as fabrication of GaN/SiC heterojunction bipolar transistors (HBTs) using these heterojunctions is presented. The electroluminescence spectrum from n+-GaN/p+-SiC heterojunction diodes under forward bias clearly indicates electron injection from n+-GaN into p+-SiC. HBTs consisting of n+-GaN emitter /p+-SiC base/n−-SiC collector/n+-SiC substrate have been fabricated. Although clear common-base properties were obtained, the current gain was very low (10-4). SiC homojunction bipolar junction transistors (BJT) using the same base-collector junction exhibited a current gain value of 0.5, suggesting the low current gain of GaN/SiC HBTs originates from low emitter efficiency.

Photocatalytic hydrogen production with gas-phase reactions in high vacuum was examined for nanocrystalline anatase-type titanium dioxide (TiO2) thin films. The hydrogen generation process on platinized TiO2 specimens was investigated using a quadrupole mass spectrometer at a real-time scale under various partial pressures of gaseous methanol and water. As a result, hydrogen generation was successfully detected under ultraviolet ray (UV) illumination even in high vacuum (∼ 10−7 Torr). And the amount of produced H2 largely depends on the temperature of TiO2 samples, probably due to different surface states of TiO2. This study suggests the possibility of new high-speed H2 production system with gas-phase photocatalytic reactions.