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The muon spin relaxation in the Al-Mg dilute alloy was measured under the zero external field from 34 to 120 K, and the observed spectra were fitted to the calculated spin relaxation function of the two state model which is taking account of both trapping and detrapping mechanisms. Thus, the muon behavior in Al in the presence of impurity traps were able to be visualized: a muon diffuses in the incoherent hopping process with one phonon assistance, while it is then captured by a trap in a diffusion control process, and detrapped in the thermal activation process.

Electronic states and depolarization phenomena are studied for theμ+ in cis- and transpolyacetylene (CH)x. Formation of weakly bound muonium-like paramagnetic state is found in cis-(CH)x at room temperature, while diamagneticμ+ state is formed in trans-(CH)x. The origin of this clear difference might reflect properties of excitation modes in these two-isomers.

The reaction rate of the reaction of Mu and NO2 was measured by means of transverse field MuSR in Ar gas containing NO2. A pulsed surface muon beam was employed for the experiment. The rate constant of the reaction was found to be substantially larger than that of the analogous H reaction.

Abstract: Surface muons produced in UT-MSL were introduced into argon gas of 4.00.2 atm with NO2 (0–30 ppm), and muonium signals were detected in the presence of a transverse (1.7–3.4 G) and a longitudinal magnetic field (0–3.5 kG) at 2951 K. The cross section for the transverse relaxation was (11.01.0)10−16 cm2. The relaxation rates in different longitudinal magnetic fields show that the rate does not follow the conventional equation which assumes that the relaxation occurs mainly by spin-exchange interaction. Similar measurements were performed for the Mu+O2 system. These findings indicate that chemical reactions contribute to these relaxation rates.

The enhancement mode AlGaN/GaN hybrid MOS-HFETs on Si substrates have been demonstrated. The breakdown voltage of over 1.71 kV was achieved by investigating the epitaxial structure. Furthermore, a high integrity SiO2/Al2O3gate stack has been demonstrated for GaN MOSFETs. The SiO2film formed on GaN by the MW-PECVD exhibits good properties compared that by the LP-CVD. Then, by incorporating the advantages of both of SiO2with a high insulating characteristics and Al2O3with good interface characteristics, the SiO2/Al2O3gate stack structure has been employed in GaN MOS devices. It is shown that a low interface state density between gate insulator and GaN, a high breakdown field, and a large charge-to-breakdown by applying 3-nm Al2O3in this structure. The SiO2/Al2O3gate stack has also been applied to AlGaN/GaN hybrid MOS-HFET and excellent properties with the threshold voltage of 4.2 V and the maximum field-effect mobility of 192 cm2/Vs are shown in the transistor.