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A radio frequency inductively coupled plasma (rf-ICP) nitrogen discharge was investigated to improve group III nitride growth on Si substrates. Two modes of the rf-ICP discharge, low brightness (LB) and high brightness (HB) discharges, were successfully controlled through mode transition. Direct irradiation and indirect irradiation of nitrogen atoms were applied for the growth of group III nitrides. As an application of indirect irradiation of nitrogen atoms, the growth of $\beta$-Si3N4using interface reaction epitaxy (IRE) was studied. As applications of direct irradiation of nitrogen atoms, activity modulation migration-enhanced epitaxy (AM-MEE) and plasma-assisted molecular beam epitaxy (PA-MBE), which are atomic layer epitaxy (ALE) methods, are demonstrated. These growth systems operate to realize a single-growth process from a Si substrate to an AlN or GaN epitaxial layer, i.e., through preparation of a double buffer (DBL) layer of AlN/$\beta$-Si3N4/Si after the growth of IRE $\beta$-Si3N4and IRE AlN. The electron emission due to the self-ionization of nitrogen atoms on a negatively biased electrode is demonstrated to measure in situdirect and indirect nitrogen atom fluxes during the growth.

The microwave ionic conductivity σ of single-crystals of K-Mg priderite ( a hollandite type compound ) K1·6Mg0·8Ti7·2O16has been measured using a standing wave method at 9.54 and 32.8 GHz from 83 to 616 K. The results of σT−1Tcharacteristic are divided into two regions, one is the part of higher temperatures I and the other is the part of lower temperatures II. As the ionic conductivity at 32.8 GHz at the region I is interpreted by the configurational model proposed by Bayeler et al., the frequency-independent intrinsic ionic conductivity dominated by the configurational model is predicted to be observed at higher frequencies than 32.8 GHz.

The title materials, mutually isostructural, have an intergrowth structure of rutile and β-gallia, and the structure contains one-dimensional large channels occupied by alkali ions. The free diameter of these channels is about 3.4 Å at minimum, which is significantly larger than the effective ionic radii of K+and Rb+. Their lattice constants hardly change in spite of a large size difference among K+, Rb+, and Cs+. The electron density distributions show a distinct delocalization of the alkali ions on the channel axis, which is attributed to the large number of energetically quasi-equivalent sites available for the mobile ions due to the disappearance of virtual bottlenecks in the tunnels. Diffuse scatterings, which imply some short-range ordering among the alkali ions, were revealed by X-ray and electron diffraction techniques. They are very weak, but suggest that the ordering is similar to that in K2vMgxTi8−xO16.

The motion of K+ion in the one-dimensional ionic conductor, Al-priderite, with hollandite-type structure was investigated using 27Al in the framework as a probe. The temperature dependence of the spin-lattice relaxation time T1showed that it is divided into two regions. In the low temperature region where the motion is dominated by the intrinsic barrier, the frequency dependence of T1is proportional to ω1.5. The slope, δln(T1)/δ(1/T), in the low temperature side gives a small value of 29 meV. In the high temperature region, where T1is influenced by the long range fluctuation of K+ion over the impurity barriers, T1becomes independent of the frequency, and this behavior may be due to the existence of reflecting walls introduced by impurities with high barrier height which K+ion can not pass over.

The frequency- and temperature-dependences of a.c. ionic conductivity of one-dimensional superionic conductors K-priderites, K1.6Mg0.8Ti7.2O16(KMTO) and K1.6Al1.6Ti6.4O16(KATO), which were grown by using a flux with high grade purity, were investigated from 100 Hz to 10 MHz. The complex ionic conductivity along a c-axis was analyzed by using an equivalent circuit constructed by considering the frequency-dependent ionic conductivity σmband the frequency-independent ionic conductivity σdcwhich was not observed for samples grown by using a flux with normal grade purity. The σdcwas thermally activated and the activation energies for KMTO and KATO were 0.26 and 0.30 eV respectively. The lateral conductivity was very small.