No abstract

No abstract

We prepared resistive switching Al-AlO x multilayered junctions and observed considerably improved endurance properties. The mechanism of the observed resistance switching basically reflects the filament model. The temperature dependence of the transport in each resistance state revealed additional features, that is a well-defined thermal activation behavior in the high-resistance state is not observed in the layered device and the metallic conduction in the low-resistance state is not affected. The improved endurance properties are discussed in terms of the increased effective number of active regions, where the Reset and Set processes probably occur before a permanent dielectric breakdown.

We investigated deep-level traps formed in Al0.2Ga0.8N/GaN heterostructures grown using plasma-assisted molecular beam epitaxy and by performing deep level transient spectroscopy (DLTS). Two electron traps with activation energies of Ec−150 meV and Ec−250 meV were observed, and their capture cross-sections (σT) were estimated to be 2.0×10−18 cm2 and 1.1×10−17 cm2, respectively. Different behaviors in the dependence of DLTS on filling pulse length confirm that the traps originated from N vacancies and dislocations. The amplitude of the dislocation-induced DLTS signal was reduced significantly by high-temperature rapid thermal annealing under N2 ambient after hydrogen treatment due to the reduction in dislocation density.

Three low-lying vibrational states of molecular systems are responsible for the signals of linear and third-order nonlinear vibrational spectroscopies. Theoretical studies based on mixed quantum/classical calculations provide a powerful way to analyze those experiments. A statistically meaningful result can be obtained from the calculations by solving the vibrational Schrödinger equation over many numbers of molecular configurations. The discrete variable representation (DVR) method is a useful technique to calculate vibrational eigenstates subject to an arbitrary anharmonic potential surface. Considering the large number of molecular configurations over which the DVR calculations are repeated, the calculations are desired to be optimized in balance between the cost and accuracy. We determine a dimension of the DVR method which appears to be optimum for the calculations of the three states of molecular vibrations with anharmonic strengths often found in realistic molecular systems. We apply the numerical technique to calculate the local OH stretching frequencies of liquid water, which are well known to be widely distributed due to the inhomogeneity in molecular configuration, and found that the frequencies of the 0-1 and 1-2 transitions are highly correlated. An empirical relation between the two frequencies is suggested and compared with the experimental data of nonlinear IR spectroscopies.