A phononic crystal of aluminum rods with an asymmetric cross section in water is used for the study of Anderson localization of sound. Due to asymmetry, these scatterers may be arranged in three different configurations: a periodic 2D structure, a random structure with 2D disorder, and a random structure with 1D disorder. The last configuration where the rods are equally oriented within the columns and disoriented along the rows is fabricated for the experimental study of 1D Anderson localization in the 2D random system. An exponentially weakening transmission of the ultrasound is demonstrated for the waves propagating along the direction of disorder. In the perpendicular direction where the scatterers are ordered, sound propagates as an extended (delocalized) wave. The localization length is controlled by the degree of disorder. For weak disorder, when orientations of the rods weakly fluctuate around a given direction, Thouless’s theoretical prediction for the scaling of the Lyapunov exponent with disorder is experimentally observed for a mode within the transmission band. For the sound mode close to the band edge, anomalous scaling is confirmed.

In-situ measurements such as deep level transient spectroscopy (DLTS) provide reliable information for the identification of defects in electronic devices. For GaN-based devices exposed to swift heavy ion (SHI) irradiation, in situ DLTS investigations are not reported. The defect characterization of irradiated devices has significant relevance in the reliability testing of devices for space applications, detectors for high energy physics experiments, nuclear radiation environments near reactors and for device engineers to design better and high-performance electronic components. The present work reports on the identification of defects by employing in situ DLTS in Pt/n-GaN Schottky devices before and after SHI irradiation by 200 MeV 107 Ag 14+ ions at various fluences in the range of 1×10 10 to 1×10 11 ions cm −2 . For pristine or un-irradiated diodes, trap levels at 0.173, 0.504, 0.283 and 1.012 eV below the conduction edge are observed which are reported as growth-related defects in GaN. The ion beam introduces more electron and hole traps in the bandgap. A significant increase in interface state density was instigated by irradiation which practically pinned the Schottky barrier height at 0.73 eV at an experimental time scale. The origin of these defects was compared and discussed based on literature.

A detailed analysis of defect assisted transport properties of GaN after irradiation is carried out. Unintentionally doped GaN samples were irradiated by a 100 MeV oxygen ion beam and a 200 MeV silver ion beam at various fluences between 1 × 1010 ions/cm2 and 5 × 1011 ions/cm2. Thermopower and Hall effect measurements were done on pristine and irradiated GaN samples at variable temperatures. An increase in the thermopower with temperature as well as on irradiation (with respect to pristine GaN) was observed. Electrical conductivity and Hall mobility decreased on irradiation, suggesting scattering of charge carriers due to the formation of defects. A qualitative study of activation energy due to thermopower and conductivity is done by the scattering mechanism using different theoretical models to determine the transport path of the carriers. The observed increase in thermopower of GaN after irradiation suggests a probable hopping mechanism due to the presence of energy levels in the bandgap.

The periodic field dependence of magnetic anisotropy (de Haas-van Alphen effect) has been studied for bismuth and zinc crystals by the torque method between about 1.5 and 32 kG at 4.19°K and about 1.5° K; in each case the orientation was chosen so that only a single fundamental periodicity was present. Particular attention was paid to the phase and harmonic content of the oscillations and to the form of the field dependence of amplitude. For bismuth good agreement was found with the theoretical formula except that the signs of the fundamental and the odd harmonics had to be reversed. For zinc the field dependence of amplitude at high fields was quite at variance with the theoretical formula and (probably in consequence) the harmonics were much weaker than in bismuth; the phases of the fundamental and the first harmonic were quite different from those of the theoretical formula. A slight field dependence was found for bismuth even at 85° K, similar to the rather more marked one previously found in zinc. Oscillations of very much shorter period than the main ones were observed in zinc at the highest fields and their characteristics were briefly studied. Qualitative observations were made of the very short-period oscillations in a lead crystal, previously only observed by an impulsive method at much higher fields. No oscillations could be detected in copper, silver or gold crystals.

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