By taking a two-dimensional solid local resonant phononic crystal as an example, we investigated the mechanism of the defect state on a subwavelength scale. It is well known that, when the working wavelength is much greater than the distance between resonators, the dispersion of the phononic crystal is insensitive to the lattice structure, and the whole structure can be described in terms of the effective medium theory. As a result, it is hard to introduce a defect state in the system by a local real-space disorder. It is shown in this paper that the dispersion of the local resonant phononic crystal can be understood from the long-range feature of the interaction between resonators, so the creation of a defect state in the system is in fact to break such a long-range interaction. Based on this understanding, the mechanisms of the recently reported methods, that are used to create defect states, are discussed. In addition, a waveguide structure that can guide the longitude or transverse waves separately is realized by introducing an anisotropic defect resonator.
ZnO/Zn0.9Mg0.1O/ZnO heterostructure was grown by radio frequency plasma-assisted molecular beam epitaxy on a sapphire (0001) substrate. By using RBS/C, the depth-dependent elastic strain was deduced. The strain changes from negative to positive from interface to surface, and the value is higher at the depth close to the interface (also at the interface between ZnO and Zn0.9Mg0.1O) and decreases towards the surface. The negative tetragonal distortion was explained by considering the lattice mismatch and thermal mismatch between ZnO and sapphire substrate, and the positive distortion is due to the tensile strain in the parallel direction of Zn0.9Mg0.1O and the gradual release of the strain.
The GaN films grown on sapphire by metal-organic chemical vapor deposition (MOCVD) have excellent crystalline quality (χmin=2.00%). Combining Rutherford backscattering/channeling (RBS/C) and high-resolution X-ray diffraction (HXRD) measurements, we investigate the radiation damage in GaN films with various doses and angles of Mg+-implantation. The results of experiments reveal that the radiation damage rises with the increasing implantation dose. Under the dose of 1×1015atom/cm2, χmin is less than 4.78%, and when implantation dose exceeds the threshold of 1×1016atom/cm2, χmin will be up to 29.5%. Random implantation causes more serious damage than channeled implantation, and in a definite range the damage level rises with a larger implantation angle. At the implantation angles of 0°,4°,6°and 9°deviating from〈0001〉, χmin(%)is 6.28,8.46,10.06 and 10.85, respectively, at a dose of 4×1015atom/cm2. After annealing at 700℃ for 10min and then 1050℃ for 20s, the damage recovers to some extend. The crystalline quality of the sample with 1×1016atom/cm2 implanted was reduced to 19.08%. In addition, the annealing condition of 1000℃ for 30s is more efficient and the damage recovers better.
The thermal stability is improved in a magnetic tunnel junction with a nano-oxide layer induced between the antiferromagnetic and pinned ferromagnetic layers, in which the annealing temperature is increased about 40℃. By using Rutherford backscattering spectroscopy, it has been found that the interdiffusion of Mn atoms, responsible for the decrease of TMR during the annealing process, is uppressed across such nano-oxide layer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.