Effect of growth interruption time on the quality of InAs/GaSb type-II superlattice grown by molecular beam epitaxy

We systematically investigate the influence of growth interruption time on the properties of InAs/GaSb type-II superlattices (T2SLs) epitaxial materials grown by molecular beam epitaxy (MBE). X-ray diffraction (XRD) and atomic force microscope (AFM) are used to characterize the material quality and morphology. The full width at half maximum (FWHM) of the XRD 0th satellite peaks ranges from 32'' to 41'', and the root mean square (RMS) roughness on a 5 μm×5 μm scan area is 0.2 nm. Photoluminescence (PL) test is used to reveal the influence of the growth interruption time on the optical property. Grazing incidence X-ray reflectivity (GIXRR) measurements are performed to analyze the roughness of the interface. The interface roughness (0.24 nm) is optimal when the interruption time is 0.5 s. The crystal quality of T2SLs can be optimized with appropriate interruption time by MBE, which is a guide for the material epitaxy of high performance T2SL infrared detector.     

Chaotic electronic scattering with He(+)

We investigate classical electronic collisions with a He(+) ion. Scattering functions, such as the scattering angle, collisional time, or energy of the outgoing electron, all exhibit an interesting hierarchial self-similar structure, which can be interpreted in terms of the indefinite number of electronic returns to the vicinity of the nucleus, encounters between electrons, and Keplerian excursions of electrons during the collisional processes. Based on this mechanism a binary coding is introduced to organize the dynamics of this three-body system and to provide an understanding of the self-similarity among generations of scale magnification, which yields escape rates that vary with the sectional cut into the parameter space. The self-similarity displayed within a single generation, on the other hand, can be simply tied to the periods of the two independent electronic excursions. The physical interpretation and the symbolic dynamics introduced here are generally useful for three-body collisional systems, including atomic, molecular, or stellar collisions.