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In this paper, we explore the properties of dynamical diffraction coefficients in orbital angular momentum resolved electron energy-loss magnetic chiral dichroism spectra, in a scanning transmission electron microscopy setup. We demonstrate that for basic zone axis geometries with fourfold or threefold symmetry the coefficients are constrained to have simplified forms. By exploiting these properties, we show how a dichroism spectrum accessible using this technique is only weakly dependent on sample thickness and, more generally, on dynamical diffraction effects. Our results indicate that in such cases it is possible to determine the orbital and spin components of atomic magnetic moments approximately from experimental spectra without the need for additional dynamical diffraction calculations.

In this paper the influence of 2s Bloch wave states on high angle annular dark field image contrast is studied quantitatively by Bloch wave and multislice simulations. We show that 2s states are excited beyond a critical Z value and cause a long period oscillation of the electron probe wave function that significantly influences the Z contrast. As a result, we find that the Z contrast for high Z alloys remains thickness dependent up to high sample thicknesses and this effect has to be considered for compositional analysis. In the special case of ordered alloys, the impact of 2s excitations on intensity provides a way to quantify long-range order phenomena in alloys with known composition.

Photoluminescence (PL), micro-PL, and PL excitation (PLE) spectroscopy for different light polarizations have been used to investigate the electronic properties of GaAs characterized by a dominant wurtzite (WZ) phase that forms in bare GaAs and in InGaAs/GaAs heterostructure (HS) nanowires (NWs). In both cases, the GaAs luminescence exhibits very narrow emission lines, which persist up to room temperature. At 10 K, the energy of the exciton ground state recombination of GaAs NWs is equal to 1.522–1.524 eV. In HS NWs, micro-PL combined with transmission electron microscopy pinpoints the tip of the GaAs section, with a dominant WZ phase, as the origin of that emission. In PLE, two very narrow excitonic absorptions at 1.523 and 1.631 eV involve different critical points of the WZ valence band (� 9v and � 7vu). The low-energy peak shows a negligible Stokes shift with respect to PL. At 10 K, a further weak and broad PLE signal is found at 1.59 eV. The possible attribution of these lines within the present knowledge of the WZ band structure is critically discussed.

Here a general approach to measure quantitatively with atomic resolution the distribution of a chemical species in a host matrix is derived and applied to a case study consisting of a layer of Si buried in a GaAs matrix. Simulations and experiments performed on $\mathrm{Si}∕\mathrm{GaAs}$ superlattices demonstrate a quasilinear dependence of the high-angle annular dark-field image intensity on the concentration of Si in the GaAs matrix. The results have been compared with those obtained by cross-sectional scanning tunneling microscopy on the same specimens.

Self-assembled $\mathrm{InAs}$ quantum dots (QDs) in $\mathrm{GaAs}$ layers were studied with a cathodoluminescense (CL) detection system combined with a transmission electron microscope. Three distinct peaks were observed to appear in the CL spectrum collected from a $1\ensuremath{\mu}{\mathrm{m}}^{2}$ region. The excitation power dependence of the CL spectra and monochromatic CL image observations identified those peaks that are the emissions associated with the ground state and excited state of the QDs in different size groups. Anomalous temperature dependence of those QD emission peaks was observed in the temperature range from 20 to around $100\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, where the emission intensities increase with temperature. Steady-state rate equations for the recombination processes of holes and excitons are proposed with introduction of a potential barrier at the interface between the $\mathrm{GaAs}$ layer and the wetting layer (WL). This model can explain the temperature dependence of the emission intensities from the QDs and WL in a wide temperature range.