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We used a low temperature near-field scanning optical microscopy (NSOM) to study a formation of Wigner molecules (WMs) in the emission spectra of self-organized InP/GaInP QDs having up to seven electrons. We used a Schottky diode structure for the electrostatic control of the number of the electrons (N) in QD, and we observed the emission of the charged excitons (for N < 3) and of the WMs (for N > 2) in the regime of weak Wigner localization. We show, that a contribution of whispering gallery modes (WGMs) of the electrons and rearrangement of the electrons between the WM and WGM states in the QDs, can explain the anomalous dependence of NSOM image size on the quantum confinement observed for some dots. [ABSTRACT FROM AUTHOR]

The emissivity of unstrained quantum-dimensional InP/AlInAs nanostructures and their lasing properties in microdisk cavities prepared by wet etching have been studied. For as-prepared structures, it has been found that they radiate owing to quantum-dimensional InP islands 50-300 nm in diameter. At temperatures below 160 K, whispering gallery modes have been observed in the microdisks. Experimental data on the PL intensity for microcavity modes versus the pump power, which were obtained at liquid helium temperature, have made it possible to find the lasing threshold, 50 W/cm. The half-width of the laser line at above-threshold powers equals 0.06 nm, which corresponds to a Q factor of 15 000. [ABSTRACT FROM AUTHOR]

A mechanically induced solid-state reaction method for the synthesis of organic-inorganic hybrid perovskites, such as methylammonium lead iodide (CHNHPbI) is reported. The perovskites were synthesized both in bulk and AlO-supported forms. The phase- and structural-formation mechanisms of such perovskites are also investigated. The experiments suggest that diffusion of PbI into CHNHI crystals is a rate-limiting step of the reaction process. It is also shown that water (humidity) significantly influences the reaction kinetics. UV-Vis-NIR absorption and photoluminescence spectroscopies indicate that the band edge and emission characteristics of the as-fabricated materials strongly depend on their particle size. [ABSTRACT FROM AUTHOR]