Yu. I. Mazur at al. APL 98 , 083118 (2011) Yu. I. Mazur at al. Nanoresearch (submited)

1. Materials World Network: Understanding & controlling optical excitations in individual hybrid nanostructuresGregory J. Salamo, University of Arkansas, DMR 1008107 The process of carrier or energy exchange in coupled nanoscopic and mesoscopic systems is one of the most fundamental topics in science, crossing every discipline from biology and chemistry to materials science. We have designed a test system based on semiconductor quantum dots (QD) placed in close proximity to a quantum well (QW). By controllably varying the energy level spectrum of the QW we adjust the specific coupling conditions between the two-dimensional (2D) QW and the zero-dimensional (0D) QDs. This creates an opportunity to controllably hybridize the electronic states between these two systems with different dimensionality. The results of this study suggest that the hybridization of radiating quantum-confined system (0D, QDs) with another quantum-confined system (2D, QW) which can be controlled based on excitation conditions to not radiate within the lifetime of the QDs will largely enhance the QD emission. Here, the QW acts as a basin of charge carriers, injecting them without loss directly into the 0D emitters. Use of this result could immediately impact solid state lighting and photonic devices in producing a more efficient light source. However, the greater impact of the general understanding of coupling and charge transfer in confined systems will influence research on charge transfer dynamics in complex chemical and biological systems. Yu Photoluminescence spectra taken at 10K of the hybrid quantum dot (QD) – quantum well (QW) system shown at top in the transmission electron microscope image and diagram. Sharp increase in signal for higher alloy concentrations (x) demonstrates a controlled turn-on of quantum mechanical tunneling of charges between the dot and well as the filled states line up across the barrier as shown in the diagram at the bottom. Yu. I. Mazur at al. APL98, 083118 (2011) Yu. I. Mazur at al. Nanoresearch (submited)

2. Materials World Network: Understanding & controlling optical excitations in individual hybrid nanostructures Gregory J. Salamo, University of Arkansas, DMR 1008107 This international research program promotes student education by providing support for both undergraduate and graduate students at the University of Arkansas to conduct research in ultrafast and nano-optical spectroscopy in Germany, and undergraduate and graduate students at the University of Oldenburg to learn to grow and characterize their own samples in Arkansas. The students experience the different research and social cultures of another country while making significant progress on their research through the training provided by the unique facilities and skills of their international research partner. UA student Chris Thomason, used near field spectroscopy available and well understood at UO to initiate his thesis work on quantum dot pairs which were grown at UA. At the same time UO graduate student Robert Bergansky learned how to use electron beam lithography facilities at UA to process samples with the goal of creating nanometer scale metal gratings to investigate plasmon-exciton coupling with GaAs/AlGaAs quantum wells. Ph.D. student Chris Thomason from the University of Arkansas currently studying near field spectroscopy at the University of Oldenburg