Materials World Network: Understanding & controllingoptical excitations in individual hybrid nanostructuresGregory J. Salamo, University of Arkansas, DMR 1008107
The process of carrier or energy exchange in couplednanoscopic and mesoscopic systems is one of the mostfundamental topics in science, crossing every disciplinefrom biology and chemistry to materials science.
We have designed a test system based on semiconductorquantum dots (QD) placed in close proximity to a quantumwell (QW). By controllably varying the energy levelspectrum of the QW we adjust the specific couplingconditions between the two-dimensional (2D) QW and thezero-dimensional (0D) QDs. This creates an opportunityto controllably hybridize the electronic states betweenthese two systems with different dimensionality.
The results of this study suggest that the hybridization ofradiating quantum-confined system (0D, QDs) withanother quantum-confined system (2D, QW) which can becontrolled based on excitation conditions to not radiatewithin the lifetime of the QDs will largely enhance the QDemission. Here, the QW acts as a basin of chargecarriers, injecting them without loss directly into the 0Demitters.
Use of this result could immediately impact solid statelighting and photonic devices in producing a more efficientlight source. However, the greater impact of the generalunderstanding of coupling and charge transfer in confinedsystems will influence research on charge transferdynamics 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 transmissionelectron microscope image and diagram. Sharp increase in signal forhigher alloy concentrations (x) demonstrates a controlled turn-on ofquantum mechanical tunneling of charges between the dot and well asthe filled states line up across the barrier as shown in the diagram at thebottom.
Yu. I. Mazur at al. APL 98, 083118 (2011)
Yu. I. Mazur at al. Nanoresearch (submited)
Materials World Network: Understanding & controllingoptical excitations in individual hybrid nanostructures Gregory J. Salamo, University of Arkansas, DMR 1008107
Ph.D. student Chris Thomason from the University ofArkansas currently studying near field spectroscopy atthe University of Oldenburg
This international research program promotesstudent education by providing support for bothundergraduate and graduate students at theUniversity of Arkansas to conduct research inultrafast and nano-optical spectroscopy in Germany,and undergraduate and graduate students at theUniversity of Oldenburg to learn to grow andcharacterize their own samples in Arkansas. Thestudents experience the different research and socialcultures of another country while making significantprogress on their research through the trainingprovided by the unique facilities and skills of theirinternational research partner.
UA student Chris Thomason, used near fieldspectroscopy available and well understood at UO toinitiate his thesis work on quantum dot pairs whichwere grown at UA. At the same time UO graduatestudent Robert Bergansky learned how to useelectron beam lithography facilities at UA to processsamples with the goal of creating nanometer scalemetal gratings to investigate plasmon-excitoncoupling with GaAs/AlGaAs quantum wells.