Aug 31, 2016
When stressed, quantum dots respond in unison !
Contact : Julien CLAUDON

Scanning electron micrograph obtained for the core-shell structures under study.

It has been shown in recent years that mechanical stress can be used to tune the electronic and optical properties of semiconductor quantum dots. For instance, this approach has been implemented to adjust finely the emission wavelength of quantum dot single photon sources. In view of real applications, it is highly desirable to have all dots responding the same way to a given applied stress. Our team has introduced a novel approach which enables to apply a rigorously identical stress to a collection of quantum dots, so as to test their response homogeneity. Staring from an epitaxial sample containing a plane of quantum dots, we first define 300 nm diameter cylinders by reactive ionic etching, containing few (3 to 10) dots. We deposit next a thin conformal amorphous layer of silica by CVD at high temperature. Because of the difference of the thermal expansion coefficients between the two materials, the silica shell exerts  stress on the GaAs core, as well as on the quantum dots it contains. A modelling of the strain tensor at 4K (temperature at which we perform our experiment) shows that the core material experiences a highly uniform strain, and that it is mainly expanded along the cylinder axis. We observe by photoluminescence a very similar emission wavelength shift for all quantum dots, which highlights a very good homogeneity  of their response to applied stress. These results open interesting prospects in the fields of nanophotonics and quantum sensing.   

 

Maps of the strain field components, as calculated for these structures within the plane containing the quantum dots.

Référence:  

Large and Uniform Optical Emission Shifts in Quantum Dots Strained along Their Growth Axis,

Petr Stepanov, Marta Elzo-Aizarna, Joël Bleuse, Nitin S. Malik, Yoann Curé, Eric Gautier, Vincent Favre-Nicolin, Jean-Michel Gérard and Julien Claudon,

Nano Letters 16, 3215 (2016)

http://dx.doi.org/10.1021/acs.nanolett.6b00678 

 

Last update : 09/01 2016 (1184)

 

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