The background virtual image represents a gallium arsenide (GaAs) semiconductor crystal embedding an indium arsenide (InAs) quantum dot buried 7 nm beneath the surface.
The 1018 atoms are distributed on the sites of a Zinc-Blend structure exhibiting 4*3m symmetry. The quantum dot is lens shaped, approximatively 3 nm in height and 25 nm in diameter. The quantum dot relies on a thin bidimensionnal layer, called the wetting layer, which formation is related to the growth process and is approximatively two InAs monolayers thick.
Strictly speaking the structure is not a crystal since it is not periodic, because the indium atoms forming the quantum dot break down the translational symmetry of the GaAs matrix, and the matrix is actually strained by the presence of the bigger indium atoms. However, because most of the basic properties of such a quantum dot can be investigated considering a piecewise-crystalline structure: crystalline in the InAs volume and crystalline in the GaAs barriers, this structure is still referred to as a crystal. The quantum dot is more like a perturbation (though a strong one) to the lattice periodicity as is a dopant or impurity in a semiconductor. This piecewise-crystalline point of view has lead to one of the most prolific theories and modelings of heterostructures based on the envelope function theory. The home page displays the envelope function of an electron confined in a quantum dot and calculated using such a three dimensional 8 band k.p envelope function theory which is part of the workshop scope.
The background image is generated using CrystalLens, a specific C++ program developed since 2003 by one of the organizers (Sébastien Sauvage) interfaced with presently available renderers in common modelers. The fast generation of such an image containing multitrillions atoms and equivalent thousand frame long animations is not as straightforward as it seems.
