Electron density of an artificial atom. Specifically, the image shown displays the excited electron state in an Indium Arsenide (InAs) / Gallium Arsenide (GaAs) self-assembled quantum dot. The nanometer-scaled structure of the semiconductor InAs embedded in GaAs can confine electrons much like a proton can attract an electron in a hydrogen atom. This artificial atom is 100 times larger than a natural atom, and its properties can be manipulated by material composition, size and shape.
The semiconductor InAs can be grown as a crystal on top of a GaAs substrate. Since the natural InAs lattice constant is larger than that of GaAs, the material can clump up to form perfect crystal structures at nanoscale, that can take on pyramidal or dome shapes. The typical sizes of these quantum dots are 20nm in diameter and 5nm in height. The InAs material is typically capped and overgrown with GaAs. The central structure can confine additional electrons and form an artificial atom. These artificial atoms have the ability to absorb and emit light similar to natural atoms. The frequency or wavelength of this optical activity can be designed by quantum dot size, shape and material composition. The image shows an excited electron state in such InAs quantum dot. The electron density is colored by the orbital-resolved s, p, d character of the electron wavefunction contribution.
The wavefunction was computed with the Nanoelectronic Modeling Tool (NEMO 3D) and visualized with the nanoVIZ tool on nanoHUB.org.
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