Mathematics for various disciplines Atomistic view of InAs quantum dot self-assembly from inside the growth chamber

2006-11-29 10:30 - 2006-11-29 11:30
Graduate School of Mathematical Sciences the University of Tokyo, Room #056
Shiro Tsukamoto (Tokyo University)
A 'quantum dot' is a tiny region of a solid, typically just nanometres in each direction, in which electrons can be confined. Semiconductor quantum dots are the focus of intense research geared towards exploiting this property for electronic devices. The most economical method of producing quantum dots is by self-assembly, where billions of dots can be grown simultaneously. The precise mechanism of self-assembly is not understood and is hampering efforts to control the characteristics of the dots. We have used a unique microscope to directly image semiconductor quantumdots as they are growing, which is a unique scanningtunnelling microscope placed within the molecular beamepitaxy growth chamber. The images elucidate the mechanismof InAs quantum dot nucleation on GaAs(001) substrate,demonstrating directly that not all deposited In isinitially incorporated into the lattice, hence providing alarge supply of material to rapidly form quantum dots viaislands containing tens of atoms. kinetic Monte Carlosimulations based on first-principles calculations showthat alloy fluctuations in the InGaAs wetting layer priorto are crucial in determining nucleation sites.