Stark effect and single-electron charging in silicon nanocrystal quantum dots

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Abstract
In this article, we investigate numerically the electronic structure of semispherical nanocrystals in quantum-dot based flash memory devices. We model three different sizes of nanocrystals with diameters of 125, 70, and 50 Å by solving self-consistently a system of three-dimensional (3D) Kohn–Sham and Poisson equations. We show that the unique combination of symmetries in the bandstructure and the 3D confinement geometry produce Stark effects with energy-level crossings in the nanocrystals. We also show that the quantum states in large nanocrystals (125 Å diameter) respond markedly different to the applied control-gate electric field compared to the smaller nanocrystals (diameter <70 Å). Finally, we simulate single-electron charging and obtain the addition energy spectrum of the 125-Å-diam nanocrystal.