Impact of interface on the effective band gap of Si quantum dots (talk)

We investigated the ground state of approximants consisting of ≤165 Si atoms (dQD≤ 18.5 Å) with full termination of the Si interface with F-, OH-, NH2-, CH3-and H-groups simulating Si QDs embedded in a Fluoride, SiO2, Si3N4, SiC matrix and vacuum, respectively, with ab-initio methods. As the polarity of the Si/matrix interface increases the optical bandgap becomes increasingly dominated by charge transfer at the interface rather than by quantum confinement. For Si QDs with dQD = 7.3 to 37 Å, the interface determines the electronic structure in competition with quantum confinement for strong polar interfaces (NH2, OH) and for H- and CH3-terminations as a secondary effect. We present an estimate of band gaps of different QD materials with the same interface and interprete the ab-initio results in conventional quantum mechanics.