Direct band gap silicon quantum dots achieved via electronegative capping

Article

关键词: OPTICAL-PROPERTIES;    ELECTRONIC-PROPERTIES;    POROUS SILICON;    NANOCRYSTALS;    NANOPARTICLES;    CYTOTOXICITY;    NANOCLUSTERS;    LUMINESCENCE;    EMISSION;    CHLORINE;   

DOI  :  10.1103/PhysRevB.90.245439

来源: SCIE

【 摘 要 】

We propose a theoretical concept of switching between direct and indirect band gap character in silicon quantum dots (SiQDs) by the use of surface potential induced by the ligands or environment in which SiQDs are immersed-both cases are studied. Theoretical simulations show that the density of states of confined electrons in both real and k space can be dramatically altered by engineering the local electrostatic field. Especially interesting is modification of the lowest excited states, which appear in the Gamma valley for electronegative field that pulls electrons towards the SiQD surface. Opposite sign of the field does not have such effect at all. Hence we conclude a general trend of promotion of directlike radiative transitions by electronegative capping/environment. The rates are enhanced by more than two orders of magnitude compared to normal SiQDs, which can be as high as the values characteristic for direct band gap semiconductors. This model is in agreement with observed experimental properties of SiQDs with covalently bonded electronegative ligands.

【 授权许可】

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