Light from Si-nanoparticle systems - A comprehensive view

Si in the form of finely divided crystalline particles with nanometer dimensions shows an efficient visible luminescence at room temperature. We examine the experimental facts for differently prepared nanoparticle systems, such as electrochemically etched porous Si, layers and particles synthesized from the gas phase and particles precipitated in a glassy SiO2-matrix after Si+-implantation. The observations preclude a simple interpretation of the light emission in terms of the physics of quantum dots. They also show it as unlikely that a single, specific molecular agent can account for the light. We provide a comprehensive view of the emission mechanism in which the luminescing Si is an interactive composite system with a crystalline core and a passivant mantle layer of perturbed Si bonded to O and H. The predominant emission is via the electronic states of the perturbed Si. We note many similarities with the characteristics of luminescing a-Si:H.