EXCITONS IN SILICON NANOSTRUCTURES

The electronic structure of sigma-bonded silicon chains is calculated in the tight-binding approximation. The exciton spectrum is calculated by diagonalization of the full matrix of the Coulomb interaction taki ng into account the electron-hole exchange interaction. The energy, th e size and the radiative lifetime of excitons are computed as a functi on of the size of the chain. The results show that chains of silicon a toms are probably not at the origin of the visible luminescence of por ous silicon but could explain its fast band in the blue.