QUANTUM SIZE EFFECTS AND ENHANCEMENT OF THE OSCILLATOR STRENGTH OF EXCITONS IN CHAINS OF SILICON ATOMS

We have studied the size-dependent optical properties of confined excitons in chainlike Si-backbone polymers with 5-110 Si atoms. The blueshift of the lowest exciton state was observed with decreasing number of Si atoms. In chains having 20 Si atoms or less, the oscillator strength per Si atom for the lowest exciton linearly increases with increasing number of Si atoms. The radiative-decay rate of excitons is in proportion to the square of the number of Si atoms. These results are experimental evidence of the quantum size effect of excitons in chains of Si atoms.