OPTICAL-ABSORPTION AND PHOTOLUMINESCENCE OF SELF-ASSEMBLED SILICON QUANTUM DOTS

Hemispherical silicon quantum dots with an average height of 6.3, 3.3 or 1-2 nm covered with an ultrathin SiO2 layer have been spontaneously formed on SiO2/Si(100) and quartz substrates by the thermal decomposi tion of pure silane at low pressure. It is found that the optical abso rption edge determined from photothermal deflection spectroscopy exhib its blue shifts from 1.9 to 2.5 eV when the average dot size was decre ased from 6.3 to 1-2 nm and correspondingly, the luminescence peak ene rgy increases from 1.2 to 1.4 eV at room temperature. The large Stokes shift suggests that the localized, radiative recombination centers ex isting presumably in the SiO2/Si dot interface are responsible for the efficient; room-temperature luminescence from the silicon quantum dot s.