EXCITED-STATES AND SIZE-DEPENDENT ELECTROOPTICAL PROPERTIES OF CDSXSE1-X QUANTUM DOTS

The electric-field response of CdS0.44Sc0.56 quantum dots in glass is studied as a function of particle size using electroabsorption spectro scopy. Up to six quantum-size levels can be observed in the data. The evolution of the transitions through many particle size provides evide nce for mixing of the valence bands due to quantum confinement. The el ectromodulated absorption data were fit with a first-derivative line-s hape function to separate the effects of the electric field on the ene rgy level, width, and oscillator strength associated with each electro n-hole state. For the lowest excited state in particles with radius R less than the bulk exciton Bohr radius, the size dependence of the fie ld-induced redshift is proportional to R(4) and the decrease in oscill ator strength is proportional to P-6, consistent with perturbation the ory. Although perturbation theory predicts the proper power-law depend ence, the magnitude of the response is many times smaller than predict ed. The redshift of the second excited state is found to increase as a a function of decreasing particle size with a maximum occurring for p articles with radius nearly equal to bulk Bohr excition radius.