Field-induced Stark effects in Ag-coated CdS quantum dots

Field-induced Stark effects in Ag-coated CdS quantum dot structures are presented. We observe clear exciton peaks due to the quantum confinement effect and the surface plasmon effect in Ag-coated CdS quantum dot fabricated by gamma ray irradiation method. In addition, we observed also a dominant red-shift of the CdS exciton absorption peak as the Wannier Stark effect, implying the strong local field effect in the metal-coated semiconductor composite quantum dot system. The Stark shift of the exciton peak is investigated as a function of the local field for different silver thickness and various sizes of quantum dots based on the effective-mass Hamiltonian using the numerical-matrix-diagonalization method.