Electrodeposition of CdS quantum dots and their optoelectronic characterization by photoelectrochemical and scanning probe spectroscopies

CdS quantum dots (QDs) have been electrodeposited onto textured gold substr ates from a nonaqueous electrolyte containing Cd(ClO4)(2) and elemental S. The initial deposit consisted of very small (about 3 nm) nanocrystals of Cd S which were partially oriented with the Au substrate. With increasing depo sit thickness, the crystal size increased and the degree of orientation dec reased. Photocurrent spectroscopy and I-V spectroscopy, using a conducting scanning force microscope tip, were used to measure the CdS bandgap variati ons due to size quantization. The latter method also revealed room temperat ure conductivity peaks assigned to Coulomb charging of the QDs and evidence for charge tunneling into higher discrete energy levels. (C) 1999 Academic Press.