Current-voltage characteristics of single CdSe colloidal nanodots measured by conductive-tip atomic force microscopy

We have investigated current-voltage characteristics of individual CdSe colloidal nanodots by conductive-tip atomic force microscopy (AFM). The colloidal nanodots were spun-coat and scattered on a self-assembled monolayer of thiophene molecules formed on Au (111) surfaces for single dot measurements. A thin SiO2 layer was deposited on the sample surface in order to prevent the dots being moved by the tip during measurement. We imaged the topography of isolated single dots by AFM operated in contact mode, and measured current-voltage characteristics with the conductive tip positioned on single dots; large conductivity changes which suggest resonant tunneling through,a quantized energy level in the dot was observed even at room temperature.