TRANSIENT PHOTOCURRENT SPECTROSCOPY - ELECTRICAL DETECTION OF OPTICAL-ABSORPTION FOR SUPPORTED SEMICONDUCTOR NANOCRYSTALS IN A SIMPLE DEVICE GEOMETRY

The optical absorption of supported cadmium sulfide nanocrystals is di rectly detected as an electrical signal using a method described in th is letter. Cadmium sulfide nanocrystals were epitaxially deposited ont o highly oriented, pyrolitic graphite surfaces using a hybrid electroc hemical/chemical synthesis method. The resulting submonolayer of cadmi um sulfide nanocrystals was then covered with a thin (10-100 nm) insul ating Formvar layer and a semitransparent gold top electrode. We expos ed this structure to monochromatic chopped light and detected the tran sient photocurrent phase-sensitively and without applied bias. In the resulting device spectra, the absorption edge of the cadmium sulfide n anocrystals was clearly discernible at room temperature. The device re sponse spectrum is compared with photoluminescence spectra acquired fo r the quantum dots in these devices at 20 K. (C) 1998 American Institu te of Physics.