Design and fabrication of a photosensing nanodevice structure with CdSe and Au nanoparticles on a silicon chip

A newly developed four-layered photosensing nanodevice was fabricated by integrating nanoparticles (NPs) on a silicon substrate. Through ionic interaction, negatively charged Au NPs (∼15 nm) were assembled in alternate layers with positively charged CdSe NPs (∼5 nm) on the silicon oxide surface between the two Al electrodes. The silicon oxide surface after each step of the fabrication process was observed and evaluated by images obtained from the scanning electron microscope. By applying voltage biases across the electrodes, the currents were measured in the dark and under illumination using a 375-nm laser. It was found that a constant photocurrent increment can be obtained for different voltage biases, and the nanodevice structure with a longer length had less conductivity but a larger increment of photocurrent after illumination. In addition, the efficiency rate of photocurrent generation is much higher in comparison to that obtained from CdSe thin film. The fabrication process integrated a newly developed model of a diode-resistor array of semiconductor-metal junctions between CdSe and Au NPs (nano-Schottky-diode structures), which can successfully explain the measured results. While nanotechnology has unprecedented advantages over the traditional silicon electronics, its technology presents physical challenges. However, the success of the fabrication of the multilayered photosensing nanodevice directly on the silicon chip paves the way for further applications and research.