Photodetectors fabricated from a self-assembly of a deoxyguanosine derivative

A metal–semiconductor–metal (MSM) photodetector has been fabricated using as the semiconductor, a self-assembled layer of a DNA basis, namely a deoxyguanosine derivative, deposited between two gold electrodes. These were defined lithographically on a ${\mathrm{SiO}}_{\mathrm{2}}$ substrate, separated by a distance of about 120 nm. The resulting self-assembled guanosine crystal has been deposited in such a way to achieve striking semiconducting properties. We show that with these conditions, the I–V characteristics are independent of the crystal orientation. The device shows a high current response (differential resistance at room temperature ranges in MΩ) which is symmetric with respect to bias sign and dependent on the illumination conditions. This behavior can be explained by taking into account the standard MSM theory and its applications as a photodetector.