Monolayer graphene film on ZnO nanorod array for high-performance Schottky junction ultraviolet photodetectors.

A new Schottky junction ultraviolet photodetector (UVPD) is fabricated by coating a free-standing ZnO nanorod (ZnONR) array with a layer of transparent monolayer graphene (MLG) film. The single-crystalline [0001]-oriented ZnONR array has a length of about 8-11 µm, and a diameter of 100∼600 nm. Finite element method (FEM) simulation results show that this novel nanostructure array/MLG heterojunction can trap UV photons effectively within the ZnONRs. By studying the I-V characteristics in the temperature range of 80-300 K, the barrier heights of the MLG film/ZnONR array Schottky barrier are estimated at different temperatures. Interestingly, the heterojunction diode with typical rectifying characteristics exhibits a high sensitivity to UV light illumination and a quick response of millisecond rise time/fall times with excellent reproducibility, whereas it is weakly sensitive to visible light irradiation. It is also observed that this UV photodetector (PD) is capable of monitoring a fast switching light with a frequency as high as 2250 Hz. The generality of the above results suggest that this MLG film/ZnONR array Schottky junction UVPD will have potential application in future optoelectronic devices.

Metal-oxide-Semiconductor capacitors fabricated by layer-by-layer nanoassembly and microfabrication.

Metal oxide semiconductor (MOS) capacitors were fabricated by electrostatic layer-by-layer self-assembly (LbL-SA) combined with a modified lift-off technique. The MOS capacitors were built on both n-type and p-type silicon substrates. The numbers of silicon dioxide (SiO2) nanoparticle layers were varied to characterize the electrical performance of MOS capacitors. Unlike the conventional process, LbL-SA allows us to deposit the thin films for a semiconductor device with a lower temperature, lower cost, and shorter processing time. The stability of the silica insulation layers was also investigated. Atomic force microscopy (AFM) served to monitor the film quality of the self-assembled thin films.