Field emission characterization of vertically oriented uniformly grown nickel nanorod arrays on metal-coated silicon substrate

摘要

Vertically oriented, densely packed Ni nanorod arrays have been fabricated on metal-coated Si substrate via cost-effective electrochemical technique. Directional growth of the nanorods is performed through the nanopores of anodic alumina membrane via electrodeposition process. Al_2O_3 membrane is removed at the final fabrication step by wet-etching process to get vertically-standing nanorods on Si wafer. Electron microscopic images depict the growth of highly ordered, uniformly grown Ni nanorods with diameter around 50 nm. These types of vertically aligned uniform nanorods supported by Si substrate have very good applications in sensors and field emission displays. Closer look of the electron microscopic images show very sharp tips, which provide large field enhancement and, therefore, are particularly suitable for field emission applications. Field emission studies of the nanorods are performed with standard diode configuration with sample as cathode and a stainless steel tip as anode under high vacuum. Field emission current as a function of applied field shows considerable electron emission with low threshold field around 5 V/μm. The field emissionrndata are found to be well-fitted with linear Fowler-Nordheim plot, indicating the cold field emission mechanism in our samples. Calculation of the geometrical field enhancement factor (β) of the as-synthesized nanorod tip is found to be around 3690, which is sufficient to enhance the macroscopic field at the emitter tip and, hence, supplies the required barrier field (also called local field at the 'emitter-tip) to produce low-threshold cold field electron emission. Therefore, the cost-effective synthesis of vertically aligned Ni nanorods supported by Si substrate can be used as a field emission device for potential low power panel applications.