Field Electron Emission from Molybdenum Tips: Preparation and Characterization

Abstract

Molybdenum is a transition metal, known for its coarse nature and high hardness. In the present study, a 99.95 % pure molybdenum material was used to fabricate nano- and micro-scale tips from wires that have a diameter of 0.1 mm. These tip samples were prepared using the electrochemical etching process with a chemical solution composed of methanol and sulfuric acid in a 7:1 ratio. This is a newly reported etching solution for the sample preparation technique that has been achieved with considerable difficulty. A very sharp and blunt molybdenum tips with different radii were obtained. The prepared samples have been characterized under high vacuum conditions with pressure below 10^-7 mbar. Field emission measurements of the very sharp tip showed that emitted electrons have been obtained at a low applied voltage of 850 V, with a 0.166 µA emission current recorded. The current continued to increase gradually until the applied voltage reached 1750 V, where the current reached 3.9 µA. The measured current-voltage characteristics of the tips were analyzed using Fowler-Nordheim theory and the Orthodoxy test.