Fabrication of a sharp molybdenum tip by combining electrostatic-stress-driven pull-up growth and build-up process

Abstract Electrostatic stress-driven pull-up growth (EPG) and build-up processes were integrated to develop a method for sharpening the tip of polycrystalline Mo wires. In EPG, the Mo-wire tip was softened through laser-heating and subsequently subjected to voltages ranging from 0 kV and −27 kV. Consequently, the tip was pulled upward due to electrostatic stress, thereby sharpening it. At −15 kV, the tip was surrounded by facets with a minimum curvature radius of 121 nm. In the build-up process, the Mo-wire tip sharpened in EPG was laser-heated multiple times at a voltage of −15 kV, with the laser output 2 W lower than that used in EPG. On the tip, high-surface-energy facets shrunk and low-surface-energy facets expanded, rendering the tip sharper with a minimum tip curvature radius of 35 nm. This paper also discusses the potential applicability of the proposed method to bcc metals other than Mo.