PC driven etching system for emitter needle tips

The reproducible forming of emitter needle tips is a serious demand for the fabrication of liquid metal ion sources. The movement of the needle into the etch solution, for tungsten 1n NaOH is used, a PC driven step motor with an increment of 2 µm is used. Due to the adjustment of the motion as a function of height and time the optimum shape of the tip can be repeatable etched. This process is controlled on a monitor optically using a long distance microscope and a video system. Characteristic needle tips with a radius of a few micron are presented.