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Field Emission Ion Sources for Focused Ion Beams
Published in Arthur T. Hubbard, The Handbook of Surface Imaging and Visualization, 2022
Field ionization is a process in which atoms are auto-ionized by a high electric field. The probability of ionization depends very strongly on the strength of the field, and an appreciable ionization rate can only be achieved for fields of the order of 1 V/Å(1010 V/M). Field evaporation is a similar process that involves the thermal desorption of an atom that is ionized as it leaves the surface or evaporation of an already created ion. The high fields necessary can be achieved conveniently by applying modest voltages, in the range 1 to 10 kV, to a very sharp needle called a field emitter. A field emitter is usually produced by an electrochemical etching technique. The end radius of a field emitter ranges from 100 nm, used when ions are produced from the gas phase, to 10 µm when ions are produced from the liquid metal phase. In the latter case the actual ion emitter is the surface of the liquid, which assumes a conical shape under the action of surface tension and the stress of the applied electric field. The end radius of a LMIS is only a few nanometers. Because the emitter radius is very small in both the gas phase and liquid phase cases, the ionization region is also quite small and the field emitter behaves like a point source of ions. As a result, the ion optical brightness of a field ionization source is very high: a brightness of the order of 1010 A/cm2 sr has been achieved with a GFIS. A brightness of ~ 106 A/cm2 sr is typical for LMISs.
Enhanced corrosion resistance of adhesive/galvanised steel interfaces by nanocrystalline ZnO thin film deposition and molecular adhesion promoting films
Published in The Journal of Adhesion, 2022
Richard Grothe, Jan Striewe, Dennis Meinderink, Thomas Tröster, Guido Grundmeier
Field emission scanning electron microscopy (FE-SEM) and focused ion beam (FIB) were performed using a NEON®40 electron microscope (Carl Zeiss AG, Germany) at a base pressure of below 10−9 bar equipped with a Schottky field emitting cathode. FE-SEM images were taken at a low acceleration voltage of < 2 kV. FIB cuts were made using a Ga liquid metal ion source (LMIS) with 6 kV acceleration voltage.