Focused ion beam milling: A method of site-specific sample extraction for microanalysis of Earth and planetary materials

Argon ion milling is the conventional means by which mineral sections are t hinned to electron transparency for transmission electron microscope (TEM) analysis, but this technique exhibits significant shortcomings. In particul ar. selective thinning and imaging of submicrometer inclusions during sampl e milling are highly problematic. We have achieved successful results using the focused ion beam (FIB) lift-out technique, which utilizes a 30 kV Gaion beam to extract electron transparent specimens with nanometer scale pre cision. Using this procedure, we have prepared a number of Earth materials representing a range of structures and compositions for TEM analysis. We be lieve that FIB milling will create major new opportunities in the field of Earth and planetary materials microanalysis, particularly with respect to u ltraprecious mineral and rock samples.