Advances in helium ion microscopy

With the advent of a reliable high brightness ion source, utilizing helium (He) as the ion species, a new branch of microscopy has emerged. The promise of sub-nm focused probe sizes coupled with the unique He beam/sample interactions has led to a range of both high resolution imaging and high fidelity material modification applications. However, realizing the full potential of the He ion source is not without its challenges. Some of the difficulties are presented, along with a discussion of a systematic effort to overcome these issues. This work has resulted in the ability to routinely take images with an edge resolution of 0.35 nm or better. The nature of the He ion beam interaction with the sample makes possible numerous diverse applications, beyond the high resolution imaging already mentioned. A few of these will be highlighted, including imaging insulating samples, scanning transmission He ion microscopy, and material modification. Finally an extension of the high source brightness technology to utilizing neon (Ne) as the ion species is described. The source properties are given, along with a calculation of the expected probe size from such a Ne ion source and column.