Ion beams and their applications in high-resolution probe formation

The most critical demand for high-brightness ion beams emerged from the realm of industrial applications of focused ion beams and it was met by using liquid metal ion source technology. Although recognized as a successful technology, liquid metal ion sources have major limitations in view of beam species. Noncontaminating ion beam species with beam brightness comparable to liquid metal ion source, i.e., ∼10⁶ A cm^-2 sr^-1 and energy spread of ∼1 eV will be ideal for many cutting-edge applications including ion beam milling, mask repair, and imaging studies. This paper attempts to bring out the essential points in the development of high-resolution probe forming beams. With this specific objective in view, this study is based on an analysis of point sources and then a variety of other sources, under the general classification of "broad" source (primarily plasma sources), are discussed. Several sources in this category including a Penning-type source, a multicusp source, and new-generation high-charged state sources seem to have merits for circumventing the limitations of liquid metal ion sources, although further research is needed to improve the beam brightness and advance the state-of-the art.