Field-emission and field-ion microscopy studies were carried out on (001)-oriented single-crystal tips. Facets of low-index planes, (001), {011} and {111}, were observed after heating a tip to high temperatures. The field-emission current fluctuations from thermally cleaned tips were larger than those of W field emitters. Field-emission patterns were found to depend upon the local curvatures of the tip surface.

Field-Emission and Field-Ion Microscopy of Lanthanum Hexaboride. Futamoto, M., Hosoki, S., Okano, H., Kawabe, U.: Journal of Applied Physics, 1977, 48[8], 3541-6