Some Observations on Low-Temperature Field-Ion Microscopy

The operation of a He-ion microscope immersed in a liquid H2 cryostat is shown to be feasible and to lead to ultrahigh vacuum before, during, and after microscopy, thereby facilitating experiments in which surface contamination must be avoided. Measurements of ion current at various temperatures are reported and discussed. The variation of end form with field evaporation temperature for tungsten from 200°–600°K is shown to lead to local field enhancement in the (100) region at high temperature, partly because of increased local disorder.