A method of microtip fabrication based on oxygen induced faceting

The macroscopic W[1 1 1] tip facets and forms a truncated three-sided pyramid when annealed at 1400-1600 K after being exposed to about 1.3 Langmuir of oxygen. Further annealing of the tip in temperature range of 1000-1060 K leads to significant sharpening of the tip apex. FIM observations revealed that the apex consisted of several atoms at most. FEM images of such prepared tips suggest that they can be used as point sources of electrons.