Performance of a low-voltage high-current-density electron probe

A low-voltage high-current-density electron probe has been constructed. Electrons are extracted at 7 kV from a zirconiated tungsten thermal field emission source, pass through a two-lens collimated optical system, and are decelerated by a retarding field at the sample. A focused probe is obtained at 1-keV landing energy with 40- nm diameter and 320-nA current. The corresponding peak current density is 1.3 × 10⁴A/cm². This result shows, for the first time, that space-charge beam broadening is much better controlled in these retarding field probes than in conventional low-voltage column designs where the extraction and landing energies are equal.