Resolving power of lens-less low energy electron point source microscopy

Simulations show the resolving power of lens-less low energy electron point source microscopy to be approximately 15 A for electron energies of between 14 and 105 eV. This resolution can be improved to 10 A by employing a composite hologram method. However, these values fall short of predictions of at least 3 A resolution for electron energies in this range because the limited divergence angle of the electron beam had not previously been taken into account. Also shown is that electron coherence from field emitting tips that terminate in a single atom will not limit the resolving power as much as the beam divergence angle. The penetration depth of electrons with energies of between 50 and 100 eV, into biological molecules, was estimated from the inelastic mean free path length to be 25 A . This places an upper limit on the size of biological molecules for which internal structural information can be obtained using low energy electrons.