Analytical and numerical models for Scanning Field-Emission Microscopy and their experimental validation

Scanning Field Emission Microscopy with Polarization Analysis (SFEMPA)

“…Details of these simulations and their results are discussed in Ref. [18]. Generally, our simulations found that very few excited electrons were able to escape the tip-target junction (actually almost none): after excitation just underneath the tip apex, the strong electric field used to extract the primary beam from the tip is found to bend the excited electrons toward the target.…”

“…In the Fowler-Nordheim regime, instead, the size of the primary beam and its characteristics are strongly dependent on the sharpness of the tip, so that particular care must be dedicated to its preparation. The larger the radius of curvature of the tip, the broader is the width of the primary beam [18] (in Ref. [19] a tip radius of less than 5 nm is observed in Transmission Electron Microscopy).…”

“…For efficient spin detection the energy of the electrons scattering at K should be in the 50 keV range, as explained later. We have used [18] COMSOL Multiphysics™ to design the electronoptical column, to simulate the trajectory of the electrons and to optimize the electrostatic parameters for conveying as many electrons as possible to the scattering target. We have found it appropriate to divide the handling of secondary electrons into two components, the Junction-Component and the System-Component.…”

Scanning tunneling microscopy in the field-emission regime: Formation of a two-dimensional electron cascade

“…Partial spectra shown as homogeneously colored curves represent electrons reaching the detector after a given number of re-entries into the solid, as indicated in the legend. experimentally distinguish between the tip current and the absorbed current; 12 (2) the achievable lateral resolution is of the order of a nanometer; 6,12 (3) significant contrast is observed at surface locations consisting of different elements; (4) magnetic signal has been observed on magnetized samples using a Mott-detector. 4,13 To understand the observed contrast as described above, it should be recalled that a change in the work function of the solid sensitively influences the secondary electron yield, leading to contrast governed by the chemical state of the surface.…”