APL Photon. 1, 021301 (2016)

Scanning electron microscopy (SEM) is a useful and well-established tool for characterizing nanoscale samples, but comes with limitations. For example, the size of the electron beam varies with the beam current and surface charging issues can occur when imaging samples that are electrical insulators. Now, Gediminas Seniutinas and co-workers have shown that light from an ultraviolet (UV) light-emitting diode can be used to improve material contrast and resolution during SEM experiments. The UV light from the diode generates electrons from the sample surface via the photoelectric effect and these usefully contribute to the imaging, enabling a faster acquisition rate. The authors state that UV illumination also reduces distortions related to surface charging, to the extent that metal coating may not be required. In this work, the authors used a diode emitting light at 260 nm, which corresponds to a photon energy close to the work function of materials such as Ti, Au and Al. The authors thus demonstrated material-dependent contrast not only via secondary electron generation, but also due to differences in work function or photoelectric-generated charges.