Preface: Cathode Lens Microscopy for Nanoscience

This issue of the IBM Journal of Research and Development describes several recent advances in the field of nanoscience, with an emphasis on cathode-lens-based microscopy methods, including low-energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM). Also discussed are related analytical approaches such as low-energy electron diffraction (LEED), thermionic electron emission microscopy (TEEM), mirror electron microscopy, and x-ray photoemission electron microscopy (X-PEEM). Briefly, a cathode lens is an electron optical arrangement in which the sample forms the cathode of an objective lens, resulting in a strong electrostatic field of approximately 100 kV/cm that accelerates low-energy electrons reflected or originating from the sample to a final energy range of 15–20 keV. This strong electrostatic field enables high spatial resolution in spite of the low electron energy values (0–100 eV) at the sample surface. The papers collected in this issue were all presented at the Seventh International Workshop on LEEM and PEEM, held from August 8 to 13, 2010, in Manhattan, and reflect the depth and breadth of the topics and issues discussed at the workshop. These papers highlight recent scientific advances, as well as instrumental developments on topics that include thin films, organic films, surface chemistry, magnetism, time-resolved methods, and novel applications of microscopy in material science. The initial six papers of this issue focus on a variety of instruments and methods. The first paper, by Schramm et al., describes LEEM and spectroscopy with the Leiden Electronic, Structural, and Chemical Nanoimaging in Real Time (ESCHER) system. The authors describe the layout and capabilities of a new aberration-corrected LEEM and PEEM facility, which features real-and reciprocal-space spectroscopy. Here, the authors present images of the first experiments performed with ESCHER focused on the growth of graphene on SiC(0001). Müllerová et al. discuss scanning transmission LEEM. In particular, the authors discuss an extension to the transmission mode of the cathode-lens-equipped scanning electron microscope, enabling operation down to lowest energy values of electrons. Penetration of electrons through freestanding ultrathin films is examined along the full energy scale, and contribution of the secondary electrons, released near the bottom surface of the sample, is shown to enhance the apparent transmissivity of the sample to above 100%. Experiments performed on graphene flakes and on a 3-nm-thick carbon film are used to demonstrate the method. Kennedy et al. present Laplacian and caustic imaging theories of a mirror electron microscopy work-function contrast. The authors simulate the mirror electron microscope (MEM) …