Atomic-Scale Resolution on the MgO(100) Surface by Scanning Force and Friction Microscopy

Abstract

MgO(100) surfaces have been imaged at atomic-scale resolution by scanning force and friction microscopy (SFFM). The single crystals of MgO were cleaved and studied in dry air using a small loading force (4 * lo-'' N). Topographic and friction images reveal a square lattice of protrusions with a measured spacing of 0.274 nm. This value is close to the 2D surface lattice parameter of the MgO(100) surface (0.299nm). The largest corrugation observed in the topographic images is 0.04 nm. Large-scale images reveal nearly parallel cleavage steps, separated by an average distance of 150 nm and 0.4 nm high.

Models of image contrast in scanning force microscopy on insulators

“…An early example of such a model has been that of one atom tip apex and rigid surface. A 'contact hard sphere' approximation was used for interpretation of SFM images obtained in air and in ultrahigh vacuum (UHV) in which a rigid surface composed of hard spheres with ionic radii was profiled by another hard sphere representing the tip apex atom [31][32][33][34]. However, it was soon recognized that the tip and surface deformation, and even wear during scanning in contact can be very significant [35].…”

Fabrication techniques and material properties of dielectric MgO thin films—A status review

“…Steps of the vacuum-cleaved surfaces are found to run over distances of the order of a micron and to be separated by 10-400 nm. Perrot et al [45] derived similar conclusions by AFM on MgO h1 0 0i surfaces, which are cleaved and studied in dry air. They observe 0.4 nm high steps separated by an average distance of 150 nm.…”

Study of the Nature and Distribution of Elementary Steps on the (100) Cleavage Faces of MgO Single Crystals by Atomic Force Microscopy

“…Cleavage steps of heights of a/2 (IKEYAMA et al 1966) and a (PERROT et al 1994) have been reported on the (100) planes of MgO crystals. Here a is the lattice parameter equal to 0.421 nm.…”

“…During recent years there is an increasing interest in the investigation of the surface morphology of cleavages of a variety of ionic single crystals (LANGFORD et al 1990;OVERNEY et al 1992;SEO, SHINDO 1994;PERROT et al 1994;IKEMIYA et al 1996), using techniques like atomic force microscopy (AFM) and scanning tunnelling microscopy. In the case of MgO crystals, AFM studies reveal mono-, bi-and trilayer steps (PERROT et al 1994;IKEMIYA et al 1996;KIM, BAIK 1995) as well as multilayer steps of height up to 40-50 nm on their cleavages (KIM, BAIK 1995;SANGWAL et al 1997a).…”