Atomic-Level Studies of Processes on Metal Surfaces

Abstract

An atomic-level understanding of surface phenomena is becoming increasingly important as materials scientists and engineers begin to fabricate new materials by controlling their growth at the nanometer or subnanometer scale. Recent advances in molecular beam epitaxy and chemical vapor deposition make it possible to assemble a crystalline solid or epitaxial overlayer literally one atomic layer at a time. The need to characterize the structure and composition of these complex materials in finer and finer detail has forced the traditional analytical tools (e.g., electron microscopy) to strive for better and better spatial resolution. It has also generated a virtual explosion in the proliferation of scanning probe microscopies inherently capable of viewing surface structure at the atomic level. This same need has recently rekindled an interest in the technique that first allowed scientists to view a solid surface in atomic detail: the field ion microscope (FIM). The unique attributes of this instrument and its successor, the atom probe mass spectrometer, make it possible to observe individual atoms on a solid surface, to remove atoms from the surface one atomic layer at a time, and to determine the chemical identity of the atoms as they are removed. The close match between these capabilities and the requirements of modern-day materials analysis have stimulated renewed efforts to use the FIM to gain fundamental insight into materials problems. This article discusses a few selected applications of the FIM, individually and combined with the atom probe, to phenomena occurring at the surface of solid materials.