SURFACE SPECTROSCOPY WITH HIGH-SPATIAL-RESOLUTION USING METASTABLE ATOMS

THE study of surface phenomena is in large part dependent on spectrosc opic techniques that are sensitive to of only the outermost few layers of the material under consideration. A variety of such techniques are now available, some of which also have the benefit of high spatial re solution(1-3) Here we show that metastable atoms-that is, atoms in lon g-lived excited states-can be used as a sensitive surface probe with h igh spatial resolution. In contrast to electrons or photons, metastabl e atoms cannot penetrate into a solid; instead, they are de-excited re adily following interaction with the surface electronic orbitals(4,5). The de-excitation process is accompanied by the emission of electrons , the energy spectrum of which provides fundamental information about the electronic properties of the surface. High spatial resolution (in the present case, about 5 mu m) is achieved by detecting electrons tha t have been emitted from only a small area of the sample. As the metas table atoms have only thermal kinetic energies, they are essentially n ondestructive, making them ideally suited to probing fragile surfaces such as organic layers and biological specimens.