In 1985, Ernst Bauer and his student Wolfgang Telieps published a stunning set of images that abruptly solved a long-debated question in surface science: What is the nature of the phase transition that occurs on the (111) surface of silicon? 1 Determining the complex ordered arrangement of atoms, or “reconstruction,” that occurs there had been one of the hottest problems in surface science for nearly 25 years. 2 One of their images (see figure 1) shows a sharply defined coexistence between two structural phases and demonstrates a first-order—rather than a continuous second-order—transition between an ordered (bright) and disordered (dark) arrangement of atoms at the surface. Bauer and Telieps’s unambiguous answer about the nature of that disordering transition dramatically introduced a very powerful probe of solid surfaces: low-energy electron microscopy (LEEM).
Since publication of those early images, an increasing number of investigators have used LEEM to gain insights into a...
