Low energy electron microscopy (LEEM) has developed into one of the premier techniques for in situ studies of surface dynamical processes, such as epitaxial growth, phase transitions, chemisorption and strain relaxation phenomena. Over the last three years we have designed and constructed a new LEEM instrument, aimed at improved resolution, improved diffraction capabilities and greater ease of operation compared to present instruments.
Thermal adatoms (present on the surface at elevated temperature, in equilibrium with the step edges) are of key importance in dynamic phenomena such as step capillary wave motions, epitaxial growth, surface phase transitions, and the decay of nonequilibrium structures by surface diffusion. Here we present the first direct measurements of the thermal adatom concentration on Si(001) at elevated temperatures, from which we determine an adatom formation energy of 0.35 6 0.05 eV. Comparison with first-principles theory shows that the adatoms occur as dimers. These observations have direct implications for our understanding of surface diffusion and epitaxial growth.[S0031-9007(98)06726-X]
In this letter we describe a method for producing large areas of Si(001) surfaces which are (i) free of atomic steps and (ii) arranged in regular patterns on the wafer. The first step is the fabrication of a two-dimensional grating structure using e-beam lithography and reactive ion etching. This grating is then annealed within the appropriate temperature window in ultrahigh vacuum to produce the desired array of (001) step-free regions. We illustrate the success of the method through the use of low-energy electron microscopy for a few repeat spacings on test structures each extending over a 3×3 mm2 area. Alternative processing steps are discussed as well as application to submicron device technology.
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