Growth and evolution of epitaxial erbium disilicide nanowires on Si (001)

Sub-monolayer amounts of Er deposited onto Si(001) react with the substrate to form epitaxial nanowires of crystalline ErSi2. The growth of uniaxial structures occurs because the different crystal structures of ErSi2 and Si have a good lattice match along one Si<110> crystallographic axis but a significant mismatch along the perpendicular Si<110> axis. The nucleation, growth, and subsequent evolution of ErSi2 nanowires were investigated as functions of erbium coverage on the Si (001) surface, annealing time, and annealing temperature. Low annealing temperatures (620 degreesC) and times (5 min) produced ErSi2 nanowires with widths of a few nanometers, heights less than one nanometer, and lengths of several hundred nanometers. For longer annealing times at low temperature, the surface roughened without significant ripening of the wires. Annealing at intermediate temperatures (similar to 700 degreesC) caused stacking faults to form along the long axis of the nanowires and their lengths to ripen. At high temperature (800 degreesC), the wires broke apart into short segments with stacking faults.