Two-dimensional growth of Al films on Si(1 1 1)-7 × 7 at low-temperature

Morphology and structure of the Al(1 1 1) films, grown on Si(1 1 1)-7 × 7 surface at both low (145 K) and room temperature, are investigated by in situ reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). In the low-temperature case, a well-defined critical thickness of 4 ML, at which atomically flat Al films with remarkable stability form, is identified. The formation of the flat film at the critical thickness completes the Al/Si(1 1 1) interface, and results in a subsequent homoepitaxial-like layer-by-layer growth for the entire Al coverages studied. The results are consistent with the formation of the quantum well states (QWS) recently observed in this system, and typify another intriguing example of quantized electronic states in tailoring thin film growth.