Correlations between In Situ Conductivity and Uniform-Height Epitaxial Morphology in Pb/Si(111)-(7×7)

Area of Science:

• Surface Science
• Materials Science
• Condensed Matter Physics

Background:

• Understanding thin film growth is crucial for semiconductor technology.
• Lead (Pb) deposition on silicon (Si) surfaces is a model system for studying epitaxial growth and wetting phenomena.
• Previous studies on Pb/Si(111) focused on structural properties, with less emphasis on electrical transport at low temperatures.

Purpose of the Study:

• To investigate the electrical resistivity of Pb films grown on Si(111)-(7×7) at low temperatures (72–201 K).
• To correlate electrical transport properties with structural evolution during film growth.
• To elucidate the mechanisms behind unusual resistivity behavior observed during Pb deposition.

Main Methods:

• In situ electrical resistivity measurements were performed during Pb deposition.
• Scanning tunneling microscopy (STM) was used to characterize the surface morphology and film structure.
• Variable temperature measurements were conducted to analyze the temperature dependence of resistivity.

Main Results:

• An anomalous 'hump' in specific resistivity (ρ) versus coverage (θ) was observed for temperatures above 140 K.
• This unusual behavior correlated with the formation of uniform, eight-layer Pb islands.
• Superdiffusive motion of the wetting layer was identified as a contributing factor to the observed resistivity anomaly.

Conclusions:

• The study reveals a novel electrical transport regime in Pb films grown on Si(111) at low temperatures.
• A quantitative model considering the film resistivity as a series combination of an amorphous wetting layer and crystalline islands successfully explains the experimental data.
• The findings provide insights into the interplay between morphology, dynamics, and electrical properties during thin film growth.