The Influence of Deposition Rate on the Structure and Morphology of Gold/Silicon(111) Growth by Molecular Beam Epitaxy

ABSTRACT

The effect of deposition rate on the structural and morphological properties of thin gold films is reported with characterization by scanning tunneling microscopy and X-ray diffraction. The epitaxial growth of Au films on Si(111) 7 × 7 substrates was performed by molecular beam epitaxy under ultrahigh vacuum. The changes in the morphological properties of deposited films were monitored when the deposition rate was varied from 0.15 to 4.3 nm/min. The crystallographic structure of the films was assessed by X-ray diffraction. The grain size increased with the deposition rate and reached a maximum of 112.5 nm at 1.6 nm/min. At higher deposition rates, the grain size and the lattice strain slightly decreased. The flatness of the films was assessed by scanning tunneling microscopy under ultrahigh vacuum at room temperature. At the optimal deposition rate of 1.6 nm/min, the film was very smooth (0.02 nm). At lower or higher deposition rates, the roughness was increased. These results show that the quality of the film strongly depended on this parameter. The optimal roughness, thickness, and grain size occurred at a deposition rate of 1.6 nm/min.

KEYWORDS:

• Deposition rate
• gold thin film
• molecular beam epitaxy
• scanning tunneling microscopy
• X-ray diffraction