Epitaxial growth of Ag films on native-oxide-covered Si substrates

By employing radio-frequency magnetron sputtering, cube-on-cube domain epitaxy of silver films was accomplished on the Si(001) substrates that were initially covered with native silicon oxide. Energetic bombardment by sputtered Ag particles was found to play a critical role in the epitaxial growth, enabling desorption of native oxide at temperatures significantly lower than that reported in conventional thermal annealing in ultrahigh vacuum. Native oxide was found to desorb at temperatures as low as $200°\mathrm{C}$ as a result of kinetic interaction with the deposition flux. At deposition temperatures of $550°\mathrm{C}$ or above, native oxide was completely removed from the Si surface, and the grown films showed strong epitaxial relationship, $\mathrm{Ag}\left(001\right)\left[110\right]∕∕\mathrm{Si}\left(001\right)\left[110\right]$. X-ray photoemission spectroscopy analysis confirmed that the desorbed silicon oxide migrated to the top surface of the Ag layer during sputter deposition.

Figure 1

(Color online) (a) XRD $\theta ∕2\theta$ scan profiles of Ag films that were sputter deposited for $40\mathrm{s}$ at different temperatures ($200°\mathrm{C}$, $350°\mathrm{C}$, $400°\mathrm{C}$, and $550°\mathrm{C}$) on the Si(001) substrates initially covered with native oxide. (b) Pole figures from the $550°\mathrm{C}$ sample: the Ag(111) poles (top) and the Si(111) poles (bottom).

Figure 2

SEM images of Ag films deposited at $550°\mathrm{C}$ for $40\mathrm{s}$ (a), $50\mathrm{s}$ (b), and $60\mathrm{s}$ (c).

Figure 3

XPS analysis results of the Ag films that were deposited at room temperature for $90\mathrm{s}$ (left-hand panel) and at $200°\mathrm{C}$ for $5\min$ (right-hand panel). The depth profiles of Ag, O, and Si concentrations are shown in the top panel. The energy spectra of Si and Ag measured at the film-substrate interface are shown in the bottom panel. Note the different energy ranges used for the spectra.

Figure 4

XPS analysis result of a Ag film deposited at $550°\mathrm{C}$ for $90\mathrm{s}$. (a) Depth profiles of Ag, O, and Si concentrations. (b) Depth profiles of Si $2p$ energy spectra. (c) Depth profiles of O $1s$ energy spectra.

Figure 5

XRD $\theta ∕2\theta$ scan profiles of the Ag films remaining on Si substrates after the film removal process. The Ag films were deposited for $40\mathrm{s}$ at $300°\mathrm{C}$, $350°\mathrm{C}$, $400°\mathrm{C}$, or $550°\mathrm{C}$. The inset shows a magnified view in the Ag(002) peak region of the $300°\mathrm{C}$ sample after the film removal process (empty square). The XRD before film removal is also shown for comparison (filled circle).