Monitoring growth of ultrathin films via ion-induced electron emission

${\mathrm{H}}^{+}$, ${\mathrm{He}}^{+}$, and ${\mathrm{N}}^{+}$ ions with energy of $25\mathrm{keV}$ are scattered under a grazing angle of incidence from a clean and flat Cu(001) surface during deposition of ultrathin Co films. Making use of the ion-induced emission of electrons allows us to monitor growth of thin films via simple measurements of target current or from energy spectra of emitted electrons. The method provides excellent signals and is also applicable in the regime of poor layer growth.

Figure 1

Normalized intensity (lower panel) and target current (upper panel) as function of Co coverage on Cu(001) for scattering of $25\mathrm{keV}$ ${\mathrm{He}}^{+}$ ions under ${\Phi }_{\mathit{in}}=1.6°$. Gray curve: growth temperature $300\mathrm{K}$, black curve: $243\mathrm{K}$.

Figure 2

Normalized intensity of emitted electrons as a function of electron energy for impact of $25\mathrm{keV}$ ${\mathrm{He}}^{+}$ ions on $\mathrm{Co}∕\mathrm{Cu}\left(001\right)$ under ${\Phi }_{\mathit{in}}=1.6°$ for different Co coverages.

Figure 3

Normalized intensity of electrons (energy $145\mathrm{eV}$) as a function of Co coverage for impact of $25\mathrm{keV}$ ${\mathrm{H}}^{+}$ (dashed curve), ${\mathrm{He}}^{+}$ (solid curve), and ${\mathrm{N}}^{+}$ ions (dotted curve) from $\mathrm{Co}∕\mathrm{Cu}\left(001\right)$ film under ${\Phi }_{\mathit{in}}=1.6°$. Lower solid curve: intensity of specularly reflected ${\mathrm{He}}^{+}$ ions.

Figure 4

Upper panel: Normalized intensity of emitted electrons (energy $100\mathrm{eV}$) as a function of Co coverage for impact of $25\mathrm{keV}$ ${\mathrm{H}}^{+}$ ions under ${\Phi }_{\mathit{in}}=1.6°$ from $\mathrm{Co}∕\mathrm{Cu}\left(001\right)$ film grown at $140\mathrm{K}$. Lower panel: Same, but for specularly reflected ions. Inset: enlarged scale.