Self-organized metal networks at ion-etched Cu∕Si and Ag∕Si interfaces

Abstract

We report self-organized metal nanopatterns on Si substrates produced by ion beam etching. We have deposited thin layers of metal such as Cu or Ag on Si substrates and then etched the deposited layers by a 1–5keV Ar+ ion beam at room temperature. At the stage when the metal-Si interface is reached, we have observed networks of metal clusters on the Si substrate with the characteristic size of 30–60nm for Cu and 100–200nm for Ag. The Cu patterns are sensitive to the ion energy. At 1keV energy, we observe a well-defined Cu network, whereas at 3–5keV energy, the Cu pattern becomes fuzzy without clear boundaries. To systematize and explain our results, we have suggested a kinetic model that combines ion etching and coarsening of the metal clusters on Si substrates. From our kinetic Monte Carlo simulations, we have found that the cooperative effect of coarsening and etching has a regime when the size of metal clusters can be approximated by the expression a(4D∕aR)1∕3, where D is the surface diffusivity of metal adatoms on the Si substrate, R is the etch rate, and a is the interatomic distance. Our synergistic model of coarsening and sputtering explains the observed difference in Cu and Ag cluster sizes and predicts the fuzzy Cu patterns at elevated ion energies.