Fabrication and Atomistic Modeling of Ion-Etch Nanostructures on Substrates
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Fabrication and Atomistic Modeling of Ion-Etch Nanostructures on Substrates Maria Stepanova and Steven K. Dew Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4, Canada ABSTRACT We have implemented and investigated numerically a new process to fabricate selforganized metal networks and lines on non-metallic substrates. We have deposited a thin film of Cu on silicon and glass substrates and etched the film by a 1 keV-energy Ar beam. Due to the kinetic mechanism known as sputter instability, nanosize metal patterns self-organize on the substrate at the stage when the etched surface reaches the metal/substrate interface. By numerical simulations, we have investigated the mechanism and control factors for the process.
INTRODUCTION Arrays of nanosize metal dots, metal networks and nanowires on nonmetallic substrates have a strong potential as nonlinear electronic and optoelectronic modules and storage nodes for nanocrystal memories. However, non-lithographic fabrication of metallic patterns on substrates presents a major challenge because, as a rule, metallic nanostructures cannot be grown by conventional heteroepitaxy similarly to semiconductor quantum dots. In this work, we report a simple two-stage process to fabricate self-assembled networks of Cu dots and lines on Si and SiO2 substrates employing etching by a neutralized ion beam. Our process employs the known effect of sputter instability, which generates self-organized mounds or ripples when a surface is ion-bombarded [1]. In brief, when a surface is exposed to a beam of atomic particles, these deposit their energy at the surface. Some of the surface atoms that have acquired the deposited energy are emitted (sputtered). The local amount of deposited energy, and therefore the number of emitted atoms, is sensitive to the surface curvature. Surface atoms are emitted preferentially from hollows, whereas emission from tops of mounds is inhibited, which leads to self-organized morphologies [1-7]. We employ this effect to fabricate metallic patterns on non-metallic substrates. We deposit a thin Cu film on silicon and glass substrates and etch the film by a neutralized Ar beam in a standard ion mill system until the etched surface approaches the substrate, as sketched in Fig. 1. This produces self-organized Cu patterns on the substrate. We investigate properties of the Cu patterns and control factors over the process.
Figure 1. Fabrication of self-assembled patterns on substrates.
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Figure 2. SEM images of Cu patterns on Si at normal incidence (a), on glass at normal incidence (b) and on glass at 82° incidence (c). The arrow in (c) shows the projection of the Ar beam on the surface.
Figure 3. High-resolution 200nm×200nm SEM image of the Cu pattern on glass at normal incidence.
EXPERIMENT For substrates, we used Prime Si (100) wafers and 0211 glass wafers. The substrates were cleaned in hot solution 75% H2SO4:25% H2O2 for 15 min. 50-nm thick Cu films were deposited on the substrates with
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