Two-component nanorod arrays by glancing-angle deposition.

A scalable strategy for three-dimensional (3D) assembly of dissimilar materials with nanometer resolution is key to harness the full potential of physical properties expected within the quantum-confined or interface-dominated size regime. Chemical synthesis methods yield layered and coaxial nanowires and branched nanocrystals, while physical vapor deposition (PVD) techniques are particularly effective in creating nanometer-scale structures along the growth direction perpendicular to the substrate. However, despite various successes in nanopatterning research, lateral (inplane) nanostructuring remains a great challenge. Here we report a method to fabricate arrays of nanorods with laterally stacked components. This technique, termed simultaneous opposite glancing-angle deposition (SO-GLAD), builds on conventional glancing-angle deposition, which uses variable deposition angles to engineer (single-component) 3D nanostructures including nanopillars, zigzags, nanospirals, nanotubes, and branched nanocolumns. During SO-GLAD, two different materials are deposited simultaneously from oblique angles from opposite sides onto self-assembled regular nanosphere arrays. Atomic shadowing causes selective deposition only on the side that is exposed to the deposition flux, leading to nanorod growth where each rod consists of two laterally separated components. This is demonstrated by the growth of 220-nm-wide Si–Ta twocomponent rods which exhibit a measured vertical interface width of 28 nm. This value is in good agreement with our theoretical prediction based on a purely geometrical analysis, suggesting that nanodesign at considerably smaller length scales is possible. SO-GLAD provides a new path to build uniquely shaped multi component nanostructures from a wide range of materials systems that are joined in a single deposition process. Figure 1a illustrates the SO-GLAD technique: materials A and B, which are in our case Si and Ta, respectively, are simultaneously deposited from oblique deposition angles a, onto a substrate which exhibits surface mounds that are, in our case, defined by silica spheres. We assume, in agreement with previous studies and the experimental observations