Surface-directed Nanoepitaxy on a Surface with an Irregular Lattice.

Understanding and developing metrics on how nanocrystals respond to local external surface stimuli at their interfaces during growth or operation is a key step in advancing scalable and deterministic approaches for fabricating functional one- and two-dimensional (1D and 2D) nanoscale networks. Here, we present early results on a general approach for surface-directed nanocrystal epitaxy on a surface with an irregular lattice constant. We show that patches of lattice matched areas as small as 7 nm in a background of surface lattice disorder could satisfy the condition for epitaxial growth of a crawling nanocrystal over the disordered region. Threshold of failure in nanocrystal epitaxy is found to depend on the spacing between the patches and their total surface area. Results indicate nanoepitaxy on a disordered surface occurs if it contains patches of lattice matched regions with at least 20% of surface coverage, illustrating the remarkable tolerance of this type of growth to surface lattice disorder. By adjusting this threshold, it is possible to scalably restrict nanocrystal growth, filter out single nanowires and partition nanowire heterojunctions into segments with different orientations or modulate their electronic structures. This approach is expected to impact epitaxy of highly-mismatched semiconductors and lead to realization of ultrathin heterojunctions of 1D-2D materials.