Fabrication of Non-Uniform Nanolattices with Spatially Varying Geometry and Material Composition

The fabrication of periodic 3D nanostructures with uniform material properties has been widely investigated and is important for applications in photonics, mechanics, and energy storage. However, creating nanostructures with spatially varying lattice geometry and material composition is still largely an unexplored challenge in nanofabrication. This work presents the fabrication of non-uniform nanolattices by patterning multiple layers of 3D nanostructures using phase shift lithography and atomic layer deposition. By controlling the processing parameters, the lattice geometry and material composition of each individual nanolattice layer can be tailored to create arbitrary material property profiles. Using the proposed method, a five-layer nanolattice with spatially varying porosity and oxide materials has been demonstrated. This process can be used to create gradient-index antireflection nanostructures, and a fabricated four-layer nanolattice structure consisting of TiO₂ and Al₂O₃ with gradually varying porosity reduces more than 90% of the specular reflectance from a silicon substrate. By enabling nanolattices with arbitrary profiles in physical properties, the demonstrated technique can find broad applications in nanophotonics, graded filters, energy storage systems, and nanoarchitected films.