Sacrificial-layer atomic layer deposition for fabrication of non-close-packed inverse-opal photonic crystals

A method is presented for predicting and precisely controlling the structure of photonic crystals fabricated using sacrificial-layer atomic layer deposition. This technique provides a reliable method for fabrication of high-quality non-close-packed inverse shell opals with large static tunability and precise structural control. By using a sacrificial layer during opal infiltration, the inverse-opal pore size can be increased with sub-nanometer resolution and without distorting the lattice to allow for a high degree of dielectric backfilling and increased optical tunability. For a 10 % sacrificial layer, static tunability of 80 % is predicted for the inverse opal. To illustrate this technique, SiO₂ opal templates were infiltrated using atomic layer deposition of ZnS, Al₂O₃, and TiO ₂. Experimentally, a static tunability of over 600 nm, or 58 %, was achieved and is well described by both a geometrical model and a numerical-simulation algorithm, When extended to materials of higher refractive index, this method will allow the facile fabrication of 3D photonic crystals with optimized photonic bandgaps.