Process-dependent optical properties of Al nanotriangle arrays modified by oblique deposition and post-annealing

Localized surface plasmon resonances in aluminum nanostructures are highly sensitive to nanoscale geometry and metal–emitter separation, both of which can be modified by fabrication processes. In this study, we investigate process-dependent optical properties of Al nanotriangle arrays fabricated by nanosphere lithography, focusing on the effects of oblique deposition and post-annealing on optical absorption and photoluminescence behavior. Oblique deposition induces anisotropic growth of Al nanotriangles, resulting in closely spaced dimer-like configurations that enhance lateral interparticle coupling and activate hybridized plasmonic modes. In contrast, post-annealing induces optical changes that are consistent with oxide-related surface modification of Al, including a possible reduction in the effective plasmonic volume and an increase in the effective metal–emitter separation. Optical absorption measurements reveal systematic size- and process-dependent resonance shifts. These trends are qualitatively interpreted using finite-difference time-domain simulations based on simplified models incorporating effective size reduction and representative interparticle proximity. Photoluminescence and time-resolved spectroscopy demonstrate that emission enhancement is governed by a competition between lateral interparticle coupling and annealing-induced changes in the effective metal–emitter interaction. While narrow interparticle gaps enhance near-field coupling, excessive proximity can promote nonradiative energy transfer. The present study provides process-oriented insights into plasmon-enhanced emission in Al–Alq 3 plasmon-emitter systems. • Optical properties of Al nanotriangle arrays modified by oblique deposition and annealing • Interparticle coupling and annealing-induced surface modification affect plasmonic resonances • Simplified FDTD simulations capture size- and gap-dependent plasmonic trends • Emission enhancement governed by competition between interparticle and metal-emitter distances • Annealing-induced optical changes provide insight into Al-based plasmonic emission systems