Two-dimensional layered perovskites (2DLPs) are non-conventional semiconductors that combine strong excitonic effects, intrinsic quantum confinement, and compositional tunability, making them promising materials for integrated photonics [1,2]. A key challenge for their implementation into photonic architectures is the fabrication of single microcrystal-based structures with controlled geometry and homogeneous quality, which are required for nanoscale patterning.

In response to this challenge, we developed a fast and reproducible recrystallization strategy to grow single crystalline 2DLP microcrystals with well-defined rectangular geometry, atomically flat surfaces, and controllable lateral sizes ranging from a few to several hundred micrometers. These microcrystals exhibit spatially homogeneous emission and act as open cavities that support confined photonic modes, fundamental for strong light-matter interaction [3]. Their high optical quality makes these microcrystals ideal platforms for deterministic nanofabrication, allowing the introduction of controlled features or defects to tailor light–matter interactions at the microscale and paving the way for potential monolithic integration into photonic circuits.

To achieve precise structuring, we optimized focused ion beam (FIB) milling as a nanofabrication technique for these soft materials. By systematically evaluating how ion dose and gallium implantation affect their optical properties, we defined a processing window that preserves emission while enabling accurate geometry control. Within this regime, individual microcrystals can be patterned into photonic-crystal or grating architectures, offering new routes to control light propagation directly within the crystal.

Enabling on-chip integration further requires electrical contacting of individual microcrystals. To this end, we adapted electron beam lithography by tuning the developer chemistry to prevent microcrystal dissolution, achieving reliable fabrication of metal electrodes directly on their surfaces.

By combining reproducible recrystallization, controlled ion-beam processing, and on-crystal lithography, we establish a robust toolbox for deterministic microstructure design and integration, allowing both active and passive photonic components to be integrated within a single perovskite-based photonic circuit