A Materials Engineering Approach to Enable Controlled Spalling for Material Agnostic Layer Transfer

Advanced electronics, photonics, and quantum systems increasingly demand bulk-quality thin films of semiconductor materials that are costly, hard to grow, or incompatible with one another. Conventional layer-transfer techniques face limits in thickness, thermal budget, crystal damage, and waste. This work evolves controlled spalling as a material-agnostic, low-temperature alternative that mechanically exfoliates a thin crystalline layer by driving a sub-surface crack parallel to the wafer surface using a tensile metal stressor. We study the fracture-mechanics foundations of spalling and identify two practical bottlenecks, reliable crack initiation and transient crack control. We then engineer processing solutions including robust seed layer adhesion, electroplated Ni stressors with optimized chemistry, and electrode designs to tame current crowding and tune thickness profiles, enabling repeatable stress and improved uniformity. We demonstrate controlled spalling of 4H silicon carbide, a notably hard, high-value substrate, using refined thickness control and engineered initiation. The spalled films preserve crystalline quality and support coherent control of native divacancy spin ensembles with coherence times that remain close to bulk, indicating suitability for heterogeneous quantum integration. Then the process is applied to yttrium iron garnet thin films, decoupling them from lossy substrates at cryogenic temperatures and enabling hybrid superconducting magnonic devices that exhibit clear photon-magnon hybridization, underscoring the integration benefits of removing the substrate. Our work then extends the approach to other challenging systems (e.g., sapphire, diamond), introduces practical initiation schemes and stress-elevating techniques, shows straightforward bonding and substrate reuse, and demonstrates spalling of prefabricated silicon carbide devices. Finally, we outline scaling tactics for large-area, single-front propagation using engineered stress profiles and mechanical biasing. Together, these results elevate controlled spalling to a versatile layer-transfer platform that lowers material cost, preserves bulk-like properties, and unlocks heterogeneous integration across power, photonic, and quantum technologies.