Designing bent silicon crystals via coactive thin-films for high energy beam manipulation

Thin film stress offers a scalable and contact-free approach for inducing controlled and tunable bending in silicon crystals, with direct relevance for bent crystal channeling and related beam manipulation applications. In this work, stress evolution of silicon nitride films deposited by low pressure chemical vapor deposition (CVD) and inductively coupled plasma CVD, thermally grown silicon dioxide (SiO2), and titanium nitride (TiN) thin films deposited by reactive magnetron sputtering on silicon (Si) substrates is systematically investigated as a function of film thickness. Silicon nitride films exhibit an approximately linear stress-thickness dependence, leading to strong bending at small thicknesses, followed by a gradual reduction in bending efficiency with increasing film thickness. Thermally grown SiO2 behaves as an approximately constant-stress system, resulting in a stable and predictable curvature response. In contrast, TiN films exhibit exponential stress relaxation with thickness, enabling significant curvature even at small thicknesses. By combining experimentally calibrated stress-thickness relations with practical film thickness limits, this work establishes a predictive framework linking material choice, film thickness, and substrate geometry to achievable bending radii for representative channeling and beam manipulation applications.