Structural and multispectral characterization of AlScN thin films for quasi-BIC metasurface sensors

Scandium doping provides a feasible strategy to enhance the performance of aluminum nitride for optical and electromagnetic devices while retaining the material’s excellent structural integrity. In this study, Al _{1 -x} Sc _x N thin films were fabricated by radio frequency (RF) magnetron co-sputtering. The regulatory effects of scandium doping on the films’ morphology, optical constants, and terahertz dielectric properties were systematically investigated, and an AlScN-based metasurface structure was designed to validate its application potential. Structural characterizations confirmed that all films maintained a wurtzite crystal structure with a strong c-axis preferred orientation. Notably, an optimal scandium doping concentration suppressed abnormal grain growth, reduced surface roughness, and yielded denser and flatter film morphologies. Spectroscopic measurements demonstrated that scandium doping enabled monotonic modulation of the films’ complex dielectric constant, accompanied by tailorable dielectric loss characteristics, and enhanced the material’s optical dispersion capability. The simulated AlScN-based metasurface sensor exhibited high-quality-factor resonance with a quality-factor (Q-factor) of nearly 3000 as well as high sensitivity, which verifies its great application prospects in optoelectronic devices. This study clarifies the synergistic modulation mechanism of scandium doping on the multifunctional properties of AlScN thin films, provides critical optical and dielectric parameters together with simulation-based validation, and lays a solid foundation for the development of advanced optoelectronic and electromagnetic devices.