Substrate Holder Material-Driven Microstructure Evolution and Hydrogenation Behavior of Pd/Mg Thin Films Prepared by Magnetron Sputtering

Mg-based thin films are promising candidates for hydrogen-responsive optical devices. However, their performance is strongly influenced by microstructural evolution during deposition. In this work, Mg thin films were deposited onto glass substrates placed on different substrate-holder materials (Si and 304 stainless steel) to investigate the influence of substrate-holder configuration on microstructure formation. Fluorocarbon (FC)/Pd/Mg multilayer films were subsequently fabricated to evaluate hydrogenation and dehydrogenation behaviors. The results show that the substrate-holder material significantly affects film morphology and hydrogenation performance. Mg films prepared using the Si holder exhibit relatively uniform hexagonal-like surface morphologies, whereas those prepared using the stainless-steel holder show a transition from granular to hexagonal-like morphologies with increasing sputtering power. Hydrogenation measurements reveal that FC/Pd/Mg films prepared using the stainless-steel holder exhibit superior performance, including a reflectance modulation of approximately 70%, a transmittance modulation exceeding 40%, and a hydrogenation time of about 30 s. In contrast, films prepared using the Si holder show reduced optical modulation and slower hydrogenation kinetics. The observed differences in hydrogenation behavior are closely correlated with variations in film microstructure induced by different substrate-holder configurations. The results suggest that substrate-holder-dependent growth conditions may influence defect formation and hydrogen diffusion pathways in Mg-based thin films. This study highlights the importance of substrate-holder configuration as a processing parameter affecting microstructure evolution and hydrogen-responsive performance in FC/Pd/Mg multilayer films.