Lightweight Soft X-ray Shielding in β-Ga2O3-Coated Natural Wood Evaluated Using a Ga2O3 Schottky Barrier Diode Detector

Abstract

Soft X-ray shielding under stringent mass constraints is increasingly important for near-space aviation, small satellite platforms, and other weight-sensitive aerospace systems. Natural wood is an attractive lightweight and biobased structural core; however, its attenuation capability at keV range photon energies is strongly governed by bulk density. In this study, we enhance the soft X-ray shielding performance of natural wood by introducing a spray-deposited β-Ga₂O₃ particle-containing coating formed with a binder matrix. The transmitted X-ray intensity was quantified using a β-Ga₂O₃ Schottky barrier diode detector under 5.0 kVp irradiation. Three wood species with different bulk densities─cedar, oak, and birch, with densities of 0.289, 0.697, and 0.913 g·cm^–3, respectively─were prepared with a fixed thickness of 1 mm. Cross-sectional scanning electron microscopy and energy-dispersive X-ray spectroscopy reveal the formation of an approximately 100 μm thick near-surface wood–inorganic hybrid region, in which Ga and O signals coexist within the coated wood structure. Compared with uncoated wood, the β-Ga₂O₃-containing coating consistently reduces the transmitted X-ray-induced current for all wood species, leading to improved shielding efficiency. Notably, cedar, the lowest density wood, exhibits the largest relative improvement after coating, indicating that a thin inorganic coating can effectively compensate for the intrinsically limited attenuation of lightweight wood cores while imposing only a modest mass penalty. These results demonstrate a practical wood–inorganic composite architecture for lightweight soft X-ray shielding and suggest that low-density wood substrates can provide a favorable mass–performance balance when combined with β-Ga₂O₃-based surface hybridization.