【Other Papers】Νon-destructive quantification of fill factor and thickness of GaN nanowire layers formed via nitridation of Ga₂O₃ nanowires

      Researchers from Aristotle University have published a dissertation titled " Νon-destructive quantification of fill factor and thickness of GaN nanowire layers formed via nitridation of Ga₂O₃ nanowires " in Applied Surface Science.

Abstract

      GaN nanowire networks combine a direct band gap with a high surface-active area. Quantitative evaluation of the surface area is directly associated with the fill factor of the nanowire layer, defined as the fraction of the total layer volume occupied by the nanowires. However, conventional porosimetry methods are not suitable due to the extremely small pore dimensions. In this work, β-Ga₂O₃ nanowires grown on Si and fused SiO₂ were converted into GaN nanowires under a flow of NH₃, yielding networks of randomly oriented nanowires. Complete conversion was achieved at high NH₃ flow rates and nitridation temperatures above 800° C. The high surface-to-volume ratio of the polar nanowires gives rise to Raman-active surface optical (SO) phonons, whose frequencies depend on the effective dielectric environment. Their dependence on the fill factor was calculated and used to extract the fill factor values from Raman spectra. These values were then incorporated into X-ray Fluorescence (XRF) analysis to determine the actual thickness of the GaN nanowire layer. Fill factors between 0.3 and 0.7 correspond to layer thicknesses between 0.4 and 1.4 μm. The combined Raman-XRF approach provides a non-destructive and scalable method for determining the fill factor and thickness of III-V semiconductor nanowire networks.

DOI：

https://doi.org/10.1016/j.apsusc.2026.167669