Optical and structural properties of co-sputtered Cu-Si-O and Cu-Ge-O thin films (Presentation Recording)

The co-sputtered Cu-Si-O and Cu-Ge-O thin films were prepared using reactive DC, pulse DC and modulated pulse power magnetron sputtering (MPPMS) on two separate Cu and Si or Cu and Ge targets simultaneously. The powers on each target and Oxygen/Argon flow ratio f(O2) were varied to have different stoichiometies determined by XPS. The film thickness, refractive index n and extinction coefficient k were extracted from in situ ellipsometry and the reactive plasma discharge was monitored by optical emission spectroscopy in real time during film growth. The grazing incident x-ray diffraction measurements reveal that the films deposited at low f(O2) have the nanocrystalline structure of cuprous Cu2O with diffraction peaks of (111) and (200). The films deposited at high f(O2) (≥ 1) have cupric oxide CuO phase. The optical constant n and k, film density and band gap of the co-sputtered film were investigated and determined by in situ ellipsometry, X-ray reflectivity and UV-Vis-NIR spectroscopy. Their structural, chemical and optical properties are able to be tuned by incorporating Cu2O, CuO and the mixtures of them into Silicon oxide or Germanium oxide matrix with varying target powers and oxygen/Argon ratio for applications in optical coatings and optical filters.