Compositionally Dependent Nonlinear Optical Bandgap Behavior of Mixed Anodic Oxides in Niobium?Titanium System
Sprache des Titels:
Englisch
Original Kurzfassung:
Optical bandgap mapping of Nb?Ti mixed
oxides anodically grown on a thin film parent metallic
combinatorial library was performed via variable angle
spectroscopic ellipsometry (VASE). A wide Nb?Ti compositional
spread ranging from Nb-90 at.% Ti to Nb-15 at.% Ti
deposited by cosputtering was used for this purpose. The Nb?
Ti library was stepwise anodized at potentials up to 10 V SHE,
and the anodic oxides optical properties were mapped along
the Nb?Ti library with 2 at.% resolution. The surface dissimilarities along the Nb?Ti compositional gradient were minimized by
tuning the deposition parameters, thus allowing a description of the mixed Nb?Ti oxides based on a single Tauc?Lorentz
oscillator for data fitting. Mapping of the Nb?Ti oxides optical bandgap along the entire compositional spread showed a clear
deviation from the linear model based on mixing individual Nb and Ti electronegativities proportional to their atomic fractions.
This is attributed to the strong amorphization and an in-depth compositional gradient of the mixed oxides. A systematic optical
bandgap decrease toward values as low as 2.0 eV was identified at approximately 50 at.% Nb. Mixing of Nb2O5 and TiO2 with
both amorphous and crystalline phases is concluded, whereas the possibility of complex NbaTibO
Forschungs-