Comparison of optical models and signals from XPS and VASE characterized titanium after PBS immersion
Here we consider the optical and the chemical effects of a phosphate buffered saline (PBS), to titanium (Ti) surfaces. Compound (Ti, TiO, TiO2 and Ti2O3) analysis was conducted for native surfaces as well as for ultra pure water exposed and for PBS exposed sample surfaces using an X-ray photoelectron spectroscopy (XPS). The reflectance of surface's top layer was modeled by evaluating Bruggeman's model with the particular refractive index spectra. After the reflectance models were gathered, a diffractive optical elements (DOE) based sensor was used to determine coherent and non-coherent reflectance from the Ti samples, while the Ti surfaces were immersed in water or in a PBS solution. The DOE measured samples were also characterized with a variable angle spectro-ellipsometer (VASE). Accordingly to the reflectance models, the oxidation of the titanium surface decrease the overall reflectance of the surface. However, the DOE sensor measurement showed also signals in which the reflectance was observed to increase. This increase of reflectance was interpreted to be caused by effective gas layer. Study also showed, that used PBS solution had similar chemical oxidation effects, and thus optical effects, to the titanium as used ultra pure water. (C) 2011 Elsevier B.V. All rights reserved.