Phase characterisation of TiO2 thin films using micro-Raman spectroscopy and glancing angle X-ray diffraction

It is possible to tune the refractive index (n) of a TiO₂ film to the optimum value for an encapsulated silicon solar cell by annealing the coating after deposition. Annealing causes a change in the volume fraction of rutile and this was examined as a function of annealing temperature for thin (∼70 nm) TiO₂ films on a silicon substrate using micro-Raman spectroscopy and glancing angle X-ray diffraction. Both techniques were able to monitor the progression of the phase change in the films. Micro-Raman spectroscopy provided a rapid means to monitor the phase change and could detect phase fractions below approximately 5%. Glancing angle X-ray diffraction provided quantitative results but the technique was considerably more time consuming. The results indicated that the refractive index varied linearly with the rutile phase fraction.