Optical properties of solid thin films by spectroscopic reflectometry and spectroscopic ellipsometry.

The intense focus on the development of practical optoelectronic and photonic devices demands accurate characterization of the optical properties of the materials of interest.

Some of these materials include zinc oxide (ZnO), strontium titanate (STO) and gold nanoparticles.

It is envisioned that these materials will be best utilized in thin film technology.

Spectroscopic reflectometry (SR) and spectroscopic ellipsometry (SE) are uniquely powerful tools for accurately characterizing the optical properties, structure and thicknesses of thin films.

Combining both techniques in one measurement offers many advantages, not the least of which is reduced systematic errors from the simultaneous analysis of multiple data sets.

We report for the first time, the use of SR and SE concurrently (SRSE), to successfully develop optical models, and determine the variation in refractive index, n and extinction coefficient, k above and below the band edge of ZnO, for thin films deposited on silicon and platinum substrates at various deposition temperatures.

For the first time, a graded layer model is used to model the surface roughness layers to give extremely accurate fits to the data on Pt substrates.

We also report the development of an optical model based on reflectometry data, for STO films deposited on silicon and platinum at various substrate temperatures.

The analysis reveals an index gradient in STO deposited on silicon and no interface layer as reported in other publications.

Finally, we were able to successfully model, using SRSE data, the optical properties of molecularly mediated, self-assembled gold nanoparticle thin films.

The analysis reveals that n and k increase with the thickness of the thin films with the same linking molecule and that for similarly sized Au nanoparticles, the decrease in the chain length of the linker molecules results in higher values of n and k.