Abstract

Inhomogeneities in the composition and microstructure as a function of depth in thin film coatings, whether intentional or unintentional, strongly influence their performance in a variety of applications including optical coatings, electrochromics, and photovoltaics. Spectroscopic ellipsometry has proven to be a very useful technique for characterizing such property gradients.¹ With ex situ measurements, however, the available data are insufficient to handle continuous gradients with high resolution. In our work, we have solved this problem by collecting ellipsometric data continuously versus wavelength and time during film growth. By applying this real time spectroscopic ellipsometry (RTSE), we have extracted continuous microstructural gradients having complex profiles with ~10 Å depth resolution, at the same time determining the instantaneous deposition rate and the evolution of the surface roughness layer thickness. Although the approach has been first demonstrated for characterizing intentional void volume fraction gradients in the window layers used for thin film photovoltaic devices, it has wider generality in a variety of other thin film coatings applications.

© 1995 Optical Society of America