Optical characterization of textured SnO2:F layers using spectroscopic ellipsometry

Abstract

The SnO2:F transparent conductive oxide (TCO) layers with submicron-size textured structures have been characterized using spectroscopic ellipsometry (SE). By applying the Drude model to the SE analysis, the optical carrier concentration, mobility, and sheet resistance of the textured SnO2:F layers have been estimated, in addition to the detailed layered structures. The excellent agreement has been observed between the results obtained from SE and other characterization techniques including scanning electron microscope, atomic force microscope, and Hall measurements, confirming that SE is a reliable measurement technique even for the textured structures. Nevertheless, the electron mobility obtained from SE is lower than that deduced electrically from the Hall measurement, although the carrier concentrations estimated from these techniques are quite similar. From the SE analysis, the optical constants of the textured SnO2:F layers have been extracted, and the free carrier absorption in the SnO2:F layers increases drastically with decreasing optical mobility. The SE technique developed in this study can be applied further to perform the nondestructive mapping characterization of large-area TCO textures incorporated into thin-film solar cell modules.