Hybridization of Ellipsometry and Energy Loss Spectra from XPS for Bandgap and Optical Constants Determination in SiON Thin Films

Author: João Resende
Co-Authors: David Fuard, Delphine Le Cunff, Jean-Herve Tortai, Bernard Pelissier*

DOI: 10.1002/smll.202007344


In this study, we first compare the bandgap determination methods in SiON thin films using two established techniques: Ellipsometry and the Energy Loss Spectrum from X-ray Photoelectron Spectroscopy. In the ellipsometry case, we modelled the optical properties using a single Tauc-Lorentz oscillator model, in a range from 1.5 to 6 eV, while for the XPS case, we used the threshold energy of the Energy Loss Spectrum from the O1s and N1s main core levels to determine the bandgap. We observed a consistent difference of the energy bandgap values obtained between the two methods, reaching up to 1.6 eV.

Therefore, we combined the ellipsometry and Energy Loss Spectrum from XPS measurements, creating a hybrid metrology method using a triple Tauc-Lorentz oscillator model. This methodology respected the optical relations of each technique and the complex dielectric constant of the material, creating an overlap of the two measurements between 3.5 and 6 eV. The combination method brings the advantage of a more robust determination of the bandgap in the SiO2–Si3N4 system, while creating a way to measure the refractive index and coefficient of extinction for intermixed thin films of SiON, from 1.5 up to 30 eV.

Link: Hybridization of ellipsometry and energy loss spectra from XPS for bandgap and optical constants determination in SiON thin films - ScienceDirect

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