On the importance of precise measurements of the optical properties of gold electrodes in LIMM/(F)LIMM

Abstract

Precise measurements of the optical properties of electrodes add value to the interpretation of the recorded current spectra when applying Laser Intensity Modulation Method (LIMM) for space charge density measurements, including also its version with focused laser ((F)LIMM). They allow to correctly account for the energy deposition in the metal electrode and in the dielectric material under study. In this work the refractive index (n) and the extinction coefficient (k) have been extracted from the recorded by spectroscopic ellipsometry spectra and then integrated in the model to account for the nature and real conditions of the electrode. Such approach improves modeling of the temperature required for extraction of the space charge. It is found that higher refractive indexes of the gold electrodes lead to an important increase of the signal/noise ratio, thus improving the sensibility of the method for space charge measurements. It also allows to probe much lower levels of space charge densities.