Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

We present an introduction into the basics of light matter interaction, photospectroscopy and spectroscopic ellipsometry of thin films. Starting with the nature and description of polarized light, the interaction of light with matter in form of reflection, absorption and transmission and the physical effects leading to this behavior are shown. The optical constants, refractive index and extinction coefficient are derived and combined to a single complex parameter. This complex refractive index will be compared and connected to the dielectric function which describes the electric field inside a medium. It is shown that the dielectric function can be described by a sum of light driven oscillator motions of electric dipoles inside a medium. Fundamental different dielectric functions are related to optical and electrical behavior for dielectrics, semiconductors and metals.
To measure the behavior of light incident on a medium, photospectroscopy and spectroscopic ellipsometry is introduced. With photospectroscopy the intensity of reflected, transmitted and absorbed light can be measured. Here different measurement setup for specular and diffuse light is presented and major issues discussed. Complementary to photospectroscopy spectroscopic ellipsometry measures the change of the phase relation of s and p polarized light after the interaction with matter. This technique is very sensitive to various material properties like film thickness, roughness, interfaces, composition, crystallinity, stress and many more. It is shown how an ellipsometer retrieves data and how this data is used to model the dielectric function. Key aspects discussed are analysis procedures, the necessity of model building and fitting together with walk through steps and examples.