Starting from 1st Fabruary 2015 SOPHi@webinar platform has been moved to CHEETAH webinar platform
in date 22/05/2014

Extraction of refractive index data from optical measurements of flat, rough and inhomogeneous thin films

 

R & T determinationThe webinar launched in the frame of SOPHi@Webinar and 7FP-CHEETAH project concerns the introduction to the procedure based on the transfer-matrix method (TMM) utilized @ HZB to extract optical parameters in thin film for PV. The procedure is available in request

 

 

 


Useful information

Abstract

The refractive index of a material is not directly accessible to experiments, yet it can be extracted using optical measurements of transmission T and reflection R of a thin layer. Often times this extraction is performed based on physical models that need to be chosen carefully according to the specific material type. During the webinar, however, the speakers presented a  procedure based on the transfer-matrix method (TMM) that allows the exclusive mathematical recalculation of the complex refractive index (n,k) from measured (T,R). The extended model cannot only  be applied to flat thin films but it can also address common imperfections of thin layers like surface roughness or internal roughnesses (voids), which usually destroy the applicability of the TMM. The according simulation tool RefDex, which was developed based on this procedure,  is very useful particularly for the characterization of multilayer stacks including roughnesses


Agenda


Details

Extraction of refractive index data from optical measurements of flat, rough and inhomogeneous thin films

Speakers : SCHMID Martina

Unlike other physical parameters the refractive index of a material is not directly accessible to experiments. Yet, we can use optical measurements of transmission T and reflection R of a thin layer to extract its dielectric function. Often times this extraction is performed based on physical models that need to be chosen carefully according to the specific material type. Here we present a procedure based on the transfer-matrix method (TMM) that allows the exclusive mathematical recalculation of the complex refractive index (n,k) from measured (T,R). This means no particular material model for the film investigated is required. Moreover, we will address common imperfections of thin layers like surface roughness or internal roughnesses (voids), which usually destroy the applicability of the TMM, by adapting the model to consider these properties. By comparing (T,R) calculated as a function of the desired optical constants (n,k) with the measured data in an iterative minimization process of the deviation the desired dielectric function becomes accessible. This procedure under consideration of surface and internal roughnesses for a multilayer stack of thin films and thick substrates as well as with the option of an effective medium is possible via our simulation tool RefDex.


Presentation of hands-on examples

Speakers : MANLEY Phillip

After the  physical background presentation   of the simulations hands-on sample characterization has been presented  at the end of seminary