Polarization-dependent differential reflectance spectroscopy for real-time monitoring of organic thin film growth

A Navarro-Quezada,Th Wagner,P Zeppenfeld,E Ghanbari,M Aiglinger

doi:10.1063/1.4936352

A Navarro-Quezada, Th Wagner + Show 3 more

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https://doi.org/10.1063/1.4936352

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Abstract

By monitoring the reflectance of a sample surface during deposition of a thin organic film, one can obtain information with submonolayer resolution in real-time. A special kind of optical spectroscopy is Differential Reflectance Spectroscopy (DRS), which compares the reflectance before and during deposition of a thin film or any other change of the surface optical properties. In this work, we present an extended DRS setup that allows monitoring simultaneously both linear polarization states (s and p) of the reflected light. We implement polarization-dependent DRS to monitor the growth of perflouropentacene thin films on a Ag(110) single crystal. The setup allows us to deduce the optical anisotropy of the sample and, in particular, the preferred orientation of the molecules on the surface.

Highlights

Optical spectroscopy is a non-destructive, powerful technique which is commonly applied to monitor physical processes occurring at surfaces and interfaces in situ and in real-time
In order to verify the stability of the acquired signal over time, we present in Fig. 4 the signal transients for both polarization states of light at 2.1 eV
We have presented a polarization-dependent Differential Reflectance Spectroscopy (DRS) setup

Summary

INTRODUCTION

Optical spectroscopy is a non-destructive, powerful technique which is commonly applied to monitor physical processes occurring at surfaces and interfaces in situ and in real-time. Proehl et al pointed out the possibility to use polarized light while monitoring the reflectance during deposition of PTCDA on different substrates In their analysis, they found it not necessary to consider the exact experimental geometry at θ = 20◦ and discriminated between the different polarizations states (s and p), because they found no significant influence on the DRS signal for the entire absorption range of their specific organic molecule.. We observe significant polarization-dependent changes in the reflectance during the deposition, related to the different optical transitions excited by the two linear polarization states of light. From these results, we can obtain important information on the alignment of the molecules on the Ag(110) surface. The present study demonstrates the advantages of employing pol-DRS as a tool for in situ monitoring organic thin film growth

EXPERIMENTAL

RESULTS

CONCLUSIONS