Home


Research 


Link


 
 

Home

  People   Laboratory   Publications  
 
 

Projects

  Thesis   Collaboration   Link  

                                                                   

Spectroscopic Ellipsometry facility             Optical Laboratory 

 

The Photonic Laboratory of the Dipartimento di Matematica e Fisica "Ennio De Giorgi" was born in 2008 in order to investigate the optical properties of a wide range of organic and inorganic materials.

 

Spectroscopic Ellipsometry facility

Introduction

Spectroscopic Ellipsometry (SE) is a powerful optical technique for the investigation of the dielectric properties (complex refractive index and dielectric constant) of thin films. This technique has become the state of the art standard to determine thin films thickness and optical constants  of all types of materials, including dielectrics, semiconductors, metals, and organics.

Beyond the determination of the complex refractive index of uniform materials SE is particularly powerful for the investigation of ultrathin layers (down to sub nanometric thickness), for the determination of the film roughness and of composition non-uniformity for materials and materials blends.

Our Service

Our laboratory offers a measurements service for customers needing a short term feedback on their thin films or multilayers properties.

Instrument and capabilities

Sopra ES4G variable angle spectroscopic ellipsometer

Spectral range 230-930 nm Angle of incidence range 0-45°
Maximum spectral resolution 0.05 nm at 313 nm Angle of incidence setting accuracy 0.01°
Repeatibility TanY ±0.001, cos0.0015  at 45° and 600 nm

Output

The output of the experiment is sample dependent and can include:

Refractive index dispersion (real and imaginary part) and film thickness  for single film and multilayers Dielectric constant dispersion (real and imaginary part) and film thickness  for single film and multilayers
Blends composition and kind of mixing for many materials Surface Roughness
Intermixing of materials of a multilayer Composition gradient

Materials

Dielectric and semiconductor bulk Conductive transparent oxides (ZnO, ITO etc)
Single thin film and multilayers Blends of different materials
Organic films, including monolayers and layer by layer and Langmuir Blodgett multilayers Photoresist layers
Metal films Transparent resins
Thin dielectic overlayers (including native oxides) Anti reflective coatings

up

Optical Laboratory

The optical laboratory is equipped for the investigation of the photoluminescence and optical gain of organic, nanocrystals and hybrid organic-inorganic systems (in collaboration with Dr Mauro Lomascolo of CNR-IMM of Lecce).

The experiments are performed both with Continuos Wave and Pulsed high energy UV excitation, as a function of the excitation density and of the sample temperature.

 

Set-up for the characterization of organic optical gas sensors (c/o CNR-IMM Lecce). Two optical fibers are used for the laser excitation of the film and for the PL collection. The chemical composition of the chamber atmosphere is controlled by mixing dry air with the different analytes (In collaboration with  Dr. R. Rella of CNR-IMM Lecce)

 

Organic blue emitting waveguide with optical gain. The active film is about 300 nm thick and, in the measurement conditions, emits 3ns stimulated emission pulses with a 10 Hz repetition rate. (Click on the image for a video)

 

 

PL spectra in the 0-1 spectral region of a polyfluorene film as a function of the excitation density. The spectra are normalized to 1 for clarity. It is evident the progressive increase of the 470 nm ASE band, together with the blue-shift of both ASE band, and the spectral rebroadening of the 478 nm band for excitation densities higher than about $350 Jcm^{-2}$. These effects are due to gain saturation.

Copyright (2008)  American Institute of Physics.The paper can be downloaded for personal use only. Any other use needs the autorization of the author and of the American Institute of Physics.The paper has been published in Applied Physics Letters 93, 123311 (2008)

β/glassy-phase relative Amplified Spontaneous Emission threshold as a function of the relative waveguide losses and of the β-phase content of the film. The thickest line is the line of equal ASE threshold of glassy and β-phase samples.

 Copyright (2008) American    Institute of Physics.    The paper can be downloaded for personal use only. Any other use needs the autorization of the author and of the American Institute of Physics.The paper has been published in Applied Physics Letters 93, 023308 (2008)

 

up