DETERMINATION OF THE DIELECTRIC CONSTANT OF CdS BY ELLIPSOMETRY, INTERFEROMETRY AND BY OPTICAL EXCITATION OF SURFACE PLASMONS

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DETERMINATION OF THE DIELECTRIC CONSTANT OF CdS BY ELLIPSOMETRY,

INTERFEROMETRY AND BY OPTICAL EXCITATION OF SURFACE PLASMONS

M. Abraham, A. Mahmoudi, A. Tadjeddine, J. Rolland

To cite this version:

M. Abraham, A. Mahmoudi, A. Tadjeddine, J. Rolland. DETERMINATION OF THE DIELECTRIC

CONSTANT OF CdS BY ELLIPSOMETRY, INTERFEROMETRY AND BY OPTICAL EXCITA-

TION OF SURFACE PLASMONS. Journal de Physique Colloques, 1983, 44 (C10), pp.C10-119-C10-

122. �10.1051/jphyscol:19831025�. �jpa-00223482�

JOURNAL DE PHYSIQUE

Colloque CIO, supplément au n°12, Tome M, décembre 1983 page C10-119

DETERMINATION OF THE DIELECTRIC CONSTANT OF CdS BY ELLIPSOMETRY/

INTERFEROMETRY AND BY OPTICAL EXCITATION OF SURFACE PLASMONS

M. Abraham, A. Mahmoudi, A. Tadjeddme and J.P. Rolland

Département de Physique, Université d'Oran, Algeria

*L.E.I. du C.N.R.S., 1, -place A. Briand, 92195 Meudon, France

Résumé - Trois méthodes complémentaires (ellipsométrie, intérférométrie et excitation des plasmons de surface) sont utilisées pour déterminer la constante diélectrique de films de CdS déposés sur un substrat d'argent entre 700 et 450 nm.

Abstract - Three complementary methods, ellipsometry,inter- ferometry and surface plasmon (SP)excitation, are used to de- termine the dielectric constant of CdS deposited on a silver substrate over the wavelength range 700-450 nm

1 Samples : the substrate used in our studies was a 0.6ym silver film deposited onto polished quartz plates.We evaporated the CdS films onto the silver. The film for ellipsometric studies Bias evaporated onto a substrate preheated at 200°C and was 1.3um thick. For SP Studies the films were thinner, 15-20 nm, and were deposited onto the substrate at ambient. Structural studies using X rays and electron microscopy have shown that the samples are well crystallised in a hexagonal structure with the C axis perpendicular to the surface of the sample .

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measurements were carried out using an ellipsometer without compensator,following the ideas and procedures outlined pre- viously (1).

In the region tf u) > Eg where the thickness of the CdS layer is large compared with the penetration depth for the radiation, the sample can be considered as semi-infinite and consequently the experimental para- meters allow the direct calculation of the complex dielectric constant of the semiconductor.

In the region )( D< Eg, the el lipsometric measurements can no longer be used because of the. oscillations produced by interferences, A (~ 90°) and i> (~ 20°) .

3 Interference_method : if .it is assumed that e = 0 in the region tf a) < Eg, the phase condition leading to an extremum in the interferen- ce can be written as follows (2) :

(1) where 0 is the phase difference between two consecutive reflected beams, 0 is the phase difference introduced by reflection at the CdS / Ag interface, cp is the angle of incidence and d is the thickness of the CdS film.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19831025

C10-120

JOURNAL DE PHYSIQUE

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R e f e r e n c e s

( 1 ) ABRAHAM M., MAHMOUDI A. a n d TADJEDDINE A . , E x p e r i m . T e c h n . P h y s . , t o b e p u b l i s h e d . ( 2 ) BORN M. a n d WOLF E . , P r i n c i p l e s o f O p t i c s

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( 3 ) G R I G O R O V I C I R . , T h i n S o l i d F i l m s

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( 4 ) CARDONA M . g n d HARBEKE G .

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( 7 ) HOPFIELD J . J . a n d THOMAS O.G., P h y s R e v . x ( 1 9 6 3 ) 5 6 3