Spectroscopic ellipsometry of composite thin films with embedded Bi nanocrystals

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Abstract
8 pages, 6 figures, 1 table.-- PACS: 78.66.Jg; 78.66.Nk; 78.20.Ci; 68.55.Ln; 07.60.Fs; 81.05.Ys; 68.55.JkSpectroscopic ellipsometry together with an effective medium model is used to determine simultaneously the effective refractive index, thickness, and metal volume fraction of thin nanocomposite films. The films are formed by Bi nanocrystals embedded in amorphous matrices, either semiconducting (Ge) or dielectric (Al2O3). For the Bi:Ge films (metal in an absorbing host), the values obtained for both the real and imaginary parts of the refractive index vary continuously from that of Ge to that of Bi. The metal contents determined from the ellipsometry analysis are in excellent agreement with those obtained from direct measurements of the composition. For the Bi:Al2O3 films (metal in a nonabsorbing host), the extinction coefficient (k) exhibits a maximum around 360 nm which is related to the metal plasmon resonance frequency of Bi nanocrystals. The metal content determined from the ellipsometry analysis in this case is underestimated, probably due to interaction of the Bi crystals with the Al2O3 host.This work has been partially supported by CICYT\ud (Spain) under TIC96-0467 project. The authors are grateful\ud to the GPS (Université de Paris VI et VII, France) for provision\ud and assistance of Rutherford backscattering facilities.\ud One of the authors (J.M.B.) greatly acknowledges a FPI\ud grant from the Spanish Ministry of Education and Culture.Peer reviewe