RT Journal Article
T1 Optical analysis of absorbing thin films: application to ternary chalcopyrite semiconductors
A1 Martil De La Plaza, Ignacio
A1 González Díaz, Germán
A1 Hernández Rojas, J.L.
A1 Lucía Mulas, María Luisa
A1 Sánchez Quesada, Francisco
A1 Santamaría Sánchez-Barriga, Jacobo
AB The refractive index n and the absorption coefficient-alpha of radio frequency sputtered CuGaSe2 and CuInSe2 thin films were obtained by means of transmissivity (T) and reflectivity (R) measurements at normal incidence. The optical properties were determined from the rigorous expressions for the transmission and the reflection in an air/film/(glass)substrate/air multilayer system. The solutions to this system of equations are not unique, and the physically meaningful solution is identified by trying different thicknesses in the numerical approach. Usually, nonacceptable n dispersion curves are found for all thicknesses. To be able to obtain a good n dispersion curve and, therefore, a correct absorption coefficient, we propose a simple modification of the equations for R and T through a factor called the coherence factor (CF). Because of the surface roughness and the nonuniformity of n and alpha, the light rays that reflect internally in the interface between the substrate and the film have a random difference in optical path. The CF accounts for this effect. This modification leads to an unambiguous and accurate determination of the optical properties and thickness of thin films for all wavelengths where transmission is not negligible. The CF is shown to be greatly dependent on the thickness of the film. This method can be used even when the R and T spectra do not have interference fringes. This method is applied successfully to the optical analyses, in the 0.4-2.5-mu-m wavelength range, of CuInSe2 and CuGaSe2 ternary chalcopyrite thin films deposited onto glass substrates by radio-frequency sputtering.
PB The Optical Society of America
SN 0003-6935
YR 1992
FD 1992-04-01
LK https://hdl.handle.net/20.500.14352/59312
UL https://hdl.handle.net/20.500.14352/59312
LA eng
NO © Optical Society of America. The authors thank J. Carabe (Instituto de Energías Renovables, Centro de Investigaciones Energéticas y Medio Ambientales) for optical measurement facilities and J.M. Gómez de Salazar (Departamento deMetalurgia, Universidad Complutense de Madrid) for the scanning electron microscope facilities.
DS Docta Complutense
RD 18 abr 2025