Fundamentals and applications of spectroscopic ellipsometry

Abstract

Recebido em 1/8/01; aceito em 8/11/01 This paper describes the use of ellipsometry as a precise and accurate technique for characterizing substrates and overlayers. A brief historical development of ellipsometry and the basic principles necessary to understand how an ellipsometer works are presented. There are many examples of studies performed in addressing materials science issues, and several are presented here: measurements of thickness, optical properties, and modeling of surface roughness. These selected results obtained in our laboratory for substrates, Si/SiO 2 interfaces, and polymers provide evidence that ellipsometry can play a critical role in characterizing different types of materials.Keywords: ellipsometry; polarization; films. BRIEF HISTORICAL OVERVIEWEllipsometry (reflection ellipsometry) measures the changes in the state of polarization of light upon reflection from a surface. The fact that changes are measured rather than the absolute intensity of light renders ellipsometry sensitive to submonolayer surface coverage. As a non-invasive and non-destructive tool, ellipsometry requires only a low-power light source and, consequently, it does not affect most processes, which renders ellipsometry a convenient tool for in situ studies 1,2 . P. Drude 3 was the first to build an ellipsometer even before Rothen has coined the word 'ellipsometry ' in 1945 4 . The equipment built by Drude is surprisingly very similar to many types of instruments in use today. Except for sparse papers, this technique received little attention for several decades after Drude, but in the 1970's and 1980's, ellipsometry became widely utilized, and relevant technical papers [5][6][7] and a classical book 8 were produced during this period. In 1991, Azzam compiled a considerable number of papers on ellipsometry 9 . As a search of the literature indicates, the number of papers on experimental improvement of ellipsometers has been decreasing in the last years, because many of the problems that existed before the advance of computers have been solved, including measurement speeds and spectral range. Most of the equipment used today is automated with wide band light sources, scanning monochromators, optical multichannel analyzers, and interfaces with acquisition and analysis software. Early studies on ellipsometry were performed using single wavelength equipment, usually a wide band visible light source with a filter, and later lasers. However, spectroscopic ellipsometers are commonly used nowadays in different research fields. BASIC CONCEPTSA description of ellipsometry as an optical technique would not be complete without mentioning J.C. Maxwell (1831-1879). Maxwell's theory predicts that light is a wave represented by two mutually perpendicular vectors: E, the amplitude of the electric field strength, and B, the amplitude of the magnetic field strength, and both E and B are also perpendicular to the direction of propagation, z. The electromagnetic wave is described by its amplitude and frequency in complex form:where E ...

Broad-Spectrum Anti-Adhesive Coating Based on an Extracellular Polymer from a Marine Cyanobacterium

“…For the proof of concept of CyanoCoating, gold substrates (Au) were used due to its suitability for surface characterization techniques [20]. CyanoCoating, and a coating using the reference material, medical grade polyurethane (PU), were covalently bound through a polydopamine (pDA) layer that was directly polymerized onto the Au substrates.…”

Broad-Spectrum Anti-Adhesive Coating Based on an Extracellular Polymer from a Marine Cyanobacterium

“…For the proof of concept of CyanoCoating, gold substrates (Au) were used due to its suitability for surface characterization techniques [20]. CyanoCoating, and a coating using the reference material, medical grade polyurethane (PU), were covalently bound through a polydopamine (pDA) layer that was directly polymerized onto the Au substrates.…”

Direct Observations of Surface Plasmon Polaritons in Highly Conductive Organic Thin Film

“…Besides, ellipsometric data, Δ and tan Ψ, 36 which include the information of changes in the polarization state of light reflected from the PEDOT:PSS films, were measured by spectroscopic ellipsometry. For each sample, three different areas were selected for measurements and inversion calculations.…”

Spectroscopic ellipsometry as a complementary tool for studying luminescent polymers: Poly(p-phenylenevinylene) as a particular case

“…The same procedure was used for analyzing the SE results for MH-PPV and MD-PPV films. This methodology is known as a multiple sample analysis, which has been frequently used for analyzing absorbing polymer films by SE [9]. The values of n as a function of the wavelength are shown in Fig.…”

“…The real (ε 1 ) and imaginary (ε 2 ) parts of ε can be expressed as ε 1 ¼ n 2 À k 2 and ε 2 ¼ 2nk [9], and the values of ε 1 and ε 2 for the films converted at different temperatures are shown in Values of n at an incident photon energy of 290 nm (4.9 eV) (where k is much lower than n), and relative area obtained from the FTIR spectra at 964 cm À1 for PPV films converted at different temperatures. temperature, 230 C, and practically constant values for energies higher than 3.2 eV.…”

Broad-Spectrum Anti-Adhesive Coating Based on an Extracellular Polymer from a Marine Cyanobacterium

“…For the proof of concept of CyanoCoating, gold substrates (Au) were used due to its suitability for surface characterization techniques [20]. CyanoCoating, and a coating using the reference material, medical grade polyurethane (PU), were covalently bound through a polydopamine (pDA) layer that was directly polymerized onto the Au substrates.…”

Direct Observations of Surface Plasmon Polaritons in Highly Conductive Organic Thin Film

“…Besides, ellipsometric data, Δ and tan Ψ, 36 which include the information of changes in the polarization state of light reflected from the PEDOT:PSS films, were measured by spectroscopic ellipsometry. For each sample, three different areas were selected for measurements and inversion calculations.…”

Spectroscopic ellipsometry as a complementary tool for studying luminescent polymers: Poly(p-phenylenevinylene) as a particular case

“…The same procedure was used for analyzing the SE results for MH-PPV and MD-PPV films. This methodology is known as a multiple sample analysis, which has been frequently used for analyzing absorbing polymer films by SE [9]. The values of n as a function of the wavelength are shown in Fig.…”

“…The real (ε 1 ) and imaginary (ε 2 ) parts of ε can be expressed as ε 1 ¼ n 2 À k 2 and ε 2 ¼ 2nk [9], and the values of ε 1 and ε 2 for the films converted at different temperatures are shown in Values of n at an incident photon energy of 290 nm (4.9 eV) (where k is much lower than n), and relative area obtained from the FTIR spectra at 964 cm À1 for PPV films converted at different temperatures. temperature, 230 C, and practically constant values for energies higher than 3.2 eV.…”

Broad-Spectrum Anti-Adhesive Coating Based on an Extracellular Polymer from a Marine Cyanobacterium

“…For the proof of concept of CyanoCoating, gold substrates (Au) were used due to its suitability for surface characterization techniques [20]. CyanoCoating, and a coating using the reference material, medical grade polyurethane (PU), were covalently bound through a polydopamine (pDA) layer that was directly polymerized onto the Au substrates.…”

Direct Observations of Surface Plasmon Polaritons in Highly Conductive Organic Thin Film

“…Besides, ellipsometric data, Δ and tan Ψ, 36 which include the information of changes in the polarization state of light reflected from the PEDOT:PSS films, were measured by spectroscopic ellipsometry. For each sample, three different areas were selected for measurements and inversion calculations.…”

Spectroscopic ellipsometry as a complementary tool for studying luminescent polymers: Poly(p-phenylenevinylene) as a particular case

“…The same procedure was used for analyzing the SE results for MH-PPV and MD-PPV films. This methodology is known as a multiple sample analysis, which has been frequently used for analyzing absorbing polymer films by SE [9]. The values of n as a function of the wavelength are shown in Fig.…”

“…The real (ε 1 ) and imaginary (ε 2 ) parts of ε can be expressed as ε 1 ¼ n 2 À k 2 and ε 2 ¼ 2nk [9], and the values of ε 1 and ε 2 for the films converted at different temperatures are shown in Values of n at an incident photon energy of 290 nm (4.9 eV) (where k is much lower than n), and relative area obtained from the FTIR spectra at 964 cm À1 for PPV films converted at different temperatures. temperature, 230 C, and practically constant values for energies higher than 3.2 eV.…”