Spectroscopic ellipsometry—A perspective

Aspnes, D. E.

doi:10.1116/1.4809747

Cited by 33 publications

(15 citation statements)

References 56 publications

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“…Principles and applications of SE are described at length in books [46][47][48] and recent reviews. [49][50][51] Specic issues pertinent to ultrathin lms and monolayers are also addressed in ref. 52.…”

Section: Methodsmentioning

confidence: 99%

Photochromic and photomechanical responses of an amorphous diarylethene-based polymer: a spectroscopic ellipsometry investigation of ultrathin films

et al. 2014

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This work deals with very thin (14-40 nm) films of a polyester containing diarylethene units in the main chain spin cast on a silicon wafer. By irradiation with UV light the colourless form turns blue due to the appearance of a strong absorption band centred at about 600 nm. The coloured state is thermally stable and the backward conversion can be triggered with visible light. Comparison of broadband (245-1700 nm) spectroscopic ellipsometry data with simulations based on an isotropic, Kramers???Kronig consistent, multiple-resonance model allowed us to determine the complex index of refraction n of the film in its blue and colourless forms. The refractive index of the blue phase neatly exceeds that of the transparent form for wavelengths in the NIR. In particular, out of resonance, at lambda 1700 nm, DeltaRe(n) 0.05. Parallel to the DeltaRe(n) increase, the analysis of ellipsometry data suggests a decrease of the film thickness (about 1.5%) during the transition from the open (transparent) to the closed (coloured) form

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Section: Methodsmentioning

confidence: 99%

Photochromic and photomechanical responses of an amorphous diarylethene-based polymer: a spectroscopic ellipsometry investigation of ultrathin films

et al. 2014

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“…When looking at the ellipsometric evaluation of such ultrathin overlayers, a first order approximation for the Fresnel coefficients can be used, if the substrate can be treated as a half infinite media, and the layer thickness is below 1 nm [57,68]. Then the ellipsometric equation can be simplified to yield a quadratic form.…”

Section: Ultra-thin Filmsmentioning

confidence: 99%

“…In this case it is difficult to separate the refractive index of the film and the film thickness. Consequently only the product of these parameters can be uniquely determined [57,58]. A graphical representation of this experimental limit is presented in Fig.…”

Section: Ultra-thin Filmsmentioning

confidence: 99%

“…The detailed understanding of nano-scale materials is a key prerequisite for future devices, in the context of the scaling down trend toward the molecular level. In spite of the very high sensitivity of the ellipsometric technique, interpreting the ellipsometry spectra for very low coverages (below few nanometers) down to a monolayer or even submonolayer regime remains a challenging task as the optical path of the light through the material is much smaller than the wavelength [57][58][59]. In this case it is difficult to separate the refractive index of the film and the film thickness.…”

Section: Ultra-thin Filmsmentioning

confidence: 99%

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Small Organic Molecules

Gordan

Zahn

2014

Ellipsometry of Functional Organic Surfaces and Films

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In order to improve devices based on organic thin films like organic light emitting diodes (OLEDs) and organic photo voltaic (OPV) cells, the molecular orientation has to be determined and optimized to increase the carrier mobility and the light emission and absorption within the layers. As many of the organic molecules possess an intrinsic molecular anisotropy, molecular ordering will induce optical and electrical anisotropy in the films.The optical anisotropy can be used to determine the average molecular orientation by modeling the anisotropic dielectric function using ellipsometric measurements. An overview of the procedure, valid for planar molecules, will be given in the first part of this chapter, with the main focus on the Phthalocyanine molecular class. The second part of the chapter focuses on vacuum ultra violet (VUV) ellipsometric measurements and the sensitivity gain at ultra-low coverages. Here the discussion will be restricted to optically isotropic films. IntroductionOrganic molecules, which in solid form exhibit semiconducting properties, were long hailed as candidates for cheap, roll to roll electronics. As of today, organic electronics is not anymore a faraway promise, as the huge success and growth of the smartphones market is powered by innovations like organic light emitting diodes (OLEDs). The recent launch of OLED TVs indicates that the OLED technology already reached a maturation state which ensures the long life time needed in television displays. Even in organic photo voltaic (OPV) applications, higher efficiencies than the limit predicted by the exciton dissociation energy were reached. Plastic electronics using organic field effect transistors (OFETs) is another field where huge progress was made in the past decade, and probably soon we will see commercial organic based radio frequency identification tags (ORFIDs). Compared to OPVs, OFETs, and especially to the already commercial OLEDs, molecular spintronics

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“…The calculated data are compared with the ε spectrum of a polycrystalline Cu 2 ZnGeSe 4 thin film determined by spectroscopic ellipsometry (SE) over the photon-energy range of 0.7 to 9.0 eV. SE is known to be a highly suitable method of determining ε and N spectra of semiconductors [22], and therefore, it has been used to characterize the optical properties of many solar cell absorber materials including CdTe [23,24], CuInGaSe 2 [25,26,27], Cu 2 ZnSnS 4 [28,29], and Cu 2 ZnSnSe 4 [5,30,31,32]. For Cu 2 ZnGeSe 4 , León et al [33] reported roomtemperature optical function spectra of bulk crystals.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure and Optical Properties ofCu2ZnGeSe4: First-Principles Calculations and Vacuum-Ultraviolet Spectroscopic Ellipsometric Studies

et al. 2015

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Cu 2 ZnGeSe 4 is of interest for the development of next-generation thin-film photovoltaic technologies. To understand its electronic structure and related fundamental optical properties, we performed first-principles calculations for three structural variations: kesterite, stannite, and primitive-mixed CuAu phases. The calculated data are compared with the room-temperature dielectric function ε = ε 1 + iε 2 spectrum of polycrystalline Cu 2 ZnGeSe 4 determined by vacuumultraviolet spectroscopic ellipsometry in the photon-energy range of 0.7 to 9.0 eV. Ellipsometric data are modeled with the sum of eight Tauc-Lorentz oscillators, and the best-fit model yields the bandgap and Tauc-gap energies of 1.25 and 1.19 eV, respectively. A comparison of overall peak shapes and relative intensities between experimental spectra and the calculated ε data for three structural variations suggests that the sample may not have a pure (ordered) kesterite phase. The complex refractive index N = n + ik, normal-incidence reflectivity R, and absorption coefficients α are calculated from the modeled ε spectrum, which are also compared with those of Cu 2 ZnSnSe 4. The spectral features for Cu 2 ZnGeSe 4 appear to be weaker and broader than those for Cu 2 ZnSnSe 4 , which is possibly due to more structural imperfections presented in Cu 2 ZnGeSe 4 than Cu 2 ZnSnSe 4 .

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Spectroscopic ellipsometry—A perspective

Cited by 33 publications

References 56 publications

Photochromic and photomechanical responses of an amorphous diarylethene-based polymer: a spectroscopic ellipsometry investigation of ultrathin films

Photochromic and photomechanical responses of an amorphous diarylethene-based polymer: a spectroscopic ellipsometry investigation of ultrathin films

Small Organic Molecules

Electronic Structure and Optical Properties ofCu2ZnGeSe4: First-Principles Calculations and Vacuum-Ultraviolet Spectroscopic Ellipsometric Studies

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