Permittivity of Ge, Te and Se thin films in the 200–1500 nm spectral range. Predicting the segregation effects in silver

Ciesielski, Arkadiusz; Skowroński, Łukasz; Pacuski, W.; Szoplik, Tomasz

doi:10.1016/j.mssp.2018.03.003

Cited by 60 publications

(35 citation statements)

References 39 publications

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“…The germanium nanoparticle depositions on ITO resulted in three types of samples: thin (358 nm), medium (965 nm), and thick (8.9 μm) layers. The actual thickness was estimated by the optical absorption at 500 nm using the Lambert–Beer law and the optical absorption coefficient of a 20 nm thick germanium film . Measuring the thickness by AFM is unfortunately not possible because the films are too thick (many monolayers) and the substrate is not exposed.…”

Section: Resultsmentioning

confidence: 97%

Germanium Quantum Dot Grätzel‐Type Solar Cell

Cardoso

Marom

Mayer

et al. 2018

Physica Status Solidi (a)

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Solar cells fabricated from sustainable quantum dot materials are currently not commercially available, but ongoing research provides a steady increase in efficiency and stability of laboratory devices. In this work, the first germanium quantum dot solar cell made with a gas aggregation nanoparticle source is presented. UV–vis spectroscopy reveals quantum confinement, and the spectral response of the germanium quantum dot Grätzel‐type solar cell confirms the presence of large and small band gap optical absorption due to a mix of particle sizes. Some of the particles are small enough to have substantial quantum confinement while others are so large that they have bulk‐like properties. The efficiency of the germanium quantum dot solar cells is very low but could reach 1% if the formation of germanium oxide layers is avoided in future experiments. This first quantum dot solar cell made with a gas aggregation nanoparticle source demonstrates, as a proof of concept, the technological potential for research and applications combining the fields of photovoltaics and gas aggregation nanoparticle sources.

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Section: Resultsmentioning

confidence: 97%

Germanium Quantum Dot Grätzel‐Type Solar Cell

Cardoso

Marom

Mayer

et al. 2018

Physica Status Solidi (a)

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“…In the case of the silver sample deposited with the Se interlayer, the segregation-induced band is barely noticeable. That is most likely due to the fact that a thin Se film has a glass- or even air-like permittivity and this is in agreement with an effective medium approximation [36]. The peak at 326 nm in the electron energy loss function essentially detects the plasma frequency of the sample.…”

Section: Resultsmentioning

confidence: 65%

Interaction of Te and Se interlayers with Ag or Au nanofilms in sandwich structures

Ciesielski

Skowroński

Trzciński

et al. 2019

Beilstein J. Nanotechnol.

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Noble metal nanolayers on flat substrates are often deposited with the use of semiconductor interlayers, which may strongly interact with the noble metal overlayer. We investigated the crystallinity, atomic concentration profile and optical parameters of ≈35 nm-thick silver and gold layers deposited on glass substrates with 2 nm-thick tellurium or selenium interlayers. Our study, based on X-ray reflectometry (XRR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and ellipsometric measurements, showed that using either of these interlayers introduces strain in nanocrystals of both plasmonic films. This, in turn, influences the migration of Se and Te into the metal layers. Selenium atoms migrate both in the silver and gold nanolayers, while tellurium atoms migrate only in silver. The Te concentration curve clearly suggests that this migration is an effect of the segregation of Te atoms in the silver structure. The differences in crystallinity, as well as the migration process, strongly influence the optical parameters of Ag and Au. In the permittivity of Ag deposited on either Te or Se, additional plasmonic bands originating from grain boundary segregation or diffusion occur, while for the Au layer, such resonances were not pronounced. In the permittivity of both materials, the intensity of the interband transition peaks is strongly altered, possibly due to the nano-alloy formation, but more likely due to the microstrain on metal grains.

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“…The XPS spectra were collected 30 days after the fabrication of the samples, to allow germanium to fully segregate towards the surface [37]. For comparison, the spectra for sandwich-like structures where the germanium is deposited between two layers of the same metal, measured 10 days after sample fabrication, from works [38,39], are also presented. A germanium 2p doublet is clearly visible for all the samples on the slope of the inelastic background-above 1200 eV-proving the segregation of this element towards the surface.…”

Section: Methodsmentioning

confidence: 99%

“…Physical phenomena at the interfaces of sandwich−like structures composed of an insulating substrate, elemental semiconductor and noble metal have been experimentally studied and considered in thermodynamic models for a few decades [28][29][30][31][32][33][34][35][36][37][38][39][40][41]. Surface segregation and grain boundary segregation of foreign atoms in a solid solvent considerably influence its dielectric functions and are of great importance in metallurgy and materials science in general [42][43][44].…”

Section: Introductionmentioning

confidence: 99%

“…(a) X-ray photoelectron spectroscopy (XPS) spectra of sandwich-like structures where 2-nm-thick germanium film is deposited in between 20-nm-thick Ag and Au layers, when the Au is at the bottom (orange curve) or at the top (blue curve). For comparison, spectra for structures where the germanium is deposited between two layers of the same metal, from refs[38,39], are also presented. (b) XPS spectra of similar structures, but with an additional Ge film at the substrate/metal interface.…”

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confidence: 99%

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Inhibiting the Segregation of Germanium in Silver Nanolayers

2020

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It is generally acknowledged that using germanium as a wetting film for silver nanolayers decreases the surface roughness of the metal. However, germanium atoms also tend to segregate towards the surface of silver films, increasing ohmic losses in the structure. Here we propose an Au/Ge/Ag based structure where the segregation of germanium in silver is inhibited. X-ray photoelectron spectroscopy (XPS) results show that for the Au/Ge/Ag system, the surface concentration of germanium drops by an order of magnitude relative to multilayers containing only one type of metal (Ag or Au). We have also observed that the time-dependent decrease in the reflectivity due to localized surface plasmon excitation is less prominent in the case of the Au/Ge/Ag structure than in the case of Ag/Ge/Ag. We provide XPS as well as optical reflectometry results to support that claim.

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Permittivity of Ge, Te and Se thin films in the 200–1500 nm spectral range. Predicting the segregation effects in silver

Cited by 60 publications

References 39 publications

Germanium Quantum Dot Grätzel‐Type Solar Cell

Germanium Quantum Dot Grätzel‐Type Solar Cell

Interaction of Te and Se interlayers with Ag or Au nanofilms in sandwich structures

Inhibiting the Segregation of Germanium in Silver Nanolayers

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Permittivity of Ge, Te and Se thin films in the 200–1500 nm spectral range. Predicting the segregation effects in silver

Cited by 60 publications

References 39 publications

Germanium Quantum Dot Grätzel‐Type Solar Cell

Germanium Quantum Dot Grätzel‐Type Solar Cell

Interaction of Te and Se interlayers with Ag or Au nanofilms in sandwich structures

Inhibiting the Segregation of Germanium in Silver Nanolayers

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Product

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Permittivity of Ge, Te and Se thin films in the 200–1500 nm spectral range. Predicting the segregation effects in silver