Validity of Ellipsometry for Determining the Average Thickness of Thin, Discontinuous, Absorbing Films*

Bennett, H. E.; Burge, D. K.; Peck, R. L.; Bennett, Jean M.

doi:10.1364/josa.59.000675

Cited by 22 publications

(4 citation statements)

References 18 publications

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“…In this regard, we coated the nanowires with silver sulfide via SILAR. We chose silver sulfide in view of its advantageous properties of bandgap of ∼1.0 eV, high absorptivity (10 4 cm –1 ), high photostability, , and importantly, the energy level alignments with bismuth sulfide.…”

Section: Resultsmentioning

confidence: 99%

Solution Processed Bismuth Sulfide Nanowire Array Core/Silver Sulfide Shell Solar Cells

et al. 2015

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Low bandgap inorganic semiconductor nanowires have served as building blocks in solution processed solar cells to improve their power conversion capacity and reduce fabrication cost. In this work, we first reported bismuth sulfide nanowire arrays grown from colloidal seeds on a transparent conductive substrate via mild aqueous chemistry and demonstrated a novel core−shell nanowire architecture to enhance the photovoltaic performances of hybrid solar cells. We found that the bismuth sulfide nanowire core/silver sulfide shell structure reduces the interfacial charge recombination between the core and a hole transporter layer and enables efficient charge separation in a type-II core−shell heterojunction. The bismuth sulfide nanowire core/silver sulfide shell combined with 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) reached solar-to-electricity power conversion efficiency of 2.5%, advancing the field of solution processed solar cells based on environmentally friendly metal chalcogenide semiconductors.

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Section: Resultsmentioning

confidence: 99%

Solution Processed Bismuth Sulfide Nanowire Array Core/Silver Sulfide Shell Solar Cells

et al. 2015

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“…Furthermore, if the difference of 7 Å could be attributed to changes in orientation alone, this would imply that the total length of the molecules should be measured regardless of the hydration of the headgroup; that is, the degree of hydration would have no effect on the refractive index of that moiety. The refractive index, which is a macroscopic concept that depends on the ability of individual atoms to polarize in response to an external field, is to our knowledge still valid for submonolayer films . The headgroup region is known to be hydrated with a degree of hydration that varies as a function of the molecular area: more hydrated in the condensed state than in the S state .…”

Section: Resultsmentioning

confidence: 99%

Simultaneous Thickness and Refractive Index Determination of Monolayers Deposited on an Aqueous Subphase by Null Ellipsometry

2001

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For the first time, the thickness and refractive index of monolayers at the air/water interface have simultaneously been determined by null ellipsometry. Separation of refractive index from film thickness has been achieved by highly precise measurements of the two ellipsometric angles Ψ and Δ. In the solid state, film thicknesses of arachidic acid and valine gramicidin A obtained by ellipsometry are comparable with those obtained by the X-ray techniques. For arachidic acid in the condensed state, our results suggest that only the thickness of the hydrophobic moiety is measured. When highly hydrated, the thickness of the polar headgroup is not detected. This is presumably due to its refractive index being the same as that of the bulk water; hence, the calculated film thickness corresponds to the thickness of the hydrophobic part only. As molecular area is reduced, the polar headgroup gradually loses hydration water molecules causing its refractive index profile to become different from that of the bulk water. Our results suggest that the measurable thickness of the film-forming molecules increases as the degree of dehydration of the headgroup increases.

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“…Silver is known to undergo tarnishing in ambient environment, through surface oxide or sulfide formation. 22,23 Thus, a densified dielectric outer layer or another stable surface passivation layer may be required to protect Ag-based multilayer structures. Alternatively, recent results demonstrated that graphene layers can serve as an excellent protection against tarnishing of Ag-based plasmonic structures.…”

Section: Discussionmentioning

confidence: 99%

Permittivity evaluation of multilayered hyperbolic metamaterials: Ellipsometry vs. reflectometry

Tumkur

Barnakov

Kee

et al. 2015

Journal of Applied Physics

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Metal-dielectric nanolaminates represent a class of hyperbolic metamaterials with uniaxial permittivity tensor. In this study, we critically compare permittivity extraction of nanolaminate samples using two techniques: polarized reflectometry vs. spectroscopic anisotropic ellipsometry. Both Au/MgF2 and Ag/MgF2 metal-dielectric stacks are examined. We demonstrate the applicability of the treatment of the multilayered material as a uniaxial medium and compare the derived optical parameters to those expected from the effective medium approximation. We also experimentally compare the effect of varying the material outer layer on the homogenization of the composite. Additionally, we introduce a simple empirical method of extracting the epsilon-near-zero point of the nanolaminates from normal incidence reflectance. The results of this study are useful in accurate determination of the hyperbolic material permittivity and in the ability to tune its optical properties.

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Validity of Ellipsometry for Determining the Average Thickness of Thin, Discontinuous, Absorbing Films*

Cited by 22 publications

References 18 publications

Solution Processed Bismuth Sulfide Nanowire Array Core/Silver Sulfide Shell Solar Cells

Solution Processed Bismuth Sulfide Nanowire Array Core/Silver Sulfide Shell Solar Cells

Simultaneous Thickness and Refractive Index Determination of Monolayers Deposited on an Aqueous Subphase by Null Ellipsometry

Permittivity evaluation of multilayered hyperbolic metamaterials: Ellipsometry vs. reflectometry

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