Improvement to reflective dielectric film color pictures

Kvavle, Joshua; Bell, Cara; Henrie, Justin; Schultz, Stephen M.; Hawkins, Aaron R.

doi:10.1364/opex.12.005789

Cited by 13 publications

(14 citation statements)

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“…For both types of samples, TaS 2 and Ta 0.9 Mo 0.1 S 2 , few-layer crystals were mechanically exfoliated from single-crystal bulk samples and deposited on SiO 2 /Si substrates (see methods). Inspection of the samples under the optical microscope enables a quick identification of possible few-layered crystals due to differences in interference colors [34,38]. The selected flakes were characterized using both atomic force microscopy (AFM) and Raman spectroscopy.…”

Section: Resultsmentioning

confidence: 99%

Raman spectroscopy of few-layers TaS$_2$ and Mo-doped TaS$_2$ with enhanced superconductivity

Valencia-Ibáñez¹,

Jimenez-Guerrero²,

Salcedo-Pimienta³

et al. 2022

Preprint

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The use of simple, fast and economic experimental tools to characterize low-dimensional materials is an important step in the process of democratizing the use of such materials in laboratories around the world. Raman spectroscopy has arisen as a way of indirectly determining the thickness of nanolayers of transition metal dichalcogenides (TMDs), avoiding the use of more expensive tools such as atomic force microscopy, and it is therefore a widely used technique in the study of semiconducting TMDs. However, the study of many metallic TMDs in the limit of few atomic layers is still behind when compared to their semiconducting counterparts, partly due to the lack of similar alternative characterization studies. In this work we present the characterization of the Raman spectrum, specifically of the E 1 2g -and A1g-modes, of mechanically exfoliated crystals of Ta1−xMoxS2 , a metallic TMD which exhibits charge density wave formation and superconductivity. The clear identification of contributions to the Raman spectrum coming from the SiO2/Si substrate, which overlap with the peaks coming from the sample, and which dominate in intensity in the few-layer-samples limit, allowed the isolation of the individual E 1 2g -and A1g-modes of the samples and, for the first time, the observation of a clear evolution of the Raman shifts of both modes as a function of sample thickness. The evolution of such peaks qualitatively resembles the evolution seen in other TMDs, and provide a way of indirectly determining sample thickness in the limit of few atomic layers at a low cost. In addition, we observe a softening (red-shift) of both E 1 2g -and A1g-modes with Mo-doping in the nanolayers, possibly related to the increased out-of-plane lattice parameter with respect to the pure compound.

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Section: Resultsmentioning

confidence: 99%

Raman spectroscopy of few-layers TaS$_2$ and Mo-doped TaS$_2$ with enhanced superconductivity

Valencia-Ibáñez¹,

Jimenez-Guerrero²,

Salcedo-Pimienta³

et al. 2022

Preprint

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“…The physics behind the optical visibility of these atomically thin crystals can be illustrated with the example of the interference colors in SiO 2 thin films. It is well known that the thickness of thermally grown SiO 2 layers on Si wafers can be readily determined with ≈5 nm accuracy from their color under white‐light illumination 20, 21. This apparent color is due to the interference of the paths reflected at the air/SiO 2 and SiO 2 /Si interfaces (similar to a Fabry–Perot interferometer).…”

Section: Resultsmentioning

confidence: 99%

“…The SiO 2 layer, with a thickness d 2 , is described by its refractive index ñ 2 ( λ ) which also depends on the illumination wavelength 27. Note that, using the refractive indices of SiO 2 and Si, one can accurately account for the interference colors of the oxidized wafers with a Fresnel law‐based model 20, 21. The reflected intensity for a SiO 2 /Si wafer ( I 0 ) can be expressed in terms of the phase shift produced by the SiO 2 layer ( Φ 2 = 2π ñ 2 d 2 / λ ) and the amplitudes of the paths reflected at the air/SiO 2 and SiO 2 /Si interfaces ( r 02 and r 23 respectively), where the amplitude of the reflected path in the interface between the media i and j is r ij = ( ñ i ‐ ñ j )/( ñ i + ñ j ) with ñ j being the refractive index of medium j .…”

Section: Resultsmentioning

confidence: 99%

Atomically Thin Mica Flakes and Their Application as Ultrathin Insulating Substrates for Graphene

Castellanos-Gómez

Wojtaszek

Tombros

et al. 2011

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“…In addition, it is possible to get a rough estimate of the thickness of the flakes due to a light interference effect owing to the presence of the thin silicon oxide layer which makes their color thickness dependent under white light illumination (this effect is usually referred as interference color). [35] Typically, the obtained flakes with The root mean square roughness of the thinnest layer is 0.22 nm 2 , while the roughness of the SiO 2 substrate is 0.20 nm 2 . In some flakes the AFM topography shows a spike at the step edges, which could be attributed to rolling or folding during the deposition of the flake.…”

Section: Tase 2 Single-crystal Fabricationmentioning

confidence: 99%

“…In addition, it is possible to get a rough estimate of the thickness of the flakes due to a light interference effect owing to the presence of the thin silicon oxide layer which makes their color thickness dependent under white light illumination (this effect is usually referred as interference color). [35] Typically, the obtained flakes with (c) AFM topography image of the region marked by a dashed rectangle in (a). A topographic line profile along the horizontal dashed line is inserted to indicate the thickness of the flakes.…”

Section: Tase 2 Single-crystal Fabricationmentioning

confidence: 99%

Fast and reliable identification of atomically thin layers of TaSe2 crystals

et al. 2013

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Deposition of clean and defect-free atomically thin two-dimensional crystalline flakes on surfaces by mechanical exfoliation of layered bulk materials has proven to be a powerful technique, but it requires a fast, reliable and non-destructive way to identify the atomically thin flakes among a crowd of thick flakes. In this work, we provide general guidelines to identify ultrathin flakes of TaSe 2 by means of optical microscopy and Raman spectroscopy. Additionally, we determine the optimal substrates to facilitate the optical identification of atomically thin TaSe 2 crystals. Experimental realization and isolation of ultrathin layers of TaSe 2 enables future studies on the role of the dimensionality in interesting phenomena such as superconductivity and charge density waves. KEYWORDSatomically thin layer, metal dichalcogenide, layered superconductor, TaSe 2 , optical microscopy, Raman spectroscopy This is the post-peer reviewed version of the following article: A.Castellanos-Gomez et al. "Fast and reliable identification of atomically thin layers of TaSe 2 crystals".2 thoroughly characterized, [16][17][18][19][20] most of other possible two-dimensional (2D) crystals with attractive properties remain barely explored. For instance, layered transition metal dichalcogenides with the formula MX 2 (M = Mo, W, Nb, Ta or Ti and X = Se, S or Te) present a broad variety of electrical properties ranging from wide band-gap semiconductors to superconductors. As in the case of graphene, while fabrication by mechanical exfoliation from bulk crystals of these layered materials is rather simple,[2] identification of atomically thin flakes requires fast, reliable and non-destructive characterization techniques. [21][22][23][24][25][26][27] The realization of ultrathin superconducting layers would enable one to employ the electric field effect to control physical properties such as the superconducting transition temperature or to study the interplay between the superconductivity and the sample dimensionality. However, among the family of transition metal dichalcogenides, the studies on atomically thin superconducting layers are scarce and mainly focused on NbSe 2 and TaS 2 crystals. [3, 4,28] TaSe 2 is a good example of a layered material which has not been studied in its This is the post-peer reviewed version of the following article: A.Castellanos-Gomez et al. "Fast and reliable identification of atomically thin layers of TaSe 2 crystals".3 one end of the ampoule and the latter was exhaustively evacuated and flame-sealed. The quartz tube was finally placed inside a three-zone split muffle where a gradient of 25 ºC was established between the leftmost load (725 ºC) and central growth (700 ºC) zones. A gradient of 25 ºC was also set between the rightmost and central regions. The temperature gradient was maintained constant during 15 days and the muffle was eventually switched off and left to cool down at ambient conditions. Millimetric TaSe 2 crystals were recovered from the ampoule's central zone, exhaustively rinsed with diethyl e...

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Improvement to reflective dielectric film color pictures

Cited by 13 publications

References 0 publications

Raman spectroscopy of few-layers TaS$_2$ and Mo-doped TaS$_2$ with enhanced superconductivity

Raman spectroscopy of few-layers TaS$_2$ and Mo-doped TaS$_2$ with enhanced superconductivity

Atomically Thin Mica Flakes and Their Application as Ultrathin Insulating Substrates for Graphene

Fast and reliable identification of atomically thin layers of TaSe2 crystals

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