Refraction and Dispersion of Synthetic Sapphire

Malitson, Irving H.

doi:10.1364/josa.52.001377

Cited by 393 publications

(143 citation statements)

References 5 publications

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“…The ordinary dielectric function was obtained by fitting and data from all angles of incidence together in a multilayer model [56], which also accounts for the surface roughness via the Bruggeman effective medium approximation [57] and for the (0001)-oriented α-Al 2 O 3 substrate. The dielectric functions published by Malitson and Tomiki et al [58,59] for the visible-ultraviolet spectral range were used to describe the sapphire substrate. In the infrared spectral range, we determined experimentally the dielectric response of sapphire on polished sapphire substrates with different surface orientations, i.e., (0001), (1100), and (1120) orientations.…”

Section: Methodsmentioning

confidence: 99%

Ordinary dielectric function of corundumlike α−Ga2O3 from 40 meV to 20 eV

Feneberg

Nixdorf

Neumann

et al. 2018

Phys. Rev. Materials

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The linear optical response of metastable α-Ga 2 O 3 is investigated by spectroscopic ellipsometry. We determine the ordinary dielectric function from lattice vibrations up to the vacuum ultraviolet spectral range at room temperature for a sample with a (0001) surface. Three out of four E u infrared-active phonon modes are unambiguously determined, and their frequencies are in good agreement with density functional theory calculations. The dispersion of the refractive index in the visible and ultraviolet part of the spectrum is determined. High-energy interband transitions are characterized up to 20 eV. By comparison with the optical response of α-Al 2 O 3 and with theoretical results, a tentative assignment of interband transitions is proposed.

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Section: Methodsmentioning

confidence: 99%

Ordinary dielectric function of corundumlike α−Ga2O3 from 40 meV to 20 eV

Feneberg

Nixdorf

Neumann

et al. 2018

Phys. Rev. Materials

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“…Regarding (i) and (iii), in view of the cross sections observed in the SEM, considering an equal contribution to the refractive index of the transition middle layer from the materials at both sides of the interface seems reasonable. In the case of the mesostructured Al 2 O 3 scaffold, a 54% porosity prior to perovskite infiltration was attained from the fitting of its experimental reflectance, assuming that the thickness and the permittivity of the alumina are known from the analysis of SEM images and the scientific literature, 31 respectively. The very similar results attained from the different effective medium equations employed led us to consider the simplest approximation, that is, the volumeweighted average, to calculate the effective optical constants.…”

mentioning

confidence: 99%

Optical Description of Mesostructured Organic–Inorganic Halide Perovskite Solar Cells

Anaya

Lozano

Calvo

et al. 2014

J. Phys. Chem. Lett.

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Herein we describe both theoretically and experimentally the optical response of solution-processed organic−inorganic halide perovskite solar cells based on mesostructured scaffolds. We develop a rigorous theoretical model using a method based on the propagation of waves in layered media, which allows visualizing the way in which light is spatially distributed across the device and serves to quantify the fraction of light absorbed by each medium comprising the cell. The discrimination between productive and parasitic absorption yields an accurate determination of the internal quantum efficiency. State-of-the-art devices integrating mesoporous scaffolds infiltrated with perovskite are manufactured and characterized to support the calculations. This combined experimental and theoretical analysis provides a rational understanding of the optical behavior of perovskite cells and can be beneficial for the judicious design of devices with improved performance. Notably, our model justifies the presence of a solid perovskite capping layer in all of the highest efficiency perovskite solar cells based on thinner mesoporous scaffolds.O rganic−inorganic halide perovskite solar cells have driven a paradigm shift in photovoltaics (PV) since they are breaking with the sempiternal trade-off between power conversion efficiency and fabrication cost. 1−5 Not long after their inception, this solar cell concept is already striding ahead in the emerging PV efficiency race, having reached in the last 2 years certified efficiency values that significantly surpass all of the ones attained for other cells based on solution-processed materials and rapidly approaching existing commercial thin-film technologies. 6 This rapid progress has been based on improvements of fabrication methods, charge carrier materials, device architecture, morphology and crystallinity of the perovskite thin films, and the composition of the perovskite. 7−19 Another route to boost the efficiency of solar cell devices consists of the optimization of their optical design to maximize light harvesting and charge collection. 20 In this regard, efforts have been made to optimize the electro-optical performance of both materials 21−24 and devices. 25 In this respect, only cells that make use of flat, evaporated, perovskite layers have been modeled and, to the best of our knowledge, a detailed description of the optical behavior of the complete mesostructured device is still missing, especially understanding the difference between the optical properties of the perovskite when forming a solid crystalline film, in comparison with when infiltrated into a mesoporous scaffold.Herein we perform an in-depth experimental and theoretical analysis of the optical effects occurring in state-of-the-art solution-processed organic lead halide perovskite cells. We develop a rigorous theoretical model based on the transfer matrix formalism, 26 which allows us to calculate the electric field intensity within the layered structure and thus to visualize the effect of each component ...

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“…These results demonstrate that the crystallinity of crystals grown with the TSMG method had similar quality to those grown with the KY method, which is sufficient for LED substrates. Figure 3 shows the transmittance of the as-grown crystals grown by different methods, where the dotted curve shows the ideal transmittance calculated from the refractive index using the Sellmeier dispersion formula 21) for a perfect sapphire crystal without absorption. The TSMG sapphire had significant absorp- The F-center formation is described as follows:…”

Section: Methodsmentioning

confidence: 99%

Crystal growth of large sapphire and its optical properties

Kawaminami

Mochizuki²,

Adachi

et al. 2014

J. Ceram. Soc. Japan

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Large sapphire crystals for 200-mm LED wafers were successfully grown by the top seeded melt growth (TSMG) method. The sapphire had excellent crystallinity as LED substrates. However, in the as-grown crystal, there was remarkable absorption in UV region caused by the F-center (V Â O ). To reduce the absorption, we studied several heat treatment methods using oxidized atmospheres. In air or O 2 atmospheres, the absorption was difficult to reduce because oxygen diffusion was slow and new absorption occurred. We found that heat treatment in an H 2 O 2 combustion flame was highly effective in reducing the absorption in the UV region. After the combustion flame heat treatment, the sample had an absorption coefficient less than 0.5 cm 1 at 200 nm, and no photoluminescent emissions were caused by color centers. Consequently, sapphire crystals grown by the TSMG method had good crystallinity and low absorption in the UV region.

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Refraction and Dispersion of Synthetic Sapphire

Cited by 393 publications

References 5 publications

Ordinary dielectric function of corundumlike α−Ga2O3 from 40 meV to 20 eV

Ordinary dielectric function of corundumlike α−Ga2O3 from 40 meV to 20 eV

Optical Description of Mesostructured Organic–Inorganic Halide Perovskite Solar Cells

Crystal growth of large sapphire and its optical properties

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