Composition of photochromic oxygen-containing yttrium hydride films

Physica Status Solidi (a)

2018

Oxygen‐containing yttrium hydride, YHx:Oy, is an inorganic phothochromic material which exhibits promising features for its application in smart windows, ophthalmic lenses, and many more. In the present work the optical properties of photochromic and non‐photochromic YHx:Oy thin films prepared by magnetron sputtering are studied by variable angle ellipsometry and spectrophotometry. These include the study of the complex refractive index, the transmittance, and luminous transmittance, as well as the reflectance of a selection of samples of diverse structural properties obtained under different deposition conditions. In the case of the photochromic YHx:Oy thin films, the refractive index in the near infrared and visible regions is found similar to the one corresponding to yttrium oxide, Y2O3. However, the YHx:Oy films exhibit a smaller band gap and hence higher absorption in the near ultraviolet than Y2O3. The photodarkening potential of the films are also quantified and characterized by the study and modeling of their optical properties before and after illumination. Our results show that photochromic YHx:Oy films, with a luminous transmittance above 80 % in the clear state, can reduce its transparency up to a 30% after 1 h illumination at 1 Sun.

Section: Resultsmentioning

confidence: 99%

Spectroscopic Ellipsometry and Microstructure Characterization of Photochromic Oxygen‐Containing Yttrium Hydride Thin Films

Montero

Physica Status Solidi (a)

2018

“…YHO films contain two types of competing anions, oxygen and hydrogen, both connected to yttrium atoms . By performing the deposition at different H 2 /Ar flow rates and then oxidizing the films, it is possible to obtain YHO thin films with different concentrations of anion vacancies as well as of hydrogen and oxygen anions with [H] and [O] concentrations anti‐correlated with each other. As it was shown in You et al by the study of transmission spectra, the band gap of the YOH films can be controlled by H 2 /Ar flow rates.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, photo‐induced switching of optical properties has been observed in yttrium hydride (YH x ) films illuminated by visible laser light at pressures of several GPa at room temperature . Such effect was observed by Mongstad et al in oxidized YH x ; since then, YHO has attracted more and more research interest due to its high transparency in the clear state and its ability to photodarken evenly across the visible spectrum. YHO has promising applications in many fields such as ophthalmology, building and transportation industry, etc.…”

Section: Introductionmentioning

confidence: 98%

“…Furthermore, H and O concentrations in the films are somehow connected to each other. Compositional analysis showed that the concentration of the O and H atoms in the films are anti‐correlated. As both H 2 O and O 2 molecules are in the air, the H‐terminated YH 2±δ can react with both.…”

Section: Introductionmentioning

confidence: 99%

“…To date, many interesting properties and phenomena have been reported in YHO resulted by oxidation of the films: photochromic effect, optical bandgap engineering, the enhancement of oxygen concentration in the films with the increase of the hydrogen deposition pressure, etc. Mechanism of the photochromic effect in YHO has been suggested to be caused by formation, after intense illumination with blue/UV light, of small metallic domains within the YHO lattice .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Photoluminescence Properties of Photochromic Yttrium Hydride Films Containing Oxygen

Montero

Galeckas

Physica Status Solidi (b)

2018

Oxidation of YH xAEδ modulates its optical properties by converting it from optically opaque to transparent state to the visible light and electrical properties from metallic conductivity to insulating. The qualitative change of the materials properties are related to oxidation-induced modulation of electronic properties of the material that will influence the band gap and luminescence properties of the oxygen-containing yttrium hydride (YHO). This work presents the optical properties, studied by optical spectrophotometry and photoluminescence spectroscopy, of YHO thin films deposited by reactive magnetron sputtering at different H 2 /Ar flow ratios between 0.18 and 0.28. The indirect and direct band gap of the YHO photochromic films in their clear state is estimated from optical absorption measurements performed at room temperature, and found in the range between 2.5 and 2.6 eV (indirect allowed transition) and between 3.0 and 3.3 eV (direct allowed transition). The study of photoluminescence (PL) properties is performed in the temperature range between 10 and 300 K. The luminescence yield corresponding to the clear state was found to be extremely low in all the YHO films, and it reduced even further once the films darkened under UV-light exposure. The PL emission at room temperature covers the entire UV and visible range, comprising two broad bands centered at around 2.2 and 3.1 eV. The latter band became fine-structured at low-temperatures (10 K), showing a series of distinct PL peaks at energy positions between 2.8 and 3.4 eV which were independent of the H 2 /Ar flow ratio used during deposition. By the comparison of the PL measurements conducted in vacuum with the ones performed in air, it is possible to conclude that the environment plays an important role in the photochromic properties of YHO. The possible intrinsic and extrinsic origin of the structured PL emission is discussed in terms of excitonic features and/or luminescent surface defects. We report that the main optical transitions of the films deposited at different H pressures did not change by variation of temperature or by UV light-induced color change.

Theoretical Design of Effective Multilayer Optical Coatings Using Oxyhydride Thin Films

Strugovshchikov

Pishtshev

Physica Status Solidi (b)

2021

Rare‐earth metal oxyhydride compositions are currently attracting increasing attention to develop materials with unusual optical responses. Herein, using computer simulations of the electronic and optical properties, the optical responses of two stable yttrium oxyhydride compounds, normalY4normalH10O and YHO, are studied for the visible light range. The emphasis is on modeling macroscopic optical characteristics, which are numerically derived within a conventional scheme using refractive indices, and absorption, transmittance, and reflection spectra. The main goal is twofold: first, to simulate spectral behavior of different single‐phase and two‐phase oxyhydride compositions and second, to conduct a comparative analysis that could explain the features of the transmission spectra measured for different samples. Based on the obtained results, models of new optical coatings are proposed in which yttrium oxyhydrides play the key role. In the context of nonlinear optics, the frequency profile of the second‐order susceptibility χ(2)(2ω) for the noncentrosymmetric cubic structure of normalY4normalH10O is evaluated and it is shown that this system could exhibit large optical nonlinearity.