Electronic structure and vacancy formation in photochromic yttrium oxy-hydride thin films studied by positron annihilation

Plokker, M.P.; Eijt, S.W.H.; Naziris, Frideriki; Schüt, H.; Nafezarefi, F.; Schreuders, Herman; Cornelius, S.; Dam, B.

doi:10.1016/j.solmat.2017.03.011

Cited by 17 publications

(23 citation statements)

References 38 publications

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“…A recent extensive study by Cornelius et al [7] reports on the detailed structural and compositional evolution of Y/YH x /YO x H 3−2x /Y 2 O 3 films upon varying the oxygen-to-hydrogen ratio in the Y-H-O ternary phase diagram [7]. Our previous study showed that the trends in the positron Doppler S-and W -parameter of Y/YH x /YO x H 3−2x /Y 2 O 3 thin films strongly correlate with the variation in their electronic structure, ranging from metallic and semiconducting nature to a widebandgap insulator with increased O:H ratio [8]. Here, we report PAS measurements during an in situ UV illumination experiment on a photochromic YO x H y thin film.…”

Section: Introductionmentioning

confidence: 95%

Photochromic YO_xH_y Thin Films Examined by <i>in situ</i> Positron Annihilation Spectroscopy

et al. 2020

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Doppler broadening positron annihilation spectroscopy depth profiles were collected on photochromic YOxHy thin films. In situ UV illumination of photochromic semiconductor YOxHy films leads to an increase in S-parameter and a large reduction in W -parameter, possibly caused by a change in the charge state of vacancies or the growth of hydrogen-rich metallic Y(Ox)Hy clusters, albeit that vacancy formation or changes in positronium formation during illumination might also play a role. Intriguingly, both the S-and W -parameters increase during thermal bleaching, indicating that another process takes place. The Doppler parameters do not return to their initial values after complete thermal bleaching, suggesting that persistent local rearrangements of vacancies and possibly hydride ions have occurred during the full photodarkening-thermal bleaching cycle. Positron annihilation lifetime spectroscopy shows that a small fraction of positronium is formed in as-deposited YOxHy films, indicating that the films contain some nanopores.

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Section: Introductionmentioning

confidence: 95%

Photochromic YO_xH_y Thin Films Examined by <i>in situ</i> Positron Annihilation Spectroscopy

et al. 2020

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“…It is then oxidized by exposure to air, resulting in photochromic polycrystalline oxyhydride films [11]. Several studies further attempted at each time to reveal the mechanisms of photochromism in rare-earth metal oxyhydrides through time resolved X-ray diffraction using synchrotron radiation [12], composition analysis [3,9,13] and positron annihilation spectroscopy (PAS) [14,15]. However, the answer for the exact mechanism for rare-earth metal oxyhydrides still debated.…”

Section: Introductionmentioning

confidence: 99%

Preferential Orientation of Photochromic Gadolinium Oxyhydride Films

et al. 2020

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We report preferential orientation control in photochromic gadolinium oxyhydride (GdHO) thin films deposited by a two-step process. Gadolinium hydride (GdH2-x) films were grown by reactive magnetron sputtering, followed by oxidation in air. The preferential orientation, grain size, anion concentrations and photochromic response of the films were strongly dependent on the deposition pressure. The GdHO films showed a preferential orientation along the [100] direction and exhibited photochromism when synthesized at deposition pressures of up to 5.8 Pa. The photochromic contrast was larger than 20% when the films were deposited below 2.8 Pa with a 0.22 H2/Ar flow ratio. We argue that the relation of preferential orientation and the post deposition oxidation since oxygen concentration is known to be a key parameter for photochromism in rare-earth oxyhydride thin films. The experimental observations described above were explained by the decrease of the grain size as a result of the increase of the deposition pressure of the sputtering gas, followed by a higher oxygen incorporation.

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“…Positron annihilation results of YHO suggest that UV light causes either a generation of a small concentration of cation vacancies, or an assembling of vacancies into vacancy clusters. [8] These observed structural changes were irreversible during the bleaching process, and therefore cannot be the reason for the reversible change in color. Nuclear magnetic resonance has indicated that YHO films in an initially transparent state contain three hydrogen species with different mobility, of which the most mobile one stays trapped under illumination and is released thereafter in the relaxation process.…”

Section: Introductionmentioning

confidence: 99%

Yttrium oxyhydrides for photochromic applications: Correlating composition and optical response

Moldarev

Moro

You

et al. 2018

Phys. Rev. Materials

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It has been recently demonstrated that yttrium oxyhydride (YHO) films can exhibit reversible photochromic properties when exposed to illumination at ambient conditions. This switchable optical property enables their utilization in many technological applications, such as smart windows, sensors, goggles, medical devices, etc. However, how the composition of the films affects their optical properties is not fully clear and therefore demands a straightforward investigation. In this work, the composition of YHO films manufactured by reactive magnetron sputtering under different conditions is deduced in a ternary diagram from Timeof-Flight Elastic Recoil Detection Analysis (ToF-ERDA). The results suggest that stable compounds are formed with a specific chemical formula-YH 2-δ O δ. In addition, optical and electrical properties of the films are investigated, and a correlation with their compositions is established. The corresponding photochromic response is found in a specific oxygen concentration range (0.45 < δ < 1.5) with maximum and minimum of magnitude on the lower and higher border, respectively.

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Electronic structure and vacancy formation in photochromic yttrium oxy-hydride thin films studied by positron annihilation

Cited by 17 publications

References 38 publications

Photochromic YO_xH_y Thin Films Examined by <i>in situ</i> Positron Annihilation Spectroscopy

Photochromic YO_xH_y Thin Films Examined by <i>in situ</i> Positron Annihilation Spectroscopy

Preferential Orientation of Photochromic Gadolinium Oxyhydride Films

Yttrium oxyhydrides for photochromic applications: Correlating composition and optical response

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Electronic structure and vacancy formation in photochromic yttrium oxy-hydride thin films studied by positron annihilation

Cited by 17 publications

References 38 publications

Photochromic YOxHy Thin Films Examined by <i>in situ</i> Positron Annihilation Spectroscopy

Photochromic YOxHy Thin Films Examined by <i>in situ</i> Positron Annihilation Spectroscopy

Preferential Orientation of Photochromic Gadolinium Oxyhydride Films

Yttrium oxyhydrides for photochromic applications: Correlating composition and optical response

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Product

Resources

About

Photochromic YO_xH_y Thin Films Examined by <i>in situ</i> Positron Annihilation Spectroscopy

Photochromic YO_xH_y Thin Films Examined by <i>in situ</i> Positron Annihilation Spectroscopy