Formation of the Intrinsic Absorption Edge in Nanostructured Hafnium Dioxide Powder

Shilov, A. O.; Вохминцев, А. С.; Henaish, A. M. A.; Weinstein, I. A.

doi:10.3103/s1062873822070279

Cited by 1 publication

(4 citation statements)

References 20 publications

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“…The authors claim that the indirect bandgap in amorphous as-grown films is 5.60 eV, which decreases as the annealing temperature grows, reaching 5.13 eV for thin films annealed at 600 • C with a monoclinic crystal structure. Nevertheless, the values obtained are reconciled with previous estimates of direct E g for amorphous and monoclinic hafnia in various structural modifications, such as nanopowder (in range of 5.5-5.8 eV) [7,25,39,40], thin films (5.3-5.8 eV) [41][42][43], bulk single crystal (5.89 eV) [44], etc.…”

Section: Estimation Of the Bandgap Widthsupporting

confidence: 84%

“…In hafnia, we have previously detected an intrinsic absorption edge formed via direct and indirect allowed band-to-band transitions [7,25]. However, due to the distortion of the intrinsic absorption edge in the low-energy region, we did not succeed in determining indirect optical gap width for as-grown and annealed NTs.…”

Section: Spectral Characteristics Of Luminescencementioning

confidence: 73%

“…The resulting absorption spectrum F R (hν) (see Figure 3b) includes a broad Gaussian-shaped shoulder that emerged because of oxygen vacancies: their absorption lies within energy region of hν > 3 eV [36]. In hafnia, we have previously detected an intrinsic absorption edge formed via direct and indirect allowed band-to-band transitions [7,25]. However, due to the distortion of the intrinsic absorption edge in the low-energy region, we did not succeed in determining indirect optical gap width for as-grown and annealed NTs.…”

Section: Estimation Of the Bandgap Widthmentioning

confidence: 93%

“…Conducting experimental research on the optical and luminescent properties of HfO 2 NTs is extremely important for establishing the aspects of their energy spectrum caused by the morphology of the material. Currently, independent investigations of the optical and luminescent properties of bulk and thin-film hafnia samples doped with various ions, mainly with an amorphous and monoclinic structure, have been undertaken [8,19,[21][22][23][24][25]. Simultaneously, examining the developed surface structures of hafnia could provide insight into the role of surface optically active centers and defects of various natures in the radiative and non-radiative relaxation processes of electronic excitations in HfO 2 nanotubes.…”

Section: Introductionmentioning

confidence: 99%

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Luminescence in Anion-Deficient Hafnia Nanotubes

Shilov,

Kamalov,

Karabanalov

et al. 2023

Nanomaterials

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Hafnia-based nanostructures and other high-k dielectrics are promising wide-gap materials for developing new opto- and nanoelectronic devices. They possess a unique combination of physical and chemical properties, such as insensitivity to electrical and optical degradation, radiation damage stability, a high specific surface area, and an increased concentration of the appropriate active electron-hole centers. The present paper aims to investigate the structural, optical, and luminescent properties of anodized non-stoichiometric HfO2 nanotubes. As-grown amorphous hafnia nanotubes and nanotubes annealed at 700 °C with a monoclinic crystal lattice served as samples. It has been shown that the bandgap Eg for direct allowed transitions amounts to 5.65 ± 0.05 eV for amorphous and 5.51 ± 0.05 eV for monoclinic nanotubes. For the first time, we have studied the features of intrinsic cathodoluminescence and photoluminescence in the obtained nanotubular HfO2 structures with an atomic deficiency in the anion sublattice at temperatures of 10 and 300 K. A broad emission band with a maximum of 2.3–2.4 eV has been revealed. We have also conducted an analysis of the kinetic dependencies of the observed photoluminescence for synthesized HfO2 samples in the millisecond range at room temperature. It showed that there are several types of optically active capture and emission centers based on vacancy states in the O3f and O4f positions with different coordination numbers and a varied number of localized charge carriers (V0, V−, and V2−). The uncovered regularities can be used to optimize the functional characteristics of developed-surface luminescent media based on nanotubular and nanoporous modifications of hafnia.

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