Structures, Phase Equilibria, and Properties of HfO2

Johnson, Brienne; Jones, Jacob L.

doi:10.1016/b978-0-08-102430-0.00002-4

Cited by 20 publications

(18 citation statements)

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“…The XRD patterns show that the films prepared at a T S of between 300 and 675 °C exhibit characteristic nanocrystalline structures of the HfO 2 monoclinic phase (see Scheme ). ,,, The HfO 2 films grown on the heated substrates between 300 and 675 °C show the peaks at 2θ = 28.0, 33.4, and 64.4°, consistent with the ( 1 11), (002), and (023) peaks of monoclinic HfO 2 (ICDD PDF: 04-004-9021), respectively . These peaks are marked with a diamond, ⧫, in Figure .…”

Section: Resultsmentioning

confidence: 53%

“…To mitigate such structural features, increased substrate deposition temperature is often employed to improve thin-film spatial uniformity. With respect to HfO 2 , process-dependent differences in the thermal activation energy can result in different phase configurations (e.g., monoclinic, tetragonal, and/or orthorhombic), , which have been shown to affect the resulting band gap and optical response. More controlled methods, such as sputtering and ALD, are typically preferred to obtain a fully stoichiometric HfO 2 film; however, the associated deposition rates can be slow.…”

Section: Introductionmentioning

confidence: 99%

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Nanoscale-Thick Thin Films of High-Density HfO₂ for Bulk-like Optical Responses

Sun

Jones

Grant

et al. 2021

ACS Appl. Nano Mater.

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The high refractive index, broadband transparency, and low spectral absorption of HfO 2 (hafnia) make it a suitable choice for thermally stable nanoscale optical filters, UV mirrors, and antireflection coatings. However, achieving dense thin films of HfO 2 with bulk-like optical properties has been a challenge due to differences in film stoichiometric and spatial uniformity at nanoscale thicknesses. Here, we assess HfO 2 thin films (i.e., <200 nm thicknesses) prepared using pulsed laser deposition (PLD) at different substrate temperatures (20−675 °C) and the associated chemical, structural, and optical properties are reported. X-ray diffraction analysis reveals that nanoscale-thick thin films of HfO 2 deposited at an ambient substrate temperature (20 °C) using PLD are amorphous with embedded nanocrystallites, whereas films deposited on heated substrates are polycrystalline monoclinic HfO 2 . For the films deposited on heated substrates, further analysis shows that the nanocrystalline phase does not change with increasing substrate temperatures; however, the texture of the crystalline orientation changes to favor (111) at 300−675 °C from the initial (002) orientation at ambient substrate temperature. Such differences in nanoscale-thick thin-film HfO 2 PLD process-dependent amorphousness, crystallinity, and surface textures discussed here exhibit minimal influence on the resulting broadband optical properties (250 nm−30 μm). Furthermore, we show that the complex refractive index of high-density nanoscale-thick thin-film HfO 2 prepared at an ambient substrate temperature using PLD resembles that of bulk HfO 2 responses. The achievement of fully stoichiometric, high-density, thin-film HfO 2 from PLD is expected to further enable thermally robust nanoscale photonic device integration involving low-dimensional high-performance optical and optoelectronic applications.

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Section: Resultsmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Nanoscale-Thick Thin Films of High-Density HfO₂ for Bulk-like Optical Responses

Sun

Jones

Grant

et al. 2021

ACS Appl. Nano Mater.

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“…At high pressure and high temperature conditions, the cubic and the tetragonal phase can be stabilized. 28 It has been shown that, in the presence of particular conditions, the orthorhombic and the rhombohedral phases can also be stabilized. 28 These two phases are non-centrosymmetric and polar where the oxygen atoms in the unit cell determine the stable dipole moment.…”

Section: The Role Of Oxygen Defects In Hfo 2 Phase Stabilizationmentioning

confidence: 99%

“…28 It has been shown that, in the presence of particular conditions, the orthorhombic and the rhombohedral phases can also be stabilized. 28 These two phases are non-centrosymmetric and polar where the oxygen atoms in the unit cell determine the stable dipole moment. It is therefore clear that oxygen is directly related to the ferroelectric response in fluorite-type ferroelectrics.…”

Section: The Role Of Oxygen Defects In Hfo 2 Phase Stabilizationmentioning

confidence: 99%

Interplay between oxygen defects and dopants: effect on structure and performance of HfO₂-based ferroelectrics

Materano

Lomenzo

Kersch

et al. 2021

Inorg. Chem. Front.

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“…Hafnium oxide is considered to be a structural analog of zirconium dioxide, which makes it possible to use it as an alloying element in zirconium ceramics in order to modify its properties. In the study [16], it is shown that yttrium oxide acts as stabilizer of high-temperature phases of hafnium and zirconium oxides. Due to the different valences of Hf4 + and Y3 +, an oxygen vacancy is created which stabilize the high-temperature hafnium phases.…”

Section: Structural Compatibility Of Hfo 2 and Y 2 O 3 Oxidesmentioning

confidence: 99%