Amorphous hafnium oxide thin films for antireflection optical coatings

Khoshman, Jebreel M.; Khan, Aurangzeb; Kordesch, Martin E.

doi:10.1016/j.surfcoat.2007.07.095

Cited by 98 publications

(45 citation statements)

References 10 publications

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“…Thin films of amorphous (a) hafnium dioxide a-HfO 2 are used for optical coating [1,2] and as the gate dielectric in complementary metal oxide semiconductor (CMOS) technology due to high dielectric constant and reliability [3,4]. Hafnia layers are also applied in resistive memory devices [5][6][7] and as the gate dielectric for thin film transistors (TFTs) based on metal oxide channel materials, such as indium zinc oxide and indium gallium zinc oxide [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Interactions of hydrogen with amorphous hafnium oxide

2017

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We used density functional theory (DFT) calculations to study the interaction of hydrogen with amorphous hafnia (a-HfO 2 ) using a hybrid exchange-correlation functional. Injection of atomic hydrogen, its diffusion towards electrodes, and ionization can be seen as key processes underlying charge instability of high-permittivity amorphous hafnia layers in many applications. Hydrogen in many wide band gap crystalline oxides exhibits negative-U behavior (+1 and −1 charged states are thermodynamically more stable than the neutral state) . Our results show that in a-HfO 2 hydrogen is also negative-U, with charged states being the most thermodynamically stable at all Fermi level positions. However, metastable atomic hydrogen can share an electron with intrinsic electron trapping precursor sites [Phys. Rev. B 94, 020103 (2016).] forming a [e − tr + O-H] center, which is lower in energy on average by about 0.2 eV. These electron trapping sites can affect both the dynamics and thermodynamics of the interaction of hydrogen with a-HfO 2 and the electrical behavior of amorphous hafnia films in CMOS devices.

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Section: Introductionmentioning

confidence: 99%

Interactions of hydrogen with amorphous hafnium oxide

2017

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“…Hafnium dioxide (hafnia, HfO 2 ) is attracting a lot of attention as a perspective high-k material for electronic [1,2] as well as optical applications such as antireflective coatings [3,4], or heat [5] and laser mirrors [6]. According to the ambient pressure phase diagram, three crystalline polymorphs of HfO 2 are stable ( Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Accurate prediction of band gaps and optical properties of HfO₂

Ondračka

Holec

Nečas

et al. 2016

J. Phys. D: Appl. Phys.

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Abstract. We report on optical properties of various polymorphs of hafnia predicted within the framework of density functional theory. The full potential linearised augmented plane wave method was employed together with the TranBlaha modified Becke-Johnson potential (TB-mBJ) for exchange and local density approximation for correlation. Unit cells of monoclinic, cubic, and tetragonal crystalline, and a simulated annealing-based model of amorphous hafnia were fully relaxed with respect to internal positions and lattice parameters. Electronic structures and band gaps for monoclinic, cubic, tetragonal and amorphous hafnia were calculated using three different TB-mBJ parametrisation and the results were critically compared with available experimental and theoretical reports. Conceptual differences between a straightforward comparison of experimental measurements to a calculated band gap on the one hand and to a whole electronic structure (density of electronic states) on the other hand, were pointed out, suggesting the latter should be used whenever possible. Finally, dielectric functions were calculated at two levels, using the random phase approximation without local field effects and with a more accurate Bethe-Salpether equation (BSE) to account for excitonic effects. We conclude that a satisfactory agreement with experimental data for HfO 2 was obtained only in the latter case.

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“…In particular, hafnium dioxide (HfO 2 ) termed as hafnia and other hafnia-based materials find wide applications in the field of microelectronics as good replacements of silica in field effect transistor gates due to their good balanced combination of properties such as a high dielectric constant, relatively large band gap, large heat of formation, good thermal and chemical stability on Si, large barrier heights at interfaces with Si and adequate compatibility with n + polysilicon gate electrodes [1]. Hafnia is used as a high refractive index material and in the form of thin films as heat resistant and strongly reflective protective optical coating [2].…”

Section: Introductionmentioning

confidence: 99%