Dielectric properties and Raman spectra of ZnO from a first principles finite-differences/finite-fields approach

Calzolari, Arrigo; Nardelli, Marco Buongiorno

doi:10.1038/srep02999

Cited by 121 publications

(87 citation statements)

References 38 publications

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“…Figure 4f shows the valence band spectra of pure and doped films. The most intense transitions are attributed to the Zn3d band (Joshi et al 2010;Calzolari and Nardelli 2013). The 3d peak positions are located at 9.88 and 8.99 eV for pure and doped film, respectively.…”

Section: Characterization Techniquesmentioning

confidence: 93%

The influence of Ce doping on the structural and optoelectronic properties of RF-sputtered ZnO films

García-Méndez¹,

Segura

Coello

et al. 2015

Opt Quant Electron

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Using X-ray diffraction, UV-Visible spectroscopy, XPS and photoluminescence (PL) measurements, the structural, optical and electronic properties of ZnO and Cedoped ZnO thin films were investigated; the films were deposited on glass substrates by RF reactive-magnetron sputtering and post-annealed at 300 C in an oxygen atmosphere. Under similar deposition conditions, both films crystallized into hexagonal würzite lattice structures. The pure ZnO film exhibited a c-axis preferential orientation, whereas the Cedoped exhibited an a-axis preferential orientation. The films display uniform textured surfaces with columnar-like microstructures. The UV-Vis spectra showed high transparencies of 90 % on average for both films. Band gaps of E g ¼ 3:23 eV and E g ¼ 3:27 eV for pure and Ce-doped film, respectively, were measured. The doped film spectrum was shifted to the blue as a result of the Burstein-Moss effect. The XPS spectra show that the VB edge of the doped film shifts toward lower binding energy, at $ 1.3 eV below E F , while the VB edge of the pure film is located at $ 2.0 eV below E F . Additionally, Ce 3þ and Ce 4þ ions coexist in the ZnO matrix in fractions of $ 70 and $ 30 %, respectively. The PL spectra show that both types of ions induce extra electron states that allow multiple emission peaks in the blue-green region.

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Section: Characterization Techniquesmentioning

confidence: 93%

The influence of Ce doping on the structural and optoelectronic properties of RF-sputtered ZnO films

García-Méndez¹,

Segura

Coello

et al. 2015

Opt Quant Electron

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“…From a computational point of view, it is important to note that the standard DFT-GGA functionals such as PBE clearly underestimate the band gap of ZnO, typically predicting E gap = 0.9 eV in comparison to the experimental 0 K estimate of 3.44 eV. 45,46 This issue can be corrected by applying Hubbard-like corrections (PBE+U) or by applying hybrid density functionals where no semi-empirical corrections are necessary. Since we use the hybrid DFT-PBE0 functional, the band structure and band gap predicted for bulk ZnO are in very reasonable agreement with the experiment.…”

Section: Electronic Properties and Band Structure Engineeringmentioning

confidence: 99%

Atomic-Level Structural and Electronic Properties of Hybrid Inorganic–Organic ZnO:Hydroquinone Superlattices Fabricated by ALD/MLD

2015

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Ab initio calculationsWe investigate crystalline ZnO:hydroquinone (HQ) superlattices grown layer-by-layer by the combined atomic/molecular layer deposition (ALD/MLD) technique; such ALD/MLD layerengineered inorganic-organic thin films form a fundamentally new category of functional coherent hybrid materials that cannot be prepared by any other existing technique. Using quantum chemical methods, we derive atomic-level structural models for the ZnO:HQ superlattices and investigate their structural, spectroscopic, and electronic properties. By comparing the theoretical results with our experimental data we provide a detailed interpretation of experimentally measured infrared spectra, proving the presence of organic interfaces within the crystalline ZnO:HQ superlattices. We moreover show how the band structure of the hybrid material can be tailored by simple and experimentally feasible modifications of the organic constituent. The guidelines for the bandstructure engineering of ZnO:HQ superlattices should be valuable for the systematic enhancement and exploitation of the functional properties of ALD/MLD-grown inorganic-organic superlattices and nanolaminates in general.

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“…Vibrational calculations were performed using DFT linear response (DFPT). Raman intensities are estimated by the derivative of the dielectric susceptibility tensor with respect to the normal mode 82,83 . We have used DFPT for both the vibrations and the dielectric susceptibility and have performed the calculations using the vasp_raman.py package.…”

Section: (C) Genetic Algorithm (Gsgo)mentioning

confidence: 99%

Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

Caskey

Holder

Shulda

et al. 2016

The Journal of Chemical Physics

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Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for studies, since even simple binary non ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms. Here we report on experimental synthesis and characterization, as well as theoretical first-principles calculations of a previously unreported mixed-valent binary tin nitride. Thin film experiments indicate that this novel material is Ndeficient SnN with tin in the mixed II/IV valence state and a small low-symmetry unit cell. Theoretical calculations suggest that the most likely crystal structure has the space group 2 (SG2) related to the distorted delafossite (SG166), which is nearly 0.1 eV/atom above the ground state SnN polymorph. This observation is rationalized by the structural similarity of the SnN distorted delafossite to the chemically related Sn 3 N 4 spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of the metastable material. In addition to reporting on the discovery of the simple binary SnN compound, this paper illustrates a possible way of combining a wide range of advanced characterization techniques with the first-principle property calculation methods, to elucidate the most likely crystal structure of the previously unreported metastable materials. 2

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Dielectric properties and Raman spectra of ZnO from a first principles finite-differences/finite-fields approach

Cited by 121 publications

References 38 publications

The influence of Ce doping on the structural and optoelectronic properties of RF-sputtered ZnO films

The influence of Ce doping on the structural and optoelectronic properties of RF-sputtered ZnO films

Atomic-Level Structural and Electronic Properties of Hybrid Inorganic–Organic ZnO:Hydroquinone Superlattices Fabricated by ALD/MLD

Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

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