Optical Bandgap Definition via a Modified Form of Urbach’s Rule

Bhowmick, Mithun; Xi, Haowen

doi:10.3390/ma14071639

Cited by 10 publications

(4 citation statements)

References 17 publications

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“…Since the c domains are polarized in either upward ( c + ) or downward ( c – ) direction with respect to the a–b plane of the crystal, the induced charges on the surface lead to a higher surface and electrostatic energy as compared to those in the a domains. Polar H 2 O molecules prefer to adsorb on the c domain to neutralize the surface charge, whereas the a domain has no surface charges. − The chemisorbed water droplets create sub-band gap states, leading to the inarticulate band gap energy values reported in the literature from 1.81 to 3.4 eV in its ferroelectric ground state. − The existence of sub-band gap states allows the absorption of visible light by the c domains of BTO dominantly (see Supporting Information S6), and hence the photo-voltaic effect occurs. Whereas, a domains show lesser sensitivity to the visible light illumination.…”

Section: Discussionmentioning

confidence: 99%

Amalgamation of Photostriction, Photodomain, and Photopolarization Effects in BaTiO₃ and Its Electronic Origin

Bagri

Jana

Panchal

et al. 2022

ACS Appl. Electron. Mater.

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Multifunctional oxides offer huge potential for technological applications, owing to their inclusive physical properties such as ferroelectric, piezoelectric, and electro-caloric properties. The natural occurrence of piezoelectricity, a tunable band gap of ferroelectrics, opens a path to study the light–material interaction, leading to photoconduction and photovoltaic effects. Such light-controlled devices yield additional advantages of weight reduction and wireless, remote-controlled functionality over the heavy electric circuitry and, hence, are projected as an alternative solution to the traditional piezoelectric-based devices. Among these materials, lead-free BaTiO3-based ferroelectric materials are a good choice for their potential applications with recently discovered light-controlled functionality. However, until now, the coupling of light with the chemistry of ferroelectricity of BaTiO3 crystals has been elusive, although the ferroelectricity and piezoelectricity are well-studied. Here, the present study reports the photostrictive effect of the order of 10–4 on the dimension of the c domains of tetragonal BaTiO3 crystals and domain reorientation at room temperature under unpolarized, coherent visible light illumination, consequently resulting in enhancement in polarization. The electronic origin of domain evolution and photostriction is explained by the light-induced modification in the Ti 3d–O 2p-hybridized orbitals. This facilitates the perspective of combining mechanical, electrical, optical, and functionalities in future generations of remote-controlled devices.

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Section: Discussionmentioning

confidence: 99%

Amalgamation of Photostriction, Photodomain, and Photopolarization Effects in BaTiO₃ and Its Electronic Origin

Bagri

Jana

Panchal

et al. 2022

ACS Appl. Electron. Mater.

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“…Additionally, the Urbach rule itself is an empirical formula used to describe the exponential absorption near the band-edge. This can be changed accordingly to improve the description or even to determine the optical bandgap [63].…”

Section: Urbach Slopementioning

confidence: 99%

New optical dispersion models for the accurate description of the electrical permittivity in direct and indirect semiconductors

Lizárraga,

Enrique-Morán,

Tejada

et al. 2023

J. Phys. D: Appl. Phys.

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We propose new optical dispersion models to describe the imaginary part of the electrical permittivity of dielectric and semiconductor materials in the fundamental absorption region. We work out our procedure based on the well-known structure of the semi-empirical Tauc-Lorentz dispersion model and the band-fluctuations approach to derive a 5-parameter formula that describes the Urbach, Tauc and high-absorption regions of direct and indirect semiconductors. Main features of the dispersion models are the self-consistent generation of the exponential Urbach tail below the bandgap and the incorporation of the Lorentz oscillator behavior due to electronic transitions above the fundamental region. We apply and test these models on optical data of direct (MAPbI3, GaAs and InP), indirect (GaP and c-Si), and amorphous (a-Si:H) semiconductors, accurately describing the spectra of the imaginary part of the electrical permittivity. Lastly, we compare our results with other similarly inspired dispersion models to assess the optical bandgap, Urbach tail and oscillator central resonance energy.

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“…The absorption edge becomes wide for polycrystalline and amorphous semiconductors because allowed localized states are found in the energy gap. The width of these localized states can be calculated using Urbach Rule [36] α= α0𝑒…”

Section: Uv-vis Propertiesmentioning

confidence: 99%

Effect of Annealing Times on the Structural and Optical Properties of PbO Thin Films Prepared by D.C Sputtering

Rauuf

Aadim

2023

Iraqi Journal of Science

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In this work, lead oxide (PbO) thin films were deposited using D.C. sputtering method on a surface of glass substrates and then thermally annealed at a temperature of 473K with annealing times of (1,2 and 3) hours. The structural, morphological, and optical properties of films were determined using X-ray diffraction (XRD), atomic force microscopy (AFM), FT-IR, and UV-Visible spectroscopy. The structure studies confirmed that PbO films are polycrystalline structures in an orthorhombic phase with average grain size (24.51, 29.64, 46.49, 16) nm with increasing annealing time. From AFM, the roughness of the film surface (3.26, 1.76, 1.61, 1.79) nm as the film annealing time increases. The optical band gap values of the PbO thin films are (3.9, 2.8, 3.7, 2.4) eV as the annealing time increases.

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Optical Bandgap Definition via a Modified Form of Urbach’s Rule

Cited by 10 publications

References 17 publications

Amalgamation of Photostriction, Photodomain, and Photopolarization Effects in BaTiO₃ and Its Electronic Origin

Amalgamation of Photostriction, Photodomain, and Photopolarization Effects in BaTiO₃ and Its Electronic Origin

New optical dispersion models for the accurate description of the electrical permittivity in direct and indirect semiconductors

Effect of Annealing Times on the Structural and Optical Properties of PbO Thin Films Prepared by D.C Sputtering

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Optical Bandgap Definition via a Modified Form of Urbach’s Rule

Cited by 10 publications

References 17 publications

Amalgamation of Photostriction, Photodomain, and Photopolarization Effects in BaTiO3 and Its Electronic Origin

Amalgamation of Photostriction, Photodomain, and Photopolarization Effects in BaTiO3 and Its Electronic Origin

New optical dispersion models for the accurate description of the electrical permittivity in direct and indirect semiconductors

Effect of Annealing Times on the Structural and Optical Properties of PbO Thin Films Prepared by D.C Sputtering

Contact Info

Product

Resources

About

Amalgamation of Photostriction, Photodomain, and Photopolarization Effects in BaTiO₃ and Its Electronic Origin

Amalgamation of Photostriction, Photodomain, and Photopolarization Effects in BaTiO₃ and Its Electronic Origin