Energy Band Structure of Lithium Fluoride Crystals by the Method of Tight Binding

Chaney, Roy C.; Lafon, Earl E.; Lin, Chun C.

doi:10.1103/physrevb.4.2734

Cited by 92 publications

(15 citation statements)

References 18 publications

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“…The crystalline form of LiF is an insulator with the highest UV transmission and largest band gap E g for of any material. However, different values for its band gap, determined experimentally and theoretically, have been reported in the literature, ranging from ∼8 to 16 eV [42,43] . Figures 7(a) and (b) shows the fits of equations (21) and (22) for n E ( ) and k E ( ) to the experimental data of LiF published by Palik and Hunter [35].…”

Section: Lithium Fluoride (Lif)mentioning

confidence: 99%

New dispersion equations for insulators and semiconductors valid throughout radio-waves to extreme ultraviolet spectral range

Forouhi

Bloomer

2019

J. Phys. Commun.

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A new formulation of optical dispersion in terms of complex index of refraction, N(E) as a function of photon energy, E, applicable to insulators and semiconductors, is introduced. Previous formulations, developed over the past 200 years, are either valid only over a limited spectral range, or do not accurately fit experimental data, or do not conform to the Principle of Causality. The new formulation overcomes these shortcomings. Its validity is established based on theoretical and experimental considerations. The theoretical basis stems from consistency with Titchmarsh's Theorem, a comprehensive mathematical expression of the Principle of Causality. In accordance with Titchmarsh's Theorem, the expressions for the real and imaginary parts of N(E), the refractive index, n(E), and extinction coefficient, k(E), are shown to be skew reciprocal Hilbert Transforms. Also, the expression for the inverse Fourier Transform of N(E) is shown to be a complex-valued causal function of time. The causal function is identified as the polarization of the medium, P(t), if photons reach the medium at an initial time equal to zero. P(t) is associated with photon excitations of electrons and other quantum constituents of the media. The experimental basis of the formulation stems from demonstrating exceptionally close agreement with published experimental n(E) and k(E) data of different forms of insulators and semiconductors. Specifically, the formulation is applied to data of Water, Ice, SiO 2 -Glass, LiF, Polyethylene, a-Si, InSb, GaP, and As 2 Se 3 . Data for Water span thirteen orders of magnitude, and fourteen for Ice, over the spectral range of Radio-Waves to EUV. Data of the other materials involved smaller spectral ranges. Results indicate that fewer fitting parameters are needed over any segment of the electromagnetic spectrum, compared to other formulations. These theoretical and experimental findings suggest the formulation represents a universal description of optical dispersion of insulators and semiconductors.

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Section: Lithium Fluoride (Lif)mentioning

confidence: 99%

New dispersion equations for insulators and semiconductors valid throughout radio-waves to extreme ultraviolet spectral range

Forouhi

Bloomer

2019

J. Phys. Commun.

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“…LiF is one of the promising engineered SEI coating materials on the electrodes (e.g., Si) of LIBs, since the improved performance of electrodes has been linked to the increased concentration of LiF in the natural SEI. [41][42][43][44][45][46][47]57 In addition, perfect LiF crystals have a wide band gap [58][59][60] , and can thus block the electron leakage to the electrolyte from the electrodes. In the present work, as a development of a general approach to evaluate all possible point defects, we studied ionic conductivity of a total of seventeen possible native defects with their relevant charge states in LiF on the surface of different electrodes.…”

Section: -47mentioning

confidence: 99%

General method to predict voltage-dependent ionic conduction in a solid electrolyte coating on electrodes

2015

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Understanding the ionic conduction in solid electrolytes in contact with electrodes is vitally important to many applications, such as lithium ion batteries. The problem is complex because both the internal properties of the materials (e.g., electronic structure) and the characteristics of the externally contacting phases (e.g., voltage of the electrode) affect defect formation and transport. In this paper, we developed a method based on Density Functional Theory to study the physics of defects in a solid electrolyte in equilibrium with an external environment. This method was then applied to predict the ionic conduction in lithium fluoride (LiF), in contact with different electrodes which serve as reservoirs with adjustable Li chemical potential (µLi) for defect formation. LiF was chosen because it is a major component in the solid electrolyte interphase (SEI) formed on lithium ion battery electrodes. Seventeen possible native defects with their relevant charge states in LiF were investigated to determine the dominant defect types on various electrodes. The diffusion barrier of dominant defects was calculated by the Climbed Nudged Elastic Band Method. The ionic conductivity was then obtained from the concentration and mobility of defects using the Nernst-Einstein relationship. Three regions for defect formation were identified as a function of µLi: 1) intrinsic, 2) transitional, and 3) p-type region. In the intrinsic region (high µLi, typical for LiF on the negative electrode), the main defects are Schottky pairs and in the p-type region (low µLi, typical for LiF on the positive electrode) are Li ion vacancies. The ionic conductivity is calculated to be approximately 10 −31 Scm −1 when LiF is in contact with a negative electrode but it can increase to 10Scm −1 on a positive electrode. This new insight suggests that divalent cation (e.g., Mg 2+ ) doping is necessary to improve Li ion transport through the engineered LiF coating, especially for LiF on negative electrodes. Our results provide a new understanding of the influence of the environment on defect formation and demonstrate a linkage between defect concentration in a solid electrolyte and the voltage of the electrode.

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“…In this study, we demonstrate an AC-driven OLED, with lithium fluoride (LiF) as its insulating layer using a simple thermal evaporation process. The thermally deposited LiF exhibits excellent insulation and capacitance for its wide band gap 18 and relatively high k 19 compared to SiO 2 , and is more easily processed along with organic materials 20 . Ultraviolet photoelectron spectroscopy (UPS) and inverse photoemission spectroscopy (IPES) are employed to examine the electronic band structure of AC-driven OLEDs to explore the operation mechanisms.…”

mentioning

confidence: 99%

Alternating Current Driven Organic Light Emitting Diodes Using Lithium Fluoride Insulating Layers

Liu

Chang

et al. 2014

Sci Rep

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We demonstrate an alternating current (AC)-driven organic light emitting diodes (OLED) with lithium fluoride (LiF) insulating layers fabricated using simple thermal evaporation. Thermal evaporated LiF provides high stability and excellent capacitance for insulating layers in AC devices. The device requires a relatively low turn-on voltage of 7.1 V with maximum luminance of 87 cd/m2 obtained at 10 kHz and 15 Vrms. Ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy are employed simultaneously to examine the electronic band structure of the materials in AC-driven OLED and to elucidate the operating mechanism, optical properties and electrical characteristics. The time-resolved luminance is also used to verify the device performance when driven by AC voltage.

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Energy Band Structure of Lithium Fluoride Crystals by the Method of Tight Binding

Cited by 92 publications

References 18 publications

New dispersion equations for insulators and semiconductors valid throughout radio-waves to extreme ultraviolet spectral range

New dispersion equations for insulators and semiconductors valid throughout radio-waves to extreme ultraviolet spectral range

General method to predict voltage-dependent ionic conduction in a solid electrolyte coating on electrodes

Alternating Current Driven Organic Light Emitting Diodes Using Lithium Fluoride Insulating Layers

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