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Free electron model

About: Free electron model is a research topic. Over the lifetime, 4678 publications have been published within this topic receiving 103535 citations.


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TL;DR: In this article, the authors used the embedded cluster model of chemisorption for the problem of two hydrogen atoms on a free electron surface with simple derivation of the well known R−5 asymptotic behaviour for the interaction, at large inter-adatom distances R, compared to the corresponding R−3 behaviour for two impurities in a bulk free electron gas.

22 citations

Journal ArticleDOI
TL;DR: In this article, the frequency dependence of these losses was investigated using the microwave cavity perturbation (MCP) and broadband coaxial probe (BCP) methods, and it was shown that disorder related loss may dominate over free electron conduction from 1-10 GHz.
Abstract: Broadband microwave complex permittivity measurements of nanodiamond powders are presented. Previous studies show that measurements of dielectric loss strongly correlate with the presence of nondiamond surface impurities. In this study, the frequency dependence of these losses is investigated using the microwave cavity perturbation (MCP) and broadband coaxial probe (BCP) methods. This allowed further understanding as to what mechanisms contribute to the microwave absorption (free electron conduction or dielectric loss from the disordered surfaces). A multimode MCP system is used which utilizes ${\rm TM}_{0np}$ modes to provide partial spectral characterization. The MCP results revealed minimal frequency dependence, unlike any static conduction-related mechanism. The BCP measurements corroborate the MCP results with much higher spectral resolution, and further demonstrate that disorder related loss may dominate over free electron conduction from 1–10 GHz. From 0.1–1 GHz, free electron conduction has a greater influence with a characteristic $1/f$ dependence implying that conduction may dominate at lower frequencies. However, the BCP method, while repeatable, lacks in precision compared to the cavity method. Nonetheless, the major conclusion in this paper is that through simple microwave permittivity measurements, nondiamond carbon impurities in nanodiamond powders are measurable most likely because of disorder related losses as opposed to free electron conduction.

22 citations

Journal ArticleDOI
TL;DR: The photoluminescence of single InAs/GaAs self-assembled quantum dots for a range of excitation powers, excitation energies and sample temperatures 4 K30 K was studied in this paper.
Abstract: We study the photoluminescence of single InAs/GaAs self-assembled quantum dots for a range of excitation powers, excitation energies and sample temperatures 4 K30 K), this effect vanishes due to the essential decrease of the steady-state free electron concentration in the GaAs barrier as a result of thermally excited free holes appearing in the GaAs barrier valence band which provides an effective recombination channel for the free electrons. These experimental observations could be used as an effective tool to create and study charged excitons in quantum dots.

22 citations

Journal ArticleDOI
TL;DR: In this article, a soundwave-like collective excitation in Au atom chains on the Si(557) surface is investigated, and a significant change in the plasmon dispersion in a tiny momentum and energy region, which definitely reflects a gap opening due to a metal-to-insulator transition of the atom chains.
Abstract: Sound-wave-like collective excitation in Au atom chains on the Si(557) surface is investigated. Electron scattering spectroscopy using a highly collimated slow electron beam has detected a characteristic low-energy one-dimensional (1D) plasmon (wire plasmon) that is confined in the atom chains. Theoretical analysis adopting a quantum-mechanical scheme beyond the free-electron model indicates a significant dynamic exchange-correlation effect due to strong 1D confinement. By cooling to below 100 K, we have detected for the first time a significant change in the plasmon dispersion in a tiny momentum and energy region, which definitely reflects a gap opening due to a metal-to-insulator transition of the atom chains.

22 citations

Journal ArticleDOI
TL;DR: In this article, the authors model the optical and electrical power transmission through transparent conducting oxide (TCO) layers in thin-film solar cells as a function of both the electron carrier density, n, and its mobility, μ.
Abstract: The performance of thin-film solar cells is critically dependent upon the effective operation of transparent conducting oxide (TCO) layers, which play a significant role in both optical and electrical power transmission through these photovoltaic devices. In this article, we model the optical and electrical power transmission through TCO layers in thin-film solar cells as a function of both the electron carrier density, n, and its mobility, μ. The electrical and optical properties of the TCO layer are described by the simple Drude model of the degenerate free electron gas and the concomitant electromagnetic absorption due to skin-depth effects is thereby calculated. Above the critical carrier density for the composition-induced Mott Insulator-Conductor Transition, TCOs exhibit metallic-type conduction. However, with increasing electron (carrier) density above the transition, the optical transparency of the layer is significantly decreased. Importantly, in order to achieve high electrical conductivity whilst preserving high optical transparency of the TCO layer, electron mobilities need to be increased in preference to increasing electron densities. To reach higher carrier mobilities in any given TCO system, we propose that one should move the material close to the Mott transition. A model of ionized impurity scattering in indium tin oxide (ITO) at high carrier densities allows direct comparison of the μ-n relationship in real TCO layers to the total power absorption in such layers in thin-film solar devices. We determine that decreasing the electron density from 2.6 × 1021 cm−3 to 2 × 1021 cm−3 in such an ITO layer above the Mott critical density can decrease the total power absorption in the layer by a large amount (around 8% relative to the minimum theoretical absorption).

22 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202340
202290
2021132
2020122
2019114
2018112