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Fundamentals of Nanotechnology
Published in Grunwald Peter, Biocatalysis and Nanotechnology, 2017
Torben Kodanek, Sara Sánchez Paradinas, Franziska Lübkemann, Dirk Dorfs, Nadja C. Bigall
Equation 1.2 Brus equation for calculating the energy band gap Egap of a quantum dot as a function of its radius (r). Necessary material constants are the effective masses of the charge carriers (me∗ $ m_{e}^{*} $ and mh∗ $ m_{h}^{*} $ ) in the material, the relative permittivity (ɛr) of the material and the bulk band gap of the material (Egap(bulk)).
Materials for Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
What is a QD? Why is it called an “artificial atom?” Write the Brus equation for the difference in bandgap in a QD and a bulk semiconductor. Explain the symbols used and provide the interpretation of the three terms in the equation. Which is the dominant term in energy change?
Oxidation behavior with quantum dots formation from amorphous GaAs thin films
Published in Philosophical Magazine, 2018
Srikanta Palei, Bhaskar Parida, Keunjoo Kim
The GaAs crystal has the band gap of 1.42 eV, and gallium oxide has large bandgap energy of around 4.9 eV [3]. It has been reported that arsenolites of cubic arsenic oxide have optical PL peaks at 548 nm (2.26 eV), 615 nm (2.016 eV), and 505 (2.45) −650 nm (1.90 eV) in the near-field photoluminescence measurements [10,11]. These PL spectra are related to defect centres in the band gap region. However, the calculated bandgap of arsenolite by first-principles lattice-dynamics calculations is 3.64 eV for <100> and 4.01 eV for <111> directions in the dynamically stable low-symmetry structures, where valence electrons localise and form a lone pair of cations [33]. The band gap of 2.73 eV from UPS-IPS data and large PL emission energy of 3.0 eV are not consistent with the energy structures of oxides. However, it is valuable to analyze the quantum size effect for both band gap energy and PL emission energy. The emission energy from the GaAs quantum dot is expressed by the Brus equation of effective mass approximation (EMA) [34]: , where R is radius, is the bulk band gap energy of 1.42 eV, and are the effective electron and hole masses of 0.063 and 0.51 , respectively. Therefore, from GaAs quantum dot equation of , the PL energy of 2.41–2.75 eV corresponded to a dot diameter of 4.48–5.19 nm and the energy band gap of 2.73 eV corresponded to the diameter of 4.52 nm. These results are consistent with the TEM image shown in Figure 3(d).