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Review of Solid State Physics
Published in Douglas S. McGregor, J. Kenneth Shultis, Radiation Detection, 2020
Douglas S. McGregor, J. Kenneth Shultis
Solid state materials used for radiation detectors are generally composed of crystalline materials. A crystalline material is defined by a basis of atoms arranged upon a periodic lattice. There are 14 possible Bravais lattice systems. The periodic arrangement of atoms causes the appearance of periodic potentials. This potential periodicity causes bands of allowed states to form, producing quasi-continua of energy states in these bands. The density of allowed energy states in these bands is defined by the density of states function. Gaps between these bands are referred to as energy gaps. The energy band that plays the part of atomic bonding is the valence band, and the energy band that plays the part in electron conduction is the conduction band. The energy gap between the valence band and the conduction band is referred to as the band gap.
Thermistor Probes
Published in John V. Twork, Alexander M. Yacynych, Sensors in Bioprocess Control, 2020
Response of thermistors to temperature change follows classical semiconductor theory. In the solid, the conduction band and the valence band are separated by a relatively small energy gap. This energy gap is small enough that changes in temperature will significantly change the number of electrons energetic enough to enter the conduction band. An increase in temperature increases the number of electrons in the conduction band and therefore decreases the resistance of the thermistor bead. This is adequately described by the equation [8] R1R2=expB(1T1−1T2)
Introduction
Published in John E. Ayers, Heteroepitaxy of Semiconductors, 2018
Heteroepitaxy, or the single-crystal growth of one semiconductor on another, is necessary for the development of a wide range of devices and systems. There are three motivations for semiconductor heteroepitaxy: substrate engineering, heterojunction devices, and device integration. Figure 1.1 and Figure 1.2 illustrate some of the wide range of semiconductor materials, all having unique properties that make them interesting for device applications. Of special importance is the energy gap, which determines the emission wavelength in light-emitting diodes and lasers, as well as the suitability for other device applications. In most cases, the combination of materials with different energy gaps will require mismatched heteroepitaxy due to the different lattice constants.
Modeling optical energy gap of thin film cuprous oxide semiconductor using swarm intelligent computational method
Published in Cogent Engineering, 2022
Talal F. Qahtan, Nahier Aldhafferi, Abdullah Alqahtani, Olawusi Richard Abidemi, Miloud Souiyah, Abdullah Almurayh, Fahad A. Alghamdi, Taoreed O. Owolabi
Cuprous oxide is characterized with simple crystal cubic crystallographic structure with p-type conductivity and direct energy gap of 2.17 eV (Hssi et al., 2020). It has a cubic structure with super-imposition of two sub-lattices which include copper cations (face centered cubic sub-lattice) and oxygen anions (body centered cubic sub-lattice). The copper atom is co-ordinated linearly by two neighboring oxygen atoms while the tetrahedral interstitial positions are occupied by the oxygen atoms in relation to with the copper sub-lattice (Moharam et al., 2016). Although, direct explanation of the nature of it p-type conductivity still remains unclear while oxygen interstitials has been attributed to the observed conduction in the semiconductor (L. Zhang et al., 2013). The two most common experimental methods of determining energy gap of semiconductors include measurement of photoluminescence spectra and measurement of spectra dependence of the absorption coefficient (Jafari et al., 2020). However, accurate energy gap determination requires advanced approach with utilization of x-ray photoelectron spectroscopy to measure the top of the valence band while the bottom of the conduction band is determined using inverse photoelectron spectroscopy (Chen et al., 2016). This advanced approach requires expensive, specialized and sophisticated equipment. Hybridization of particle swarm optimization algorithm and support vector regression is presented in this contribution for effective and precise characterization of cuprous oxide energy gap with appreciable quickness and reduced cost coupled with experimental difficulty circumvention.
Electronic structure of hydroxylated La@C82 endohedral metallofullerene: implications on photovoltaic cells
Published in Molecular Physics, 2020
Z. N. Cisneros-García, David Alejandro Hernández, Francisco J. Tenorio, J. G. Rodríguez-Zavala
Absorbing in wavelengths in visible spectrum is crucial, therefore, it is advantageous to have molecular structures with an energy gap value between 1.59 eV and 3.26 eV, which corresponds to visible solar spectrum. La@COH and La@COH seem to be the most adequate structures for possible use as solar energy materials, from energy gap point of view. Additionally, the energy gaps have the largest values with odd coatings and it can be understood since odd coatings have closed-shell (doublets) electronic configurations.
Effect of chalcone moiety on AC conductance of Metal Oxide Nano Composite doped thin polymer film
Published in Smart Science, 2023
B. Ayyanar, J. Suresh, V. Thangaraj, S. Karthikeyan, A. Arun, M. Kayalvizhi
The impedance plot is obtained by plotting imaginary part Z versus the real part Z data obtained for the prepared films B1AC1 and E1AC1 at room temperature. The entire prepared film impedance graph shows a semicircle at room temperature, but at higher temperatures the semicircle vanishes, which proves that there is no resistance at elevated temperatures [9]. The doping metal ions produce additional energy levels in the forbidden energy gap. When the temperature increases, the doped transition metal ions present in the polymer matrix get easily excited, which in turn generates a greater number of free electrons. So conductivity is greater at elevated temperatures. It is concluded that the doping improves the electrical conductivity.