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Picosecond Luminescence Studies of Recombination Dynamics at GaAs/Electrolyte Interfaces
Published in Arthur T. Hubbard, The Handbook of Surface Imaging and Visualization, 2022
Geraldine L. Richmond, John F. Kauffman, Barbara A. Balko, Eric A. Miller
These results have important implications for the interpretation of experiments. Clearly the power of the excitation must be carefully monitored and held constant when comparing results under various experimental conditions. Because the photon count rate at the detector must be limited in time-correlated photon counting, it is often tempting to adjust the count rate by varying the excitation power. In studies of luminescence decays from semiconductors, this practice must be avoided. These results also bear on the use of high injection radiative decay profiles in the determination of interfacial charge transfer kinetics. The high injection condition is often employed to minimize effects due to space charge fields under open circuit conditions. According to our results, such studies tend to underestimate surface trap state populations due to the saturation. We note that measurements of STVs performed on clean GaAs surfaces compare most favorably with the highest-power results presented here. The lower-power results indicate clearly, however, that high-power STVs cannot be indiscriminately used as data for analysis of kinetics of charge transfer under nonsaturation conditions. This caution applies most notably to the analysis of semiconductor photoelectrochemical systems under solar irradiation.
Carbon Based Supercapacitors
Published in Ling Bing Kong, Nanomaterials for Supercapacitors, 2017
Ling Bing Kong, Wenxiu Que, Lang Liu, Freddy Yin Chiang Boey, Zhichuan J. Xu, Kun Zhou, Sean Li, Tianshu Zhang, Chuanhu Wang
Figure 3.50 shows the potential distribution at the basal layer of graphite at negative bias potential. The differential capacitance of a semiconductor interface was composed of three series components, i.e., (i) the capacitance of the space charge layer within the semiconductor, (ii) the capacitance of the compact double-layer and (iii) the capacitance of the diffuse ionic layer of the electrolyte. For an intrinsic semiconductor, the charge-carrier (hole or electron) densities are very low, which is similar to the case of an electrolyte solution at a very low concentration. As a consequence, the charge carriers would be away from the interface and extended into the bulk of the electrode over a large distance, which was inversely related to the charge carrier density. The charge distribution distance inside the basal orientation of the electrode was of the same order of magnitude as that the of diffusion layer as the electrolyte solutions are diluted.
Semiconductor Detectors
Published in Douglas S. McGregor, J. Kenneth Shultis, Radiation Detection, 2020
Douglas S. McGregor, J. Kenneth Shultis
Up until 1960, semiconductor detectors, then called “crystal counters”, were considered mostly a novelty for radiation detection and were not commercially produced. The main reason, as expressed by Price [1958, 1964], was that semiconductors were of “very little use because of the preponderance of advantages of the scintillation detectors”.3 A significant disadvantage of semiconductors at the time was the high level of background impurities and crystal defects. Under reverse bias, the impurities could become ionized, as explained in Sec. 15.3.5, and trapping of electrons or holes in the defect states would reduce the induced current. In both cases, space charge would be created which tends to counter the applied voltage and reduce both the electric field and the depletion region width. However, in 1960 while working for the General Electric Co. (GE), Erik M. Pell [1960a, 1960b] developed a method of introducing a compensating Li ion into Si that countered the effect of p-type dopants. The method included the application of Li material to a heated bulk Si sample and driving Li ions deep into the semiconductor with a strong electric field, a method known as “Li drifting”. The technique was successfully applied to Si [Pell 1960b; Elliot 1961; Blankenship and Borkowski 1962] and Ge crystals [Freck and Wakefield 1962; Tavendale 1963, 1966; Goulding and Hansen 1964; Goulding 1965, 1966], and allowed relatively thick depletion layers to be formed. It was this fundamental improvement that allowed semiconductors to become important radiation detectors, and Ge(Li) and Si(Li) detectors4 came into common use as high resolution gamma-ray and x-ray detectors.
Structural, electrical and dielectric studies of PVA based NaNO3 Polymer electrolytes for battery applications
Published in International Journal of Ambient Energy, 2023
M. Gnana Kiran, NK. Jyothi, M.C. Rao, S.K. Babu, P. Pardhasaradhi, G.R.K. Prasad, M.P. Rao, K. Samatha
The dielectric nature is measured using the following expression (Rajesh et al. 2019). The real part is ε1 (ω) represents the dielectric constant & ε11(ω) represents an energy loss. Figures 8 and 9 show the frequency dependence of ε1 (ω) and ε11(ω). In all given plots, ε1 (ω) and ε11(ω) values are high at low frequencies and decrease gradually at medium frequencies. Finally, show a constant value. The accumulation of charge carriers is called the space charge effect. It is also called space charge polarisation, confirmed by non-Debye nature (Reddy et al. 2019b). The permeability is high at low frequencies and appears constant at high frequencies. These changes are occurring due to the space charge effects only. Due to this reason, the dielectric constant decreases gradually. By increasing the frequency in the field direction, no extra ions are not distributed in the field path.
Experimental and numerical study of different metal contacts for perovskite solar cells
Published in Cogent Engineering, 2023
Mohammad Istiaque Hossain, Puvaneswaran Chelvanathan, G. Al Kubaisi, Said Mansour
Using the SCAPS-1D software, which was developed at the University of Gent, Belgium (Bal et al., 2022; Belarbi et al., 2022; Chawki et al., 2022; Hossain et al., 2015; Moulaoui et al., 2022; Qasim et al., 2022), we conducted numerical simulations of a PSC solar cell. This software employs a finite difference approach to solve the electron and hole drift-diffusion equations in position space to represent charge movement within the device, based on given input parameters (electrical and optical) for each layer of the device. At each mesh point in position space, a set of equations for carrier trapping and escape are solved in energy space. The potential profile across the device, which is space charge dependent, is modeled using Poisson’s equation, while the carrier continuity equations are used to calculate charge transport in the device. The TiO2/perovskite absorber layer/Spiro-OMETAD/metal contacts structure was employed for the numerical analysis, utilizing the data presented in Table 1.
Dielectric, electrical, magnetic, and mechanical properties of Ni-Al ferrite/PANI composite films
Published in Phase Transitions, 2022
Enas A. Arrasheed, O. M. Hemeda, Yamen A. Alibwaini, T. M. Meaz, Rizk Mostafa Shalaby, Abdul-Wali Ajlouni, A. M. A. Henaish, B. I. Salem
The frequency dependence spectra of M′, M″ and Cole–Cole (M′ vs M″) are shown in Figure 5. The M′ spectra show an almost linear increase, up to f = 107 Hz, where M′ values are higher for the sample of high Al content. At low frequencies, the values of M′ are non-zero, which confirms that the lower values of ϵ′ of the samples are free from the EP effect and the observed increase in M′ values completely agrees with the decrease in ϵ′ values. This may be referred to the charge transport and charge accumulation which is assumed a significant issue in electrical insulation, as the accumulation of space charge enhances the electric fields available in different places inside the composite, which will lead to partial electric discharges, i.e. dielectric breakdown.