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Binding Energies and Linear and Nonlinear Optical Properties of a Donor Impurity in a Three-Dimensional Quantum Pseudodot Muharrem Kiraka and Sait Yilmazb a Department of Science Education, Faculty of Education, Bozok University, 66200 Yozgat, Turkey b Department of Physics, Faculty of Arts and Sciences, Bozok University, 66200 Yozgat, Turkey Reprint requests to M. K.; E-mail: muharrem.kirak@bozok.edu.tr Z. Naturforsch. 68a, 744 – 750 (2013) / DOI: 10.5560/ZNA.2013-0053 Received December 5, 2012 / revised July 11, 2013 / published online September 18, 2013 A

Abstract

The problem of a shallow donor impurity located at the centre of a symmetrical paraboloidal quantum dot (SPQD) is solved exactly. The Schrödinger equation is separated in the paraboloidal coordinate system. Three different cases are discussed for the radial-like equations. For a bound donor, the energy is negative and the solutions are described by Whittaker functions. For a non-bound donor, the energy is positive and the solutions become coulomb wave functions. In the last case, the energy is equal to zero and the solutions reduce to Bessel functions. Using the boundary conditions at the dot surfaces, the variations of the donor kinetic and potential energies versus the size of the dot are obtained. The problem of a shallow donor impurity in a Hemiparaboloidal Quantum dot (HPQD) is also studied. It is shown that the wave functions of a HPQD are specific linear combinations of those of a SPQD.

throughput light power I@ and deflected light power I@ are performed in the far- field pattern of the output end-face using a photodetec- tor. After some amplification the signal can be passed to a X — Υ recorder, or to an oscilloscope. First, some comments should be made on the dc drift phenomena of the guided light. It is well known that the laser transmission in LiNbO3 waveguides photoionizes donor impurities, such as divalent iron, and induces charge separation along the crystal's polar axis [6]. When an external electric field Ε is applied in the wave- guide, the

-film material, expensive RuOz and silver powders are often added in order to eliminate non-ohmic contact and reduce room temperature resistivity. But we used micro (Vi.xCrx)203 instead. Not only the costs were cut down but also the room temperature resistivity was reduced. The accuracy and R-T curve linearity were improved as well. So better effect was achieved. That was another feature of this study. 5) In this study, Y 2 0 3 was not only the donor impurity, which made Ba,.xSrxTi03 semiconductive, but also a kind of stabilizer'51, which stopped the grains from

, Cd and Ta, it is plausible that Sc 3 + , C d 2 + and Ta 5 + are realized in T i 0 2 . To make the situation more clear, we now consider the electronic structure of the T i 0 2 matrix with impu- rities. The schematic band-structure of pure T i 0 2 is shown in Figure 2. The Fermi level (8y) of pure T i 0 2 sits in the band gap. The valence band is mainly from the oxygen p-states, and the conduction band is mainly from the metal d-states. Nb atom and Ta atom has one more valence electron than Ti atom. When such donor impurities are introduced in this matrix

EU PVSEC; 2010 6 – 10 Sept; Valencia, Spain. [20] J. Haunschild, J. Broisch, I. Reis, S. Rein. Quality control of czochralski grown silicon wafers in solar cell production using photoluminescence imaging. Proc 26th EU PVSEC; 2011 5 – 9 Sept; Hamburg, Germany. [21] A. S. Grove, O. Leistiko, C. T. Sah. Redistribution of acceptor and donor impurities during thermal oxidation of silicon. J Appl Phys. 1964;35(9):2695 – 2701. [22] J.-F. Nekarda, M. Hörteis, F. Lottspeich, A. Wolf, R. Preu. Comparison of the three different metallization concepts 176   B

in Green

. Rev. 92, 943 (1953). 11. Wolf, H., Deubler, S., Forkel, D., Foettinger, H., Iwatschenko- Borho, M., Meyer, F., Renn, M., Witthuhn, W., Helbig, R.: Accep- tors and Donors in the Wide-Gap Semiconductors ZnO and SnO2. Mater. Sci. Forum 10–12, 863 (1986). 12. Deubler, S., Meier, J., Schütz, R., Witthuhn, W.: PAC Studies on Impurities in ZnO. Nucl. Instrum. Meth. Phys. Res. B 63, 223 (1992). 13. For the origin of the fast damping in the spectra of Al-doped ZnO, we should take into consideration the effect of a presumed local spin provided by the donor impurities

contact to the solution that is only saturated with respect to the other component of the hetero- junction. There is a limited range of solid solubility between InP and CdS38 and the coprecipitation of both materials during the later stages of the cooling cycle leads to mixed epilayers with undesirable properties for solar cell applications. Cd and Sn dissolve InP much more readily than CdS and are thus suitable solvents for liquid phase epitaxy of InP on CdS substrates. However, only Cd generates p-type conduc- tivity while Sn is a donor impurity in InP and pure Sn is

. 1991). The α-Fe2O3 specimens containing donor impurities are n-type semiconductors at low temperature because conduc- tion band electrons are much more mobile as charge carriers than are valence band holes at room temperature (Goodenough 1972; Leland and Bard 1987; Anderman and Kennedy 1988; Merchant et al. 1979). Except where stated, all samples were imaged in air after immersion in water to help ensure that the surface was hydrated. Samples were dried by touching a Kimwipe the crystal edge to wick bulk water away. Because of drift and other problems (Eggleston 1994

electron to the conduction band of the crystal, in a manner analogous to a donor impurity atom in a semi- conductor, or to an F' center in an alkali halide23. To be a little more specific, one could think of this ionization as the trapping of a positive hole. If on recoil an electron transfer took place Recoil Co*++ + CO(NH3)„+++ + NO,- ^ Co++ + Co*(NH3)e++ + NO3° or Recoil Br*" + Co(NH3)5Br++ -> Br° + Co(NH3)5Br*+ then one would have a defect (the complex ion of cobalt [II]) and a nearby positive hole (Br° or N 0 3 ° ) so tha t on supplying the necessary