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1	Structural, electronic and optical properties of cadmium sulfide nanoparticles / Strukturelle, elektronische und optische Eigenschaften von Cadmiumsulfid Nanoteilchen Frenzel, Johannes 08 March 2007 (has links) (PDF) In this work, the structural, electronic, and optical properties of CdS nanoparticles with sizes up to 4nm have been calculated using density-functional theory (DFT). Inaccuracies in the description of the unoccupied states of the applied density-functional based tight-binding method (DFTB) are overcome by a new SCF-DFTB method. Density-functional-based calculations employing linear-response theory have been performed on cadmium sulfide nanoparticles considering different stoichiometries, underlying crystal structures (zincblende, wurtzite, rocksalt), particle shapes (spherical, cuboctahedral, tetrahedral), and saturations (unsaturated, partly saturated, completely saturated). For saturated particles, the calculated onset excitations are strong excitonic. The quantum-confinement effect in the lowest excitation is visible as the excitation energy decreases towards the bulk band gap with increasing particle size. Dangling bonds at unsaturated surface atoms introduce trapped surface states which lie below the lowest excitations of the completely saturated particles. The molecular orbitals (MOs), that are participating in the excitonic excitations, show the shape of the angular momenta of a hydrogen atom (s, p). Zincblende- and wurtzite-derived particles show very similar spectra, whereas the spectra of rocksalt-derived particles are rather featureless. Particle shapes that confine the orbital wavefunctions strongly (tetrahedron) give rise to less pronounced spectra with lower oscillator strengths. Finally, a very good agreement of the calculated data to experimentally available spectra and excitation energies is found. PhD thesis Doktorarbeit TU-Dresden nanoparticles semiconductor quantum dot cadmium sulphide cadmium sulpfide surface structure electronic structure optical excitation density-functional theory DFT density-functional based tight-binding DFTB Doktorarbeit TU-Dresden Nanoteilchen Halbleiterquantenpunkt Cadmiumsulfid Oberflächenstruktur elektronische Struktur optische Anregung Dichtefunktionaltheorie DFT density-functional based tight-binding DFTB TD-DFT linear-response ddc:540 rvk:VE 9857 Nanopartikel Halbleiter Quantenpunkt Cadmiumsulfid Oberflächenstruktur Elektronenstruktur Photoanregung Dichtefunktionalformalismus
2	Structural, electronic and optical properties of cadmium sulfide nanoparticles Frenzel, Johannes 19 December 2006 (has links) In this work, the structural, electronic, and optical properties of CdS nanoparticles with sizes up to 4nm have been calculated using density-functional theory (DFT). Inaccuracies in the description of the unoccupied states of the applied density-functional based tight-binding method (DFTB) are overcome by a new SCF-DFTB method. Density-functional-based calculations employing linear-response theory have been performed on cadmium sulfide nanoparticles considering different stoichiometries, underlying crystal structures (zincblende, wurtzite, rocksalt), particle shapes (spherical, cuboctahedral, tetrahedral), and saturations (unsaturated, partly saturated, completely saturated). For saturated particles, the calculated onset excitations are strong excitonic. The quantum-confinement effect in the lowest excitation is visible as the excitation energy decreases towards the bulk band gap with increasing particle size. Dangling bonds at unsaturated surface atoms introduce trapped surface states which lie below the lowest excitations of the completely saturated particles. The molecular orbitals (MOs), that are participating in the excitonic excitations, show the shape of the angular momenta of a hydrogen atom (s, p). Zincblende- and wurtzite-derived particles show very similar spectra, whereas the spectra of rocksalt-derived particles are rather featureless. Particle shapes that confine the orbital wavefunctions strongly (tetrahedron) give rise to less pronounced spectra with lower oscillator strengths. Finally, a very good agreement of the calculated data to experimentally available spectra and excitation energies is found. info:eu-repo/classification/ddc/540 ddc:540

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Structural, electronic and optical properties of cadmium sulfide nanoparticles / Strukturelle, elektronische und optische Eigenschaften von Cadmiumsulfid Nanoteilchen

Structural, electronic and optical properties of cadmium sulfide nanoparticles