Optical Transitions in Artificial Few-Electron Atoms Strongly Confined inside ZnO Nanocrystals

Abstract

We have studied the optical transitions in artificial atoms consisting of one to ten electrons occupying the conduction levels in ZnO nanocrystals. We analyzed near IR absorption spectra of assemblies of weakly coupled ZnO nanocrystals for a gradually increasing electron number and found four allowed dipole transitions with oscillator strengths in quantitative agreement with tight-binding theory. Furthermore, this spectroscopy provides the single-particle energy separation between the conduction levels of the ZnO quantum dots.

Third harmonic and sum-frequency generation in ZnO quantum dots

“…The transition matrix product involved in the two coupling schemes are D 1 = F 4 (Z 1S-2P Z 2P-2S Z 2S-1P Z 1P-1S ) and D 2 = F 4 (Z 1S-2P Z 2P-1D Z 1D-1P Z 1P-1S ) respectively. In our earlier studies [34] the estimated transition energies for the quantum confined states in singly charged ZnO QD are found in good agreement with experimental data of Germeau et al [35] (Fig. 2 of Ref.…”

Quantum size effects in ZnO nanowires

“…[1] for a review), only rather simple theoretical studies of ZnO nanowires exist [6,7]. In contrast, comprehensive theoretical studies of ZnO nanocrystals have been published [8,9] and the effect of reduced size on band gap and level splittings has been analyzed. For nanowires, however, accurate theoretical estimates of quantum size effects on band gaps etc.…”

“…The usual effective-mass approximation assuming infinite barriers is known to severely overestimate the correction to the band gap. For this reason we apply a more reliable tightbinding approach similarly to the nanocrystal studies [8,9]. Exciton binding energies can also be calculated from an expansion of electron-hole pair states in tight-binding states as done for e.g.…”

Double quantum dot photoluminescence mediated by incoherent reversible energy transport

“…Finally, the pair can relax to the lowest-energy state ͉1A͘ of the QD acceptor due to intraband transition at a rate 1A,2A . This rate is determined by both radiative 52 and nonradiative 12,19,23,26,28 intraband transitions. In the final stage of the scenario under consideration, there are two channels of the ͉1A͘-state relaxation.…”