PHYS 284 |
| We have previously reported that, in general, the band gaps in quantum wires should be significantly smaller than those in the corresponding quantum dots of equal diameter, and have presented an effective-mass-approximation, particle-in-a-box (EMA-PIB) model to describe semi-quantitatively the shape dependence of quantum confinement. In contradiction to this model, we now report that the band gaps in colloidal CdTe quantum wires and quantum dots having diameters in the range of 5 – 11 nm are experimentally indistinguishable. Analysis at higher levels of theory establishes that a threshold diameter exists, below which the EMA-PIB model for the scaling of semiconductor quantum-wire and quantum-dot band gaps is approximately valid, but above which the quantum-wire and quantum-dot band gaps are extremely close. For CdTe, the threshold diameter is 5 nm. We will show that the value of the threshold diameter for semiconductor quantum wires and dots depends on the strength of the Coulomb interaction between electrons and holes. Additionally, the absorption spectra of the CdTe quantum wires are rich in detail, and allow determination of the diameter dependence of higher-lying excited states in the wires. These are theoretically analyzed and assigned. |
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Nanostructured Materials
1:20 PM-5:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Rm. 338, Oral
Division of Physical Chemistry |