Abstract
The molecular structures of , , and clusters in the ground state as well as in the lowest singlet and triplet excited states have been studied at the density-functional theory level using the first-order linear-response-theory approach for the singlet excited state. Structural changes compared to the ground state due to Franck-Condon relaxation of the singlet excited state are small, whereas optimization of the lowest triplet state is found to result in a dissociation of a bond. The electronic excitation spectra up to for the ground-state and excited-state structures of the silicon nanoclusters are also reported. The obtained Franck-Condon shift for the first excited state of is , yielding a luminescence energy of which is in good agreement with experimental data. The Franck-Condon shifts for and are found to be 1.17 and , yielding emission energies of 1.57 and , respectively, which are significantly smaller than the experimental value of about . Thus, the present study supports the notion that the silicon nanoclusters fabricated through electrochemical etching consist of 29 Si atoms surrounded by 36 hydrogen atoms.
1 More- Received 15 February 2005
DOI:https://doi.org/10.1103/PhysRevB.72.085424
©2005 American Physical Society