Structural and optical properties of passivated silicon nanoclusters with different shapes: A theoretical investigation

CCUR > College of Natural Science and Engineering > College of Science > Department of Physics > journal articles > Item 987654321/2549

Please use this identifier to cite or link to this item: https://irlib.pccu.edu.tw/handle/987654321/2549

Title:	Structural and optical properties of passivated silicon nanoclusters with different shapes: A theoretical investigation
Authors:	Wang, Bo-Cheng;Chou, Yu-Ma;Deng, Jin-Pei;Dung, Yu-Tsai
Contributors:	物理系
Date:	2008
Issue Date:	2009-11-06 13:33:15 (UTC+8)
Abstract:	Optimized geometries and electronic structures of hydrogenated silicon nanoclusters, which include the T-d and I-h symmetries, have been generated by using the semiempirical AM1 and PM3 methods, the density functional theory (DFT) B3LYP method with the 6-31 G(d) and LANL2DZ basis sets from the Gaussian 03 package, and the local density functional approximation (LDA), which is implemented in the SIESTA package. The calculated diameters for these Td symmetric hydrogenated silicon nanoclusters are in the range from 6.61 angstrom (Si5H12) to 23.24 angstrom (Si281H172). For the I-h symmetry, we calculated Si20H20 and Si100H60 nanoclusters only. Theoretically, the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is size dependent. The calculated energy gap decreases (Si5H12: 7.65 eV to Si281H172: 3.06 eV) while the diameter of silicon nanocluster increases. By comparing different calculated results, we concluded that the calculated energy gap by B3LYP/6-31G(d)//LDA/SIESTA is close to that from experiment and that the LDA/SIESTA result underestimates the experimental value. On the contrary, the AM I and PM3 results overestimate the experimental results. For investigation of the optical properties of Si nanoclusters as a function of surface passivation, we carried out a B3LYP/6-31G(d)//LDA/SIESTA calculation of the Si-35 and Si-47 core clusters with full alkyl-, OH-, NH2-, CH2NH2-, OCH3-, SH-, C3H6SH-, and CN- passivations. The calculated optical properties of alkyl passivated Si-35 nanoclusters (Si-35(CH3)(36), Si-35(C2H5)(36), and Si-35(C3H7)(36)) are close to one another and are higher than those of oxide, nitride, and sulfide passivated Si-35 clusters. In conclusion, the alkyl passivant affects weakly the calculated optical gaps, and the electron-withdrawing passivants-generate a red-shift in the energy gap of silicon nanoclusters. A size-dependent effect is also observed for these passivated Si nanoclusters.
Relation:	JOURNAL OF PHYSICAL CHEMISTRY A Volume: 112 Issue: 28 Pages: 6351-6357
Appears in Collections:	[Department of Physics ] journal articles

Files in This Item:

There are no files associated with this item.

Loading...