Optical Properties of Doped Silicon Quantum Dots with Crystalline and Amorphous Structures

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• 作者：Michael G. Mavros ; David A. Micha ; Dmitri S. Kilin
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：October 13, 2011
• 年：2011
• 卷：115
• 期：40
• 页码：19529-19537
• 全文大小：1020K
• 年卷期：v.115,no.40(October 13, 2011)
• ISSN：1932-7455

文摘

The interaction of silicon quantum dots with light is remarkable, as electronic transitions are influenced by the interplay of their atomic structure and by electronic quantum confinement in three dimensions. In this study, the optical properties of 4 undoped and 16 doped silicon quantum dots were calculated using time-dependent density functional theory. The HOMO鈥揕UMO gap, maximum absorption wavelength, and oscillator strength at that wavelength were calculated for two crystalline structures, c-Si₂₉H₃₆ and c-Si₃₅H₃₆, and two amorphous structures, a-Si₂₉H₃₆ and a-Si₃₅H₃₆; in addition, optical properties were calculated for each of the structures doped with either phosphorus or aluminum in one of two different positions: in the center of the cluster or at the surface of the cluster. The calculated optical properties reveal that the absorbance spectrum of the amorphous structures is red shifted compared to that of the crystalline structures, and doping causes the spectrum to shift even further toward the red. Additionally, absorption of light at the maximum wavelength in doped structures caused charge density to transfer from the center of the quantum dot to the surface. The combination of strong absorptions in the visible region of the electromagnetic spectrum and the observed charge transfer make doped silicon quantum dots promising candidates as materials for solar energy applications.