入射角度和偏振对锥形硅纳米线光谱行为的影响

doi:10.3964/j.issn.1000-0593(2020)11-3394-05

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Abstract The extinction section of a silicon nanowire can reach hundreds of times its geometric cross-sectional area at a given wavelength, meaning it can collect light in the area a scope hundreds of times of its geometrical cross-sectional area. Therefore, silicon nanowire has been widely used in many optoelectronic fields like solar cells, sensors, and photocatalysis devices. Cylindrical silicon nanowire (C-SiNW) and tapered silicon nanowire (T-SiNW) are the two most important silicon nanowire structures. Between them, the extinction efficioncy of T-SiNW has a wider waveband with a large extinction efficiency, so it shows better ability to collect broad-spectrum light. Nevertheless, when under top irradiation, the absorption efficioncy of T-SiNW is quite small, which severely limits its practical applications. It is urgent to find out the law that the incident angle affects the spectral behaviors of T-SiNW. Besides, the polarization of incident light will also influence the spectral behaviors of T-SiNW. In this work, the influence of angle and polarization of incident light on the extinction, absorption spectra and scattering properties of T-SiNW was carefully studied, using the discrete dipole approximation method. T-SiNW was modeled with the length of 1 μm, top-diameter of 20 nm, and bottom-diameter of 120 nm; the angle of incident light increases from 0° to 180° with an interval of 30 °; and two polarization states, parallel and vertical to the incident plane, were considered. First, impacts of the incident angle and polarization on the extinction, absorption spectra, and the ratio of the absorbed light (Abs./Ext.) of T-SiNW were studied. Meanwhile, the mechanisms for the spectral behaviors of T-SiNW were discussed by means of analyzing the near-field distribution mappings. Then, the influence of the angle and polarization on the scattering angle distribution of T-SiNW was analyzed. The results show that the fully inverted T-SiNW has the same extinction spectrum as the upright one, but its absorption spectrum increases significantly: the average Abs./Ext. ratio exceeds 70% in waveband ranging from 0.3 to 0.55 μm. The horizontally placed T-SiNW has the largest extinction spectral value and the smallest absorption spectral value, so it shows the strongest light collection ability whereas the smallest light absorption ratio. Meanwhile, it can scatter the vertical incident light in approximate horizontal directions. In addition, T-SiNW shows larger absorption spectral values for parallel-polarized light than vertical-polarized light, but smaller Abs./Ext. ratio.

Key words：Tapered silicon nanowire; Spectral behavior; Angle of incident light; Polarization

Received: 2019-10-28 Accepted: 2020-02-20

ZTFLH:

O436.2

Corresponding Authors: LI Ying-feng E-mail: liyingfeng@ncepu.edu.cn

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)11-3394-05 OR https://www.gpxygpfx.com/EN/Y2020/V40/I11/3394