Wavelength-Dependent Absorption in Structurally Tailored Randomly Branched Vertical Arrays of InSb Nanowires
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- 作者：Asaduzzaman Mohammad ; Suprem R. Das ; M. Ryyan Khan ; Muhammad A. Alam ; David B. Janes
- 刊名：Nano Letters
- 出版年：2012
- 出版时间：December 12, 2012
- 年：2012
- 卷：12
- 期：12
- 页码：6112-6118
- 全文大小：356K
- 年卷期：v.12,no.12(December 12, 2012)
- ISSN：1530-6992
文摘
Arrays of semiconductor nanowires are of potential interest for applications including photovoltaic devices and IR detectors/imagers. While nominally uniform arrays have typically been studied, arrays containing nanowires with multiple diameters and/or random distributions of diameters could allow tailoring of the photonic properties of the arrays. In this Letter, we demonstrate the growth and optical properties of randomly branched InSb nanowire arrays. The structure mentioned can be approximated as three vertically stacked regions, with average diameters of 20, 100, and 150 nm within the respective layers. Reflectance and transmittance measurements on structures with different average nanowire lengths have been performed over the wavelength range of 300鈥?000 nm, and absorbance has been calculated from these measurements. The structures show low reflectance over the visible and IR regions and wavelength-dependent absorbance in the IR region. A model considering the diameter-dependent photonic coupling (at a given wavelength) and random distribution of nanowire diameters within the regions has been developed. The diameter-dependent photonic coupling results in a roll-off in the absorbance spectra at wavelengths well below the bulk cutoff of 7 渭m, and randomness is observed to broaden the absorbance response. Varying the average diameters would allow tailoring of the wavelength dependent absorption within various layers, which could be employed in photovoltaic devices or wavelength-dependent IR imagers.