Department of Electrical and Computer Engineering, ‡Waterloo Institute of Nanotechnology, and §Department of Physics and Astronomy, University of Waterloo , 200 University Ave West, Waterloo, ON N2L 3G1, Canada.
Nano Lett. 2014 Oct 8;14(10):5820-6. doi: 10.1021/nl5026979. Epub 2014 Sep 23.
The photothermal properties of vertically etched gallium arsenide nanowire arrays are examined using Raman spectroscopy. The nanowires are arranged in square lattices with a constant pitch of 400 nm and diameters ranging from 50 to 155 nm. The arrays were illuminated using a 532 nm laser with an incident energy density of 10 W/mm(2). Nanowire temperatures were highly dependent on the nanowire diameter and were determined by measuring the spectral red-shift for both TO and LO phonons. The highest temperatures were observed for 95 nm diameter nanowires, whose top facets and sidewalls heated up to 600 and 440 K, respectively, and decreased significantly for the smaller or larger diameters studied. The diameter-dependent heating is explained by resonant coupling of the incident laser light into optical modes of the nanowires, resulting in increased absorption. Photothermal activity in a given nanowire diameter can be optimized by proper wavelength selection, as confirmed using computer simulations. This demonstrates that the photothermal properties of GaAs nanowires can be enhanced and tuned by using a photonic lattice structure and that smaller nanowire diameters are not necessarily better to achieve efficient photothermal conversion. The diameter and wavelength dependence of the optical coupling could allow for localized temperature gradients by creating arrays which consist of different diameters.
使用拉曼光谱研究了垂直刻蚀砷化镓纳米线阵列的光热性能。纳米线以 400nm 的恒定间距排列，直径范围从 50nm 到 155nm。使用 532nm 激光照射，入射能量密度为 10W/mm(2)。纳米线的温度高度依赖于纳米线的直径，并通过测量 TO 和 LO 声子的光谱红移来确定。在 95nm 直径的纳米线中观察到最高的温度，其顶部和侧壁分别加热到 600K 和 440K，而研究的较小或较大直径的纳米线的温度则显著降低。直径依赖性加热是通过将入射激光光与纳米线的光学模式共振耦合来解释的，从而导致吸收增加。通过计算机模拟证实，通过适当的波长选择，可以优化给定纳米线直径的光热活性。这表明可以通过使用光子晶格结构来增强和调整 GaAs 纳米线的光热性质，并且较小的纳米线直径不一定能够实现高效的光热转换。光学耦合的直径和波长依赖性可以通过创建由不同直径组成的阵列来产生局部温度梯度。
