Giant Negative Terahertz Photoconductivity in Controllably Doped Carbon Nanotube Networks
Giant Negative Terahertz Photoconductivity in Controllably Doped Carbon Nanotube Networks
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DOI：
10.1021/acsphotonics.9b00138
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发表时间：
2019-04-01
期刊：
影响因子：
7
通讯作者：
Lloyd-Hughes, James
中科院分区：
文献类型：
--
作者：
Burdanova, Maria G.;Tsapenko, Alexey P.;Lloyd-Hughes, James
利用光泵浦、太赫兹探测光谱等手段，在单壁碳纳米管薄膜网络中发现了较强的负光电导。薄膜的掺杂是可控的，要么使用不同p型掺杂浓度的吸附掺杂，要么使用离子栅双极掺杂。掺杂提高了太赫兹电导率，增加了动量散射率，带间光激发降低了光谱重量，降低了动量散射率。无论化学势如何，在所有掺杂水平下都观察到了这种负的太赫兹光电导性，并在几皮秒内衰减。这些一维导体固有的强多体相互作用导致在光激发下形成三子，从而降低了碳纳米管网络的整体电导率。太赫兹负光电导的大幅度和恢复时间随掺杂的可调性为包括太赫兹探测器、偏振器和调制器在内的光谱宽带超快器件提供了希望。
A strong negative photoconductivity was identified in thin film networks of single-walled carbon nanotubes using optical pump, THz probe spectroscopy. The films were controllably doped, using either adsorption doping with different p-type dopant concentrations or ambipolar doping using an ionic gate. While doping enhanced the THz conductivity and increased the momentum scattering rate, interband photoexcitation lowered the spectral weight and reduced the momentum scattering rate. This negative THz photoconductivity was observed for all doping levels, regardless of the chemical potential, and decayed within a few picoseconds. The strong many-body interactions inherent to these 1D conductors led to trion formation under photoexcitation, lowering the overall conductivity of the carbon nanotube network. The large amplitude of negative THz photoconductivity and the tunability of its recovery time with doping offer promise for spectrally wide-band ultrafast devices, including THz detectors, polarizers, and modulators.