标题：Plasmonic nanoneedle arrays with enhanced hot electron photodetection for near-IR imaging

作者：Cheng Zhang ^a,b,*, Binglin Huang ^a,b, Haoyu Li ^a,b, Hui Chen ^a,b, Tong Yu ^a,b, Bingchang Zhang ^a,b,*, Shaojun Wang ^a,b,Changxu Liu^c, Yu Luo^d, Stefan A. Maier^e,f, and Xiaofeng Li ^a,b,*

单位：

^aSchool of Optoelectronic Science and Engineering & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China;

^bKey Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006, China;

^cCentre for Metamaterial Research & Innovation, Department of Engineering, University of Exeter, Exeter EX4 4QF, UK;

^dSchool of Electrical and Electronic Engineering,Nanyang Technological University,Nanyang Avenue, Singapore 639798, Singapore;

^eSchool of Physics and Astronomy Monash University Clayton Victoria 3800, Australia;

^fThe Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, UK;

摘要：Hot electron photodetection based on metallic nanostructures is attracting significant attention due to its potential to overcome the limitation of the traditional semiconductor bandgap. To enable efficient hot electron photodetection for practical applications, it is necessary to achieve broadband perfect light absorption and strong near-field enhancement simultaneously within extremely thin plasmonic nanostructures using cost-effective fabrication techniques. In this study, we demonstrate an ultra-high optical absorption (up to 97.3% in average across the spectral range of 1200−2400 nm) in the ultrathin plasmonic nanoneedle arrays (NNs) with thickness of 10 nm, based on a carefully designed all-wet metal-assisted chemical etching process. The significant absorption can be attributed to the combination of localized surface plasmons, propagating surface plasmons and waveguide modes. The resulting efficient hot electron generation, transport and injection at the nanoscale apex of the nanoneedles facilitates the photodetector to achieve a record low noise equivalent power (NEP) of 4.4  10⁻¹² W Hz^−0.5 at the wavelength of 1300 nm, to the best of our knowledge. We elucidate the hot-electron generation and injection process through a transport model based on a Monte Carlo approach, which quantitatively matches the experimental data. The measured external quantum efficiency is beyond the limit that can be achieved under a planar configuration with a film thickness of only 5 nm. We further integrate the photodetector into a light imaging system, as a demonstration of the exceptional imaging capabilities at the near-IR regime. The study presents a lithography-free, scalable, and cost-effective approach to enhance hot electron photodetection, with promising prospects for future imaging systems.

影响因子：19

链接：https://onlinelibrary.wiley.com/doi/full/10.1002/adfm.202304368