Fig. 1. Fundamental and characteristic of surface plasmons. (a) Schematic of surface plasmon polaritons at metal-dielectric interface[21]; (b) schematic of localized surface plasmon resonance in metal nanosphere[21]; (c) extinction spectra of localized surface plasmons of noble metals and doped semiconductor materials[24]

Fig. 2. Photoexcitation and relaxation of metallic nanoparticles[29]. (a) Distribution of electromagnetic field under excitation of localized surface plasmon resonance; (b) non-thermal equilibrium distribution of electron-hole pairs (Landau damping occurs within 1-100 fs); (c) hot carriers will redistribute their energy by electron-electron scattering process; (d) heat is transferred to the surroundings of the metallic structure via thermal conduction

Fig. 3. Charge transfer process at the interface of metal and semiconductor[30]. (a) Conventional surface plasmon-induced hot-electron transfer process; (b) surface plasmon-induced charge-transfer transition process; (c) surface plasmon-induced resonant energy transfer process

Fig. 4. Quantification of hot electron injection efficiency. (a) Schematic of structure, hot electron transfer, and wavelength-dependent photoresponsivity of hot-electron based Au-Si Schottky photo detector[37]; (b) hot electron transfer based photoelectric conversion in Au-GaN heterostructure (left), distribution of hot electrons under excitation with photon energy of 1.4 eV and 2.4 eV (top right), and external quantum efficiency of device as a function of incident photon energy (bottom right)[38]

Fig. 5. Infrared photodetectors based on low dimensional materials. (a) Structure of Ti2O3-graphene infrared photoconductor and photoelectric response under different light wavelengths[4]; (b) diagram of InAs nanowire photodetector and output characteristics under different illumination wavelengths[46]; (c) photovoltaic infrared detector based on MoS2-graphene-WSe2 heterostructure and photoelectric response at different wavelengths[47]

Fig. 6. Infrared detection based on plasmon-induced hot electrons in noble metals. (a) Schematic of gold heptamer-graphene device, position-dependent photocurrent, and contribution of different mechanisms to photocurrent[52]; (b) schematic of grating-based Schottky junction detector and photocurrent responsivities of grating-based photodetectors with different gold layer thicknesses[53]; (c) schematic of MoS2 photodetector with asymmetric metal electrodes, and photoresponse and energy band under differe

Fig. 7. Photodetection based on doped plasmonic semiconductors. (a) Plasmon-induced hot-hole transfer in the system of CdS/CuS nanocrystal heterostructure[51]; (b) schematic of the device,the photoelectric conversion at ITO/SnO2 heterostructure (left), and photoresponse of the device at infrared region (right)[57]; (c) schematic of the structure (left) and charge transfer (middle) of the hybrid phototransistor based on B-doped Si quantum dots and graphene. Responsivity at different wavelengths (right)[9