Active tunable terahertz bandwidth absorber based on single layer graphene

In this paper,an active tunable terahertz bandwidth absorber based on single-layer graphene is proposed,which consists of a graphene layer,a photo crystal plate,and a gold substrate.When the Fermi energy(Ef)of graphene is 1.5 eV,the absorber shows high absorption in the range of 3.7 THz–8 THz,and the total absorption rate is 96.8%.By exploring the absorption mechanism of the absorber,the absorber shows excellent physical regulation.The absorber also shows good adjustability by changing the Efof graphene.This means that the absorber exhibits excellent tunability by adjusting the physical parameters and Efof the absorber.Meanwhile,the absorber is polarization independent and insensitive to the incident angle.The fine characteristics of the absorber mean that the absorber has superior application value in many fields such as biotechnology and space exploration.

Plasmon-induced hot carrier dynamics and utilization

Plasmonics has aroused tremendous interest in photophysics,nanophotonics,and metamaterials.The extreme field concentration of plasmonics offers the ultimate spatial and temporal light control,single-particle detection,and optical modulation.Plasmon decay of metal nanostructures into hot carriers extends the application into photocatalysis,photodetectors,photovoltaics,and ultrafast nanooptics.The generated hot electron–hole pairs are transferred into adjacent dielectrics,well known to be more efficient than the hot carrier generation in dielectrics by direct photoexcitations.However,plasmon-induced hot-carrier-based devices are far from practical applications due to the low quantum yield of hot carrier extraction.Emergent challenges include low hot carrier generation efficiency in metals,rapid energy loss of hot carriers,and severe charge recombination at the metal/dielectric interface.In this review,we provide a fundamental insight into the hot carrier generation,transport,injection,and diffusion into dielectrics based on the steady-state and time-resolved spectroscopic studies as well as theoretical calculations.Strategies to enhance hot carrier generation in metals and electron transfer into dielectrics are discussed in detail.Then,applications based on hot carrier transfer are introduced briefly.Finally,we provide our suggestions on future research endeavors.We believe this review will provide a valuable overall physical picture of plasmon-induced hot carrier applications for researchers.

Alkali-metal(Li, Na, and K)-adsorbed MoSi_(2)N_(4) monolayer: an investigation of its outstanding electronic, optical, and photocatalytic properties

Single-layer MoSi_(2)N_(4),a high-quality two-dimensional material,has recently been fabricated by chemical vapor deposition.Motivated by this latest experimental work,herein,we apply first principles calculations to investigate the electronic,optical,and photocatalytic properties of alkali-metal(Li,Na,and K)-adsorbed MoSi_(2)N_(4) monolayer.The electronic structure analysis shows that pristine MoSi_(2)N_(4) monolayer exhibits an indirect bandgap(E_(g)=1.89 eV).By contrast,the bandgaps of one Li-,Na-,and K-adsorbed MoSi_(2)N_(4) monolayer are 1.73 eV,1.61 eV,and 1.75 eV,respectively.Moreover,the work function of MoSi_(2)N_(4) monolayer(4.80 eV)is significantly reduced after the adsorption of alkali metal atoms.The work functions of one Li-,Na-,and K-adsorbed MoSi_(2)N_(4) monolayer are 1.50 eV,1.43 eV,and 2.03 eV,respectively.Then,optical investigations indicate that alkali metal adsorption processes substantially increase the visible light absorption range and coefficient of MoSi_(2)N_(4) monolayer.Furthermore,based on redox potential variations after alkali metals are adsorbed,Li-and Na-adsorbed MoSi_(2)N_(4) monolayers are more suitable for the water splitting photocatalytic process,and the Li-adsorbed case shows the highest potential application for CO_(2) reduction.In conclusion,alkali-metal-adsorbed MoSi_(2)N_(4) monolayer exhibits promising applications as novel optoelectronic devices and photocatalytic materials due to its unique physical and chemical properties.