This study investigates recent advances in photoelectron emission generated by irradiating ultrashort lasers on metallic nanostructures and low-dimensional carbon materials. Recently, primary focus has been on improving the efficiency of emitters, i.e. increasing the number of field-emitted electrons and their respective kinetic energies. An example of this is the modification of the conventional metal nanotip through adiabatic nanofocusing and various plasmonic metal structures, such as nanorods and bowtie antenna. The coherent emission control with two color irradiation enabled modulation in the emission yield. In addition, THz waves near the metallic nanostructure induced a highly accelerated, monochromatic energy. Alternative to metallic nanotips, carbon nanotubes are emerging as efficient photoelectron emitters, due to the large enhancement factor associated with their high aspect ratio and damage threshold. They particularly allowed the use of femtosecond light sources with a relatively short wavelength, resulting in the generation of photoelectrons with a narrow bandwidth. Additionally, electronic control over the single-walled nanotubes band structure added a degree of freedom for controlling the electron emission yield. Finally, we review the strong-field tunneling emission in graphene edge, with the emission yield showing an anomalous increase of nonlinear order, corresponding to the deep strong tunneling regime.

Research on surface plasmon resonance coupling of metallic nanostructures is an important area in the field of plasmonics because distinctive collective optical properties can be realized that are different from the individual constituents. Here we report the localized surface plasmon resonance of hybrid metal-organic nanorods. Colloidal-dispersed Au-PPy nanorods were synthesized as a representative material using a modified electrochemical method, and the collective oscillation properties were systematically investigated by comparing these materials with pure Au nanorods. We observed the extended surface plasmon resonance of a hybrid system. The presence of doped-PPy segments on Au segments induced an enhanced coherent electric field due to the partial contribution of π-electrons on the PPy segment, which led to a red-shifted plasmon feature. Additionally, we demonstrated that surface plasmon resonance extension can be tuned by dopant anions, which demonstrates a way of tuning a dopant-induced plasmonic system.

Modulation of the carrier concentration and electronic type of monolayer (1L) MoS₂ is highly important for applications in logic circuits, solar cells, and light-emitting diodes. Here, we demonstrate the tuning of the electronic properties of large-area 1L-MoS₂ using graphene oxide (GO). GO sheets are well-known as hole injection layers since they contain electron-withdrawing groups such as carboxyl, hydroxyl, and epoxy. The optical and electronic properties of GO-treated 1L-MoS₂ are dramatically changed. The photoluminescence intensity of GO-treated 1L-MoS₂ is increases by more than 470% compared to the pristine sample because of the increase in neutral exciton contribution. In addition, the A_1g peak in Raman spectra shifts considerably, revealing that GO treatment led to the formation of p-type doped 1L-MoS₂. Moreover, the current vs voltage (I-V) curves of GO-coated 1L-MoS₂ field effect transistors show that the electron concentration of 1L-MoS₂ is significantly lower in comparison with pristine 1L-MoS₂. Current rectification is also observed from the I-V curve of the lateral diode structure with 1L-MoS₂ and 1L-MoS₂/GO, indicating that the electronic structure of MoS₂ is significantly modulated by the electron-withdrawing functional group of GO.

This study investigates recent advances in photoelectron emission generated by irradiating ultrashort lasers on metallic nanostructures and low-dimensional carbon materials. Recently, primary focus has been on improving the efficiency of emitters, i.e. increasing the number of field-emitted electrons and their respective kinetic energies. An example of this is the modification of the conventional metal nanotip through adiabatic nanofocusing and various plasmonic metal structures, such as nanorods and bowtie antenna. The coherent emission control with two color irradiation enabled modulation in the emission yield. In addition, THz waves near the metallic nanostructure induced a highly accelerated, monochromatic energy. Alternative to metallic nanotips, carbon nanotubes are emerging as efficient photoelectron emitters, due to the large enhancement factor associated with their high aspect ratio and damage threshold. They particularly allowed the use of femtosecond light sources with a relatively short wavelength, resulting in the generation of photoelectrons with a narrow bandwidth. Additionally, electronic control over the single-walled nanotubes band structure added a degree of freedom for controlling the electron emission yield. Finally, we review the strong-field tunneling emission in graphene edge, with the emission yield showing an anomalous increase of nonlinear order, corresponding to the deep strong tunneling regime.

Research on surface plasmon resonance coupling of metallic nanostructures is an important area in the field of plasmonics because distinctive collective optical properties can be realized that are different from the individual constituents. Here we report the localized surface plasmon resonance of hybrid metal-organic nanorods. Colloidal-dispersed Au-PPy nanorods were synthesized as a representative material using a modified electrochemical method, and the collective oscillation properties were systematically investigated by comparing these materials with pure Au nanorods. We observed the extended surface plasmon resonance of a hybrid system. The presence of doped-PPy segments on Au segments induced an enhanced coherent electric field due to the partial contribution of π-electrons on the PPy segment, which led to a red-shifted plasmon feature. Additionally, we demonstrated that surface plasmon resonance extension can be tuned by dopant anions, which demonstrates a way of tuning a dopant-induced plasmonic system.

Modulation of the carrier concentration and electronic type of monolayer (1L) MoS₂ is highly important for applications in logic circuits, solar cells, and light-emitting diodes. Here, we demonstrate the tuning of the electronic properties of large-area 1L-MoS₂ using graphene oxide (GO). GO sheets are well-known as hole injection layers since they contain electron-withdrawing groups such as carboxyl, hydroxyl, and epoxy. The optical and electronic properties of GO-treated 1L-MoS₂ are dramatically changed. The photoluminescence intensity of GO-treated 1L-MoS₂ is increases by more than 470% compared to the pristine sample because of the increase in neutral exciton contribution. In addition, the A_1g peak in Raman spectra shifts considerably, revealing that GO treatment led to the formation of p-type doped 1L-MoS₂. Moreover, the current vs voltage (I-V) curves of GO-coated 1L-MoS₂ field effect transistors show that the electron concentration of 1L-MoS₂ is significantly lower in comparison with pristine 1L-MoS₂. Current rectification is also observed from the I-V curve of the lateral diode structure with 1L-MoS₂ and 1L-MoS₂/GO, indicating that the electronic structure of MoS₂ is significantly modulated by the electron-withdrawing functional group of GO.

We present a method that uses viscosity-lowering materials to fabricate flexible polydimethylsiloxane-based quantum dot (QD) films with high quantum yield (QY) and improved uniformity. We found that the aggregation of individual QDs was prevented, and the QY improved simultaneously in films that contained surfactants. These films showed an improved absorption of approximately 27% in the near-UV and blue light regions, along with an improved photoluminescence of approximately 18%, indicating improved light conversion from the UV to the visible frequency region.

We theoretically demonstrates large field enhancement at the close-packed, truncated octahedral gold nanoparticle array by using a finite difference time domain method. A multiple peak at the visible and near infrared frequency implies the multiple resonance in the nanostructures, corresponding to the dipolar and quadrupolar mode excitation of electric field at the single octahedral particles. The splitting of two adjacent resonant peak as a function of the distance of the particles implies the existence of the significant coupling between the resonant modes of the individual nanoparticles. The electric field profile at the gap between the particles shows the field enhancement due to such mode couplings, where dipolar and quadrupolar mode are simultaneously involved. Such evolution of mode coupling with increasing gap distance confirms the resonant modes excitation and their coupling is the origin of the strong field enhancement. Simulation with different polarization of the incident light denotes the dominant coupling mode is governed by the size of the interaction area. Importantly, electric field at the gap is hugely enhanced up to 17 at the optimal gap distance of 4 nm.