Fundamental dynamic processes at the electronic contact interface, such as carrier injection and transport, become pivotal and significantly affect device performance. Time-resolved photoemission electron microscopy (TR-PEEM) with high spatiotemporal resolution provides unprecedented abilities of imaging the electron dynamics at the interface. Here, we implement TR-PEEM to investigate the electron dynamics at a coplanar metallic 1T′-MoTe2/semiconducting 2H-MoTe2 heterojunction. We find the non-equilibrium electrons in the 1 T′-MoTe2 possess higher energy than those in the 2H-MoTe2. The nonequilibrium photoelectrons collapse and relax to the lower energy levels in the order of picoseconds. The photoexcited electrons transfer from 1 T′-MoTe2 to 2H-MoTe2 with at a rate of ~0.8 × 1012 s−1 (as fast as 1.25 ps). These findings contribute to our understanding of the behavior of photoexcited electrons in heterojunctions and the design of in-plane optoelectronic devices.
We investigated in situ the interaction between a single gold nanorod and monolayer transition metal dichalcogenides (TMDCs) by atomic force microscopy nanomanipulation and single-particle spectroscopy.We observed that the resonant scattering peak of the hybrid redshifted, the full width at half maximum of the scattering resonance narrowed and the scattering intensity increased compared with those of the same nanorod before coupling with monolayer TMDCs. These results were understood with the aid of finite-difference time-domain simulations, the Fano model, and the classical oscillator model. Also, the spectral features varied with the distance between the nanorod and TMDCs, and the interaction was mainly attributed to the resonant energy transfer effect. Our findings clarify the influence of TMDCs on the plasmonic resonance and contribute to a deeper understanding of the plasmon exciton interaction.
We investigated in situ the coupling spectra of a single gold nanorod and monolayer transition metal dichalcogenides (TMDCs) using nanomanipulation technique and single-particle spectroscopy. The resonant scattering peak of the hybrid redshifted, the full width at half maximum of the resonance narrowed, and the scattering intensity increased compared with those of the same nanorod on the glass surface, i.e., before coupling with monolayer TMDCs. Also, the spectral features varied with the distance between the nanorod and TMDCs, and the coupling interaction should be dominated mainly by the resonant energy transfer effect rather than the electron transfer process.
In experiments, we demonstrated that luminescence quantum yield of single gold nanorods illuminated by continuous wave laser at wavelength of 532 nm depends on the excitation polarization, while that excited by 633 nm laser does not. The electrons in sp-band dominates the luminescence process when the 633 nm laser is applied, resulting in a constant quantum yield under different excitation polarizations. When the 532 nm laser is applied, both the electrons in d-band (interband transition) and sp-band (surface plasmon) involve in the luminescence process. The variation of quantum yield by the 532 nm laser is resulted from different efficiency of d-band interband transition and sp-band plasmon conversion into luminescence. Furthermore, we found that plasmon modes coupling effect can modulate strongly the plasmon emission efficiency by comparing the luminescence of two sets of the nanorods with different size. And smaller size GNRs often results in higher quantum yield of interband transition. These findings make a step to understand the luminescence process of plasmonic nanostructures and point out a rule to control it through plasmon mode coupling effect.
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