THz plasmonics and electronics in germanene nanostrips

Germanene nanostrips(GeNSs)have garnered significant attention in modern semiconductor technology due to their exceptional physical characteristics,positioning them as promising candidates for a wide range of applications.GeNSs exhibit a two-dimensional(buckled)honeycomb-like lattice,which is similar to germanene but with controllable bandgaps.The modeling of GeNSs is essential for developing appropriate synthesis methods as it enables understanding and controlling the growth process of these systems.Indeed,one can adjust the strip width,which in turn can tune the bandgap and plasmonic response of the material to meet specific device requirements.In this study,the objective is to investigate the electronic behav-ior and THz plasmon features of GeNSs(≥100 nm wide).A semi-analytical model based on the charge-carrier velocity of free-standing germanene is utilized for this purpose.The charge-carrier velocity of freestanding germanene is determined through the GW approximation(V_(F)=0.702×10^(6)m·s^(−1)).Within the width range of 100 to 500 nm,GeNSs exhibit narrow bandgaps,typi-cally measuring only a few meV.Specifically,upon analysis,it was found that the bandgaps of the investigated GeNSs ranged between 29 and 6 meV.As well,these nanostrips exhibit√q-like plasmon dispersions,with their connected plasmonic fre-quency(≤30 THz)capable of being manipulated by varying parameters such as strip width,excitation plasmon angle,and sam-ple quality.These manipulations can lead to frequency variations,either increasing or decreasing,as well as shifts towards larger momentum values.The outcomes of our study serve as a foundational motivation for future experiments,and further con-firmation is needed to validate the reported results.

Patterning graphene nanostripes in substrate-supported functionaUzed graphene： A promising route to integrated, robust, and superior transistors

It is promising to apply quantum-mechanically confined graphene systems in field-effect transistors. High stability, superior performance, and large-scale integration are the main challenges facing the practical application of graphene transistors. Our understandings of the adatom-graphene interac- tion combined with recent progress in the nanofabrication technology indicate that very stable and high-quality graphene nanostripes could be integrated in substrate-supported functionalized （hydro- genated or fluorinated） graphene using electron-beam lithography. We also propose that parallelizing a couple of graphene nanostripes in a transistor should be preferred for practical application, which is also very useful for transistors based on graphene nanoribbon.

Large-area flexible nanostripe electrodes featuring plasmon hybridization engineering

Multifunctional flexible Au electrodes based on one-dimensional(1D)arrays of plasmonic gratings are nanofabricated over large areas with an engineered variant of laser interference lithography optimized for low-cost transparent templates.Au nanostripe(NS)arrays achieve sheet resistance in the order of 20 Ohm/square on large areas(∼cm^(2))and are characterized by a strong and dichroic plasmonic response which can be easily tuned across the visible(VIS)to near-infrared(NIR)spectral range by tailoring their cross-sectional morphology.Stacking vertically a second nanostripe,separated by a nanometer scale dielectric gap,we form near-field coupled Au/SiO_(2)/Au dimers which feature hybridization of their localized plasmon resonances,strong local field-enhancements and a redshift of the resonance towards the NIR range.The possibility to combine excellent transport properties and optical transparency on the same plasmonic metasurface template is appealing in applications where low-energy photon management is mandatory like e.g.,in plasmon enhanced spectroscopies or in photon harvesting for ultrathin photovoltaic devices.The remarkable lateral order of the plasmonic NS gratings provides an additional degree of freedom for tailoring the optical response of the multifunctional electrodes via the excitation of surface lattice resonances,a Fano-like coupling between the broad localised plasmonic resonances and the collective sharp Rayleigh modes.