They also observed a centrally located large plasmon hotspot in each domain, suggesting that the high-density GB regions are the origin of hotspots.Ī nano-Fourier transform infrared (nano-FTIR) spectrum, which was collected from the SNOM tip around the hotspot, was used to demonstrate the local fingerprint spectroscopy. Based on the dark-field TEM and growth mechanism observations, the team confirmed the formation of high-density GBs inside the hole at the center of the individual graphene domain. The plasmons in inhomogenous PG (IPG) film was studied using SNOM, under an incident infrared (IR) wavelength of approximately 10 micrometers. The film showed highly crystalline areas with similar morphologies and variation in GB density. The fast Fourier transformation pattern revealed differently oriented grains in multiple numbers. The high-resolution TEM characterization with aberration-correction showed that the polycrystalline graphene (PG) rings contained graphene grains devoid of defects and tethered at GBs with pentagons and heptagons. The grain sizes obtained for the outer, ring, and inner area were 140 ± 56, 40 ± 21, and 30 ± 13 nanometers, respectively. The dark-field TEM image showed that the ring area had a gradient grain size structure and on approaching the ring center, the GB density increased. The graphene grain structure’s whole maps were created and were color-coded by a lattice orientation. The researchers obtained a real-space image of grain in a selected orientation via an objective aperture filter. The SAED pattern showed many families of spots that indicated the presence of many differently oriented grains. The graphene film ring area’s grain structure was investigated by employing selected-area electron diffraction (SAED) and transmission electron microscopy (TEM). Furthermore, the GB-based controllable plasmon co-generation and manipulation in a single graphene monolayer facilitates the use of graphene for nanophotonics and plasmonics. The reported seed-induced heteroepitaxial growth is a promising strategy for GB engineering of 2D materials. Based on theoretical modeling, they inferred that reason for such plasmonic versatility was due to GB-induced phonon-plasmon interactions via the random phase approximation method. They observed that the local plasmonic wavelengths were tunable by annealing and varying the GB density. The team demonstrated the rich plasmon standing waves and bright plasmonic hotspots using high-resolution scanning nearfield optical microscopy (SNOM). Using Graphene Based Solar Cells for Solar Applications.These geometries enabled plasmonic co-excitation with the diversification of wavelengths. They employed the chemical vapor deposition method to create various nanosized local growth environments on a substrate of a centimeter scale. The present study reported the heteroepitaxially grown polycrystalline graphene monolayer with patterned gradient GB density. Graphene GBs for Plasmonic Multi-excitation and Hotspots Several strategies have been developed to reduce and increase GB density these strategies were limited to creating growth environments that are homogeneous over the entire substrate, which restricts the diverse GB generation. Thus, the application and influence of GBs on plasmonic modes remains elusive. In addition to microfabrication nanostructuring and chemical potential modulation, graphene’s GB serves as a promising candidate to obstruct or reflect the plasmons in real space.ĭespite the efficiency of GBs in reconstructing the graphene structure, which facilitates the tuning of graphene plasmonics, it suffers from extreme impurity doping and high-density issues, hindering it from achieving a single graphene monolayer with diverse and dense GB. The graphene plasmons have excellent electromagnetic controllability and confinement that dominate far-infrared and terahertz frequencies. Graphene’s two-dimensionally (2D) correlated quasiparticles that can oscillate collectively make an interdisciplinary field in graphene plasmonics. Image Credit: Marco de Benedictis/ Graphene GBs Study: Engineering Graphene Grain Boundaries for Plasmonic Multi-Excitation and Hotspots. In an article recently published in the journal ACS Nano, the researchers reported heteroepitaxially grown polycrystalline graphene monolayer with patterned gradient grain boundary (GB) density to aid the development of single atomic layer nanoscience, integrated photonics, and optoelectronics. By Bhavna Kaveti Reviewed by Susha Cheriyedath, M.Sc.Īlthough graphene offers tremendous advantages for plasmon technologies, it is often difficult to co-excite multiple graphene plasmons on a highly dense single graphene sheet.
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