Large-area grain-boundary-free copper films for plasmonics

Chew, Soo Hoon; Gliserin, Alexander; Choi, Sungho; Geng, Xiao; Kim, Sujae; Hwang, Woonbong; Baek, Kangkyun; Anh, Nguyen Dong; Kim, Young‐Jin; Song, Young Min; Kim, Dong Eon; Jeong, Se–Young; Kim, Seungchul

doi:10.1016/j.apsusc.2020.146377

Cited by 12 publications

(9 citation statements)

References 68 publications

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“…Previous works have demonstrated that crystalline properties and surface morphologies of Ag films and nanostructures play an important role in plasmonic applications. − Especially, uniform and controllable plasmonic hotspots can be realized by high-fidelity top-down nanofabrication on ultrasmooth, single-crystalline Ag colloidal crystals. , In addition to epitaxial Ag films, ,− other plasmonic materials, such as Au, − copper (Cu), − titanium nitride (TiN), − and Al − films grown on miscellaneous substrates have been successfully developed for plasmonic applications − ,− ,− and 2D material growth templates. , The epitaxial growth approach offers many distinctive advantages for plasmonic applications, such as formation of large-area (wafer scale), low-loss (single crystalline), and ultrathin ( e . g ., tunable through gating and quantum optical effects) metal layers for top-down plasmonic device fabrication.…”

Section: Resultsmentioning

confidence: 99%

Epitaxial Aluminum Surface-Enhanced Raman Spectroscopy Substrates for Large-Scale 2D Material Characterization

et al. 2020

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Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive technique to identify vibrational fingerprints of trace analytes. However, present SERS techniques suffer from the lack of uniform, reproducible, and stable substrates to control the plasmonic hotspots in a wide spectral range. Here, we report the promising application of epitaxial aluminum films as a scalable plasmonic platform for SERS applications. To assess the uniformity of aluminum substrates, atomically thin transition metal dichalcogenide monolayers are used as the benchmark analyte due to their inherent two-dimensional homogeneity. Besides the distinctive spectral capability of aluminum in the ultraviolet (325 nm), we demonstrate that the aluminum substrates can even perform comparably with the silver counterparts made from single-crystalline colloidal silver crystals using the same SERS substrate design in the visible range (532 nm). This is unexpected from the prediction solely based on optical dielectric functions and illustrate the superior surface and interface properties of epitaxial aluminum SERS substrates.

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Section: Resultsmentioning

confidence: 99%

Epitaxial Aluminum Surface-Enhanced Raman Spectroscopy Substrates for Large-Scale 2D Material Characterization

et al. 2020

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“…Cu, however, is also a CMOS-compatible plasmonic material, widely used in microelectronic devices owing to its high electrical conductivity and natural abundance, and it can offer good plasmonic performance. ,− Recently, significant efforts have been made to explore Cu-based plasmonic applications, such as Cu plasmonic sub-wavelength waveguides, , hot carrier injection, biosensing, and infrared-blocking glass . However, the development of Cu plasmonic applications has been limited because of the lack of high-quality Cu films and its fast surface oxidation without a passivation layer …”

Section: Results and Discusionmentioning

confidence: 99%

“…In plasmonic applications, the performance limitations of plasmonic devices are determined by the properties of plasmonic materials. Gold and silver are currently the most commonly used plasmonic materials because of their excellent optical properties in the visible and near-infrared spectral regions. − However, the realization of widespread plasmonic applications requires additional material advantages, such as low cost, material stability, device scalability, broad spectral tunability, and possible device integration with complementary metal oxide semiconductor (CMOS) technologies. − Also, the surface morphology and crystalline quality of plasmonic materials are critical factors to fabricate efficient and reliable plasmonic devices. − For example, it has been demonstrated that the presence of crystalline defects and surface roughness can lead to strong optical losses and poor plasmonic device performance. Eventually, these imperfections prevent precise (high fidelity) and reproducible fabrication of plasmonic nanostructures, thus limiting their practical applications. , …”

Section: Introductionmentioning

confidence: 99%

Flexible Plasmonics Using Aluminum and Copper Epitaxial Films on Mica

et al. 2022

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We demonstrate here the growth of aluminum (Al), copper (Cu), gold (Au), and silver (Ag) epitaxial films on twodimensional, layered muscovite mica (Mica) substrates via van der Waals (vdW) heteroepitaxy with controllable film thicknesses from a few to hundreds of nanometers. In this approach, the mica thin sheet acts as a flexible and transparent substrate for vdW heteroepitaxy, which allows for large-area formation of atomically smooth, single-crystalline, and ultrathin plasmonic metals without the issue of film dewetting. The highquality plasmonic metal films grown on mica enable us to design and fabricate well-controlled Al and Cu plasmonic nanostructures with tunable surface plasmon resonances ranging from visible to the nearinfrared spectral region. Using these films, two kinds of plasmonic device applications are reported, including (1) plasmonic sensors with high effective index sensitivities based on surface plasmon interferometers fabricated on the Al/Mica film and (2) Cu/Mica nanoslit arrays for plasmonic color filters in the visible and near-infrared regions. Furthermore, we show that the responses of plasmonic nanostructures fabricated on the Mica substrates remain unaltered under large substrate bending conditions. Therefore, the metal-on-mica vdW heteroepitaxy platform is suitable for flexible plasmonics based on their bendable properties.

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“…Traditionally noble metals (silver, gold, and copper) are well-known plasmonic materials that exhibit SP resonances at optical frequencies. , Alternative materials like Al, Si, Ge, GaAs, InP, doped ZnO, and ITO have been used to excite plasmons in various spectral ranges. − Recall that the plasmon resonance can be controlled by tuning the dielectric permittivity (ε) of materials. In these materials, the ε is tuned by controlling the grain size and the surface roughness of the structures. − Recently, noble metal alloys have drawn attention as suitable plasmonic materials in the visible range because of an additional handle of composition which can be used to tune the permittivity . The advantage of alloying is that one can overcome the limitation of the fixed ε of metals at a given wavelength.…”

Section: Introductionmentioning

confidence: 99%

Microstructure Dictates the Behavior of Plasmons in Nanostructured Ag-Cu Alloy Films

et al. 2022

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Surface plasmon (SP) resonances play a vital role in the efficient control of light−matter interaction at the nanoscale beyond the diffraction limit. Alloy plasmonics has opened new avenues for composition-dependent tuning of the plasmonic response. In this study, we demonstrate that phase separation in immiscible alloy systems can be used as an additional degree of freedom in conjunction with the composition to tune the plasmon behavior. The Ag-Cu alloy system is used as a model case to demonstrate the implications of phase separation and composition on both propagating and localized SPs. We use magnetron cosputtering to deposit a metastable FCC solid solution thin film with nanocrystalline grains. Subsequent annealing of the film at 400 °C leads to phase separation and grain growth. The annealed samples exhibit Ag-rich and Cu-rich phases with composition-dependent connectivity. Dispersion of propagating SPs in thin films shows a significant dependence on the composition and annealing conditions. Annealing of the alloy films leads to a strong decrease, by a factor of up to 20%, in the resonance widths of the propagating SPs which is due to a decrease in the imaginary part of the permittivity. Nanoapertures fabricated using focused ion beam (FIB) milling show strong scattering signatures for the metastable and annealed samples. Finally, we demonstrate the site-specific fabrication of nanoapertures in the Cu or Ag domains using ionsecondary electron imaging in FIB. The proposed approach for realizing complex bimetallic nanostructures can potentially be used for realizing multiplexed metasurfaces, active plasmonic platforms, plasmon enhanced catalysis, and site-specific multianalyte sensing.

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Large-area grain-boundary-free copper films for plasmonics

Cited by 12 publications

References 68 publications

Epitaxial Aluminum Surface-Enhanced Raman Spectroscopy Substrates for Large-Scale 2D Material Characterization

Epitaxial Aluminum Surface-Enhanced Raman Spectroscopy Substrates for Large-Scale 2D Material Characterization

Flexible Plasmonics Using Aluminum and Copper Epitaxial Films on Mica

Microstructure Dictates the Behavior of Plasmons in Nanostructured Ag-Cu Alloy Films

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