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Christian Frydendahl, Sita Rama Krishna Chaitanya Indukuri, Taget Raghavendran Devidas, Zhengli Han, Noa Mazurski, [Kenji Watanabe](https://orcid.org/0000-0003-3701-8119), [Takashi Taniguchi](https://orcid.org/0000-0002-1467-3105), Hadar Steinberg, Uriel Levy

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[hBN‐Encapsulated Graphene Coupled to a Plasmonic Metasurface via 1D Electrodes for Photodetection Applications](https://mdr.nims.go.jp/datasets/1fccbca4-3007-45ac-90d0-bef9f4ede49c)

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hBN-Encapsulated Graphene Coupled to a Plasmonic Metasurface via 1D Electrodes for Photodetection ApplicationshBN-Encapsulated Graphene Coupled to a PlasmonicMetasurface via 1D Electrodes for PhotodetectionApplicationsChristian Frydendahl,* Sita Rama Krishna Chaitanya Indukuri,Taget Raghavendran Devidas, Zhengli Han, Noa Mazurski, Kenji Watanabe,Takashi Taniguchi, Hadar Steinberg, and Uriel Levy*1. IntroductionThe past two decades have seen a rush of new opticaldevices based on 2D material’s unique optical properties.[1–3]There are numerous examples in the literature, fromphotoconductors,[4–7] bolometers,[8–12] photothermovoltaicdevices,[13,14] optical field-effect transistors,[15–17] and hetero-structure devices.[18,19] Photodetectors based on graphene areof particular note, as these devices offer optical detection acrossthe entire electromagnetic spectrum,[1] a result of graphene’sgapless dispersion relation and unique uniform opticalabsorption of ≈2.3% for most wave-lengths.[20] This absorption is however stillfairly low for photodetection purposes, andmuch of the recent literature has thereforefocused on exploring graphene’s integra-tion with different photonic structures[1,3]or methods to pattern graphene itself intoplasmonic nanopatterns to increase opticalabsorption.[21,22]Graphene–photonic structure integra-tion is usually done by placing metallicor dielectric nanostructures directly ontop of or below the grapheme.[1,3,5,23–26]However, an important result in graphenedevice physics has been the fact that it is necessary to encapsulategraphene monolayers between two sheets of the insulating2D material hexagonal boron nitride (hBN) to achieve ideal car-rier transport characteristics.[27,28] This encapsulation ensuresdevices are chemically stable in ambient conditions, as grapheneis protected from atmospheric adsorbates. Encapsulation alsoensures atomically flat graphene sheets, enabling room-temperature ballistic transport.[27] As a result, encapsulation ofgraphene in hBN has rapidly become the standard platform inthe device community and is likely to become the dominant plat-form in a potential future graphene device industry. Additionally,the growing field of twisted bilayer graphene is completelydependent on hBN encapsulation to manufacture the twistedbilayers. The strong van der Waals attraction between grapheneand hBN is what enables the precise angular stacking of one partof a graphene crystal onto itself.[28,29]Furthermore, encapsulation enables the fabrication of 1D“edge contacts” where the graphene sheet is connected to metalelectrodes by a single row of carbon atoms.[27,30,31] Such contactshave shown superior performance in terms of contact resistance,generally attributed to the fact that the edge atoms of the gra-phene sheet are less strongly bonded (due to a lack of neighbor-ing carbon atoms) and thus can more readily accept electronsfrom outside.[30,31] Contact resistance is an important parameterto optimize to ensure fast time-response electronics, due to thefundamental limits imposed by the effective device circuit’s RCtime constant on rise and fall times.However, hBN encapsulation greatly limits how a graphenesheet can be coupled to plasmonic metasurfaces and nanoanten-nas. For example, plasmonic particles need to be positioned closeto direct physical contact with the graphene sheet to enhanceC. Frydendahl, S. R. K. C. Indukuri, Z. Han, N. Mazurski, U. LevyDepartment of Applied PhysicsThe Hebrew University of JerusalemJerusalem 91904, IsraelE-mail: christia.frydendahl1@mail.huji.ac.il; ulevy@mail.huji.ac.ilT. R. Devidas, H. SteinbergThe Racah Institute of PhysicsThe Hebrew University of JerusalemJerusalem 91904, IsraelK. Watanabe, T. TaniguchiAdvanced Materials LaboratoryNational Institute for Materials ScienceTsukuba 305-0044, JapanThe ORCID identification number(s) for the author(s) of this articlecan be found under https://doi.org/10.1002/adpr.202300192.© 2024 The Authors. Advanced Photonics Research published by Wiley-VCH GmbH. This is an open access article under the terms of the CreativeCommons Attribution License, which permits use, distribution andreproduction in any medium, provided the original work is properly cited.DOI: 10.1002/adpr.202300192It is shown here how encapsulated graphene devices can be laterally coupled toplasmonic metasurfaces via 1D edge contacts, preserving the high mobility ofencapsulated graphene while enhancing optical coupling. The device is used forphotodetection applications where high responsivities in the range of 100 AW�1for most of the visible spectrum are reported. The device exhibits a photogatingeffect which is attributed to defect states in the encapsulating hBN layers. Theresults highlight a new configuration to couple graphene with plasmonic structuresand points to a new type of device based on defect states and graphene’s excellenttransport properties to achieve photodetectors with ultrahigh responsivities.RESEARCH ARTICLEwww.adpr-journal.comAdv. Photonics Res. 2024, 5, 2300192 2300192 (1 of 7) © 2024 The Authors. Advanced Photonics Research published by Wiley-VCH GmbHmailto:christia.frydendahl1@mail.huji.ac.ilmailto:ulevy@mail.huji.ac.ilhttps://doi.org/10.1002/adpr.202300192http://creativecommons.org/licenses/by/4.0/http://creativecommons.org/licenses/by/4.0/http://www.adpr-journal.comoptical absorption due to the short spatial extent of their opticalnear fields, and if injection of hot carriers from plasmonic decayis desired, then a direct electrical contact between the two mate-rials is needed.[23,32] As a result, to our knowledge there have notyet been any studies so far into hot electron injection from plas-monic decay[33] into encapsulated graphene.We report here a new type of graphene photodetector, with highresponsivity in the visible regime based on charge injection fromplasmon decay in a gold metasurface to an encapsulated sheet ofgraphene. The metasurface is contacted to graphene via 1D edgecontacts and consists of a pattern of nanodisks/cones. The deviceconfiguration in the present work, a graphene layer doubly encap-sulated by hBN, provides us with a 2D electron gas (2DEG) thathas high carrier mobility and low intrinsic doping.In addition to the hot carrier injection mechanism, we alsoobserve a photogating effect in our device. While it is not fullyclear from our immediate experiments what is the exact mecha-nism causing this, we speculate that it may be related to chargetransfer from defect states that have been generated in the hBNwhere it was etched to form the metasurface. These defects act asartificial atoms and have discrete energy levels.[34,35] While ofgreat interest in their own right, in particular as single-photonemitters for quantum light applications, here we speculate thattheir ability to have intrinsic charge is what is causing a photo-gating effect in our device. Upon being illuminated, the defectstates release their trapped charges and change their chargepolarity, resulting in a different external field affecting the gra-phene when the device is illuminated.[36,37]We report large peak responsivities in the range of≈100 AW�1 and a noise equivalent power (NEP) of ≈100 pW/ffiffiffiffiffiffiffiHzpacross the visible spectrum. It is important to mention thatthe device saturates for even nominal power increases and thusthe responsivity may be even higher for lower optical powersthan the ones tested here, further improving the NEP of thedevice. Our results highlight a new device design where gra-phene can be encapsulated in hBN, yet still be connected to plas-monic nanostructures to retain ideal transport properties.Additionally, the presence of the photogating effect points to anew intriguing class of devices where encapsulated grapheneis coupled to deterministically generated defects in its encapsu-lating hBN.2. ResultsFigure 1a shows a schematic of the device and details themeasurement configuration. The device is a regular encapsulatedgraphene field-effect transistor configuration with 1D edge-contacted source–drain electrodes and a backgate to the siliconsubstrate. In the same etching and metal evaporation step thatdefines the source–drain electrodes, a square lattice of nanodiskshas been patterned. The result after metal evaporation is metaldisks that penetrate into the hBN layers and attach to the gra-phene sheet at its edge atom sites. Optical microscope imagesof a finished device can be seen in Figure 1b,c, which shows scan-ning electron microscopy (SEM) images of another device, and(d)(a) (b)VGASDVSDPin10μm 200nm1μm(c)20μm 20μmMetasurfaceGold electrodeTop hBNBottom hBNτee1 fs 1 psτelγηETFigure 1. Device and working principle. a) Schematic of the device, with illumination scheme and electrical contact scheme detailed. b) Optical micro-scope image of a device. Scale bars are 20 μm. c) SEM image of a device, showing the metasurface dimensions. d) Hot carriers are generated in the goldupon optical absorption, which are then transferred to the graphene. Here they exchange energy with other electrons near the Fermi level, creating acontinuum of hot electrons, before everything relaxes back to the lattice temperature.www.advancedsciencenews.com www.adpr-journal.comAdv. Photonics Res. 2024, 5, 2300192 2300192 (2 of 7) © 2024 The Authors. Advanced Photonics Research published by Wiley-VCH GmbH 26999293, 2024, 4, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adpr.202300192 by National Institute For, Wiley Online Library on [31/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.adpr-journal.comFigure S1 and S2, Supporting Information, show atomic forcemicroscope images of the 2D material layer profiles.As the plasmonic structures are electrically connected to thegraphene by 1D edge contacts, hot carriers generated in the goldcan be transferred to graphene, where these carriers will induce adetectable change in graphene’s conductivity, as shown inFigure 1d. The carrier mobility in graphene is inverselyproportional to the carrier’s energy, μ ∝ 1=E, while the electron–electron scattering time, τee, is in the range of a few femtosec-onds. This means a transferred hot carrier can quickly distributeits energy to multiple carriers near the Fermi level to create acontinuum of hot carriers with a lifetime corresponding to theelectron–lattice scattering time, τel, which in graphene is a fewpicoseconds. Thus the expected effect of hot carrier injectionis an overall reduction in device conductivity.[11,12] Additionally,the transfer of additional electrons to graphene should cause aslight n-doping of the device.[32]To understand where hot carriers could be generated in thesamples, we have performed numerical finite-difference time-domain (FDTD) simulations of the nanodisk array together withthe hBN and graphene stacks. For the geometry, disk diametersof 400 nm and a period of 500 nm were chosen, correspondingto the dimensions of the fabricated device (see Figure S2,Supporting Information). In accordance with the sloped shapeof etched hBN layers (a result of the anisotropy of the reactiveion etching [RIE] process),[27] we have patterned the goldstructures into a flattened inverted pyramid shape. The resultingelectric field map for an incident wavelength of 750 nm can beseen Figure 2a, with the corresponding reflection and absorptionspectra shown in Figure 2b. Absorption was calculated asA ¼ 12 Im½εðx, y, zÞ�jEðx, y, zÞj2, where ε(x,y,z) and E(x,y,z) referto the dielectric function and the electric field in the full 3D spaceof the simulation. Thus, absorption is calculated as a function ofhow much the electric field intensity overlaps with lossy materi-als, such as gold. The reflection was recorded using a field mon-itor above the simulation region. From these simulations we seethat the vast majority of the absorption occurs near the surface ofthe gold nanodisks, not in graphene sheets. This is consistentwith plasmonically enhanced absorption in gold nanodisks.Next, we perform a series of gate sweep measurements on thedevice, while illuminating it with various optical powers from a600 nm laser source. While sweeping the gate voltage, VG, wemaintain a fixed source–drain voltage, VSD= 200mV, and mea-sure the resulting source–drain current, ISD. Some examples ofthe raw measurement data can be seen in Figure 3a. If we focuson the darkmeasurement first (the blue line in Figure 3a), then wesee the characteristic field-effect-induced change of the graphenesheet’s conductivity with the change in applied gate voltage. This isdue to the back-gate-induced charge capacity affecting graphene’sdoping,[17,36] with the characteristic low point of current/conduc-tivity corresponding to charge neutrality found at the applied gatevoltage, VG=VD. Our initial device is slightly n-doped (VD< 0).We see that for higher optical powers, the position of the chargeneutrality point shifts to larger positive values of VG, implyingp-doping of the device with light (as larger amounts of inducedn-doping are required to reach charge neutrality).In terms of optical response of the device, this photodopingeffect serves to enhance device responsivity by horizontally shift-ing the ISD–VG curves. We have included a schematic explana-tion of the effects observed in Figure 3b. Injection of hotcarriers induces a decrease in device mobility, which resultsin a widening of the V-shape of the ISD–VG curve (as the mobilityis proportional to the slope of this curve).[38] While we expected ashift to the left of the charge neutrality point, we observed a shiftto right in our devices. This is indicative a p-doping photogatingeffect.In Figure 3c, we have schematically illustrated how defectstates created by the RIE process used to etch through thehBN encapsulation layers could be responsible. Dry etching/ion bombardment is a well-known method to create opticallyactive defect states in hBN.[34,39,40] We observe wide-band fluo-rescence emission in the visible regime coming from the etchedareas of our devices when illuminating them with an intense532 nm laser, which is a common indication of hBN defectsbeing present.[34,39,40] Such defects can be intrinsically chargedand upon illumination could reverse their polarity due to detrap-ping. Thus, we suspect them to be the main candidate responsi-ble for the observed photogating effect. A similar effect has beenobserved before with quantum dots deposited directly on top of agraphene layer.[37] If we track the shift of the neutrality point ver-sus illumination power, we can also see that this effect saturatesvery rapidly for even nominal incident optical powers, asshown in Figure 3d. This is in agreement with previous obser-vations.[32,37] When measuring the rise- and fall times of a device,(a) (b)grapheneSiO2SihBNhBNAirAuFigure 2. Optical design. a) Field intensity map around 750 nm wavelength and b) Simulated reflection and absorption spectra.www.advancedsciencenews.com www.adpr-journal.comAdv. Photonics Res. 2024, 5, 2300192 2300192 (3 of 7) © 2024 The Authors. Advanced Photonics Research published by Wiley-VCH GmbH 26999293, 2024, 4, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adpr.202300192 by National Institute For, Wiley Online Library on [31/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.adpr-journal.comwe find them to be respectively ≈0.5 and ≈1 s (Figure S3,Supporting Information). Such slow time response is consistentwith the long lifetimes associated with some hBN defect states ofa few ms.[41]We can calculate the device’s optical responsivity asR ¼ Ilight � IdarkPdev(1)with Ilight as the device current under illumination, Idark the darkcurrent, and Pdev is the fraction of the total incident opticalpower, Pin, that hits the device, that is, Pdev ¼ PinAdev=Aspot, withAdev and Aspot respectively being the area of the active deviceregion and the illumination laser spot area. If we plot the respon-sivity as a function of the device gate voltage, VG, and the incidentpower, we get Figure 4a. In terms of optical intensities, we haveilluminated the device area with roughly 41–162.5mW cm�2 inFigure 4a. If we perform line cuts for a constant gate voltage,such as in Figure 4b, we see that the responsivity rapidly satu-rates for even nominal optical powers, both for the positive andfor negative device response regimes. This is consistent with thephotogating effect being the cause of large responsivity. FromFigure 4c, we see that positive and negative regimes fall on eitherside of the charge neutrality point of the device, and theresponsivity is exactly 0 for VG–VD= 0. We call our two differentregimes of photoresponse bolometric and photoconductive(respectively for negative and positive values of R), although thisis more or less just a choice to match convention for the sign ofthe responsivity. The true photoresponse mechanism of ourdevice is likely that of a photogated bolometer.If we track the magnitude of the charge neutrality point shift,Δn, versus the wavelength of the incident laser, we get Figure 5a.By measuring a reflection spectrum from the device metasurfacearea, and assuming the device has 0 transmission (due to siliconsubstrate), the absorption can be found approximately as1� Reflection. Then, we can map the device absorption spec-trum, presented in Figure 5b. There appears to be a general cor-relation, such that increased optical absorption relates to anincrease in charge neutrality point shift.Finally, we characterize the noise spectral density (NSD) of ourdevice’s dark current (see Experimental Section for details), asshown in Figure 5c. From the NSD, we can calculate the NEPas NSD at 1 Hz bandwidth divided by responsivity, and we getFigure 5d. We see that our device has NEP of ≈100 pW/ffiffiffiffiffiffiffiHzp,for the lowest incident powers. In Figure 5e, we show the mobil-ity of a typical device versus induced doping from the gate poten-tial. We see that our device maintains peak mobilities in therange of 7000 cm2 V�1 s�1.(b)(a)(d)SaturationD(c)DefectsVG > 0:VG < 0:Hot electronsLight onLight offInduced p-dopingn-doping p-dopingInduced n-dopingVGISDDefectGoldGraphenehBNHot electronPhotonFigure 3. Optical response of the device. a) ISD versus different gate voltages under different 600 nm laser illumination powers. The sample gets pro-gressively more p-doped with increasing illumination powers. b) Schematic of the optical response. We expect to see n-doping from hot carrier transferfrom plasmonic decay, but the total response is dominated by p-doping. We also see the general reduction in conductivity and device mobility associatedwith hot carrier injection/generation (deeper and wider V-shape in the ISD curve). c) Schematic of physical mechanisms in the device. Defect statescreated during the RIE etching of the hBN could be responsible for the observed p-doping. d) Change in intrinsic charge carrier density, Δn, versusincident optical power. We see that the effect rapidly saturates for increasing power. Dotted line marks a power law fit.www.advancedsciencenews.com www.adpr-journal.comAdv. Photonics Res. 2024, 5, 2300192 2300192 (4 of 7) © 2024 The Authors. Advanced Photonics Research published by Wiley-VCH GmbH 26999293, 2024, 4, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adpr.202300192 by National Institute For, Wiley Online Library on [31/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.adpr-journal.com3. DiscussionA surprising result is the observed p-doping of graphene whenthe device is exposed to light. While the exact cause is outside thescope of this investigation, one potential explanation is the gen-eration of defect states in hBN, when it is exposed to high-energyelectrons during electron beam lithography (≈100 keV) and thensubsequently etched in the RIE step to make 1D electrical con-tacts. hBN hosts a very large variety of potential defect states,many of which hold intrinsic charge, either positive or nega-tive.[42] The most common types are boron or nitrogen vacancies,either with or without carbon substitutions.[43] As our RIE pro-cess directly exposes hBN to carbon in the form of a CHF3plasma, such carbon substitution defects could likely occur inour specific case.When the device is illuminated, the charges trapped in thedefect states can be released and transferred to graphene, wherethey get carried away by the bias voltage. Left behind however arethe oppositely charged defects in hBN, which contribute a smallopposite electrostatic field upon graphene, changing its dop-ing.[44] Another potential explanation is intrinsic defect statesin hBN (from lower-quality hBN crystals) or contaminantstrapped in the hBN/graphene interface during heterostructureassembly. High-spatial-resolution photocurrent maps could helpto clarify this in a future study.A similar photogating of graphene has been reported before,using charge transfer from quantum dots attached to gra-phene,[37] and it seems likely that defects in hBN could servea similar function in our device. When recording Raman spectrato verify the chemical integrity of the graphene after the(a) (b)(c)Figure 4. Responsivity versus incident power. a) Responsivity contour plot for different incident powers with 600 nm and gate potentials. b) Line cutsfrom (a) black dotted line corresponds to the photoconductive regime (positive R) and the white dotted line corresponds to the bolometric regime(negative R). We see that the responsivity rapidly saturates for increasing powers. c) Responsivity versus gate voltage for a fixed incident power.0.20.30.40.50.6Wavelength [nm]057 008056 007055 006500Δn [cm-2]Wavelength [nm]0(a)(b) (d)(c) (e)057 008056 007055 00650051015A [Arb. units]n [cm-2]7000600050004000300020001000000.5 1 1.5-0.5-1-1.5µ [cm2 /Vs]Figure 5. Dirac point shift versus wavelength and noise. a) Shift in Dirac point versus laser wavelength. All points are recorded with 16 μW power. Errorbars correspond to uncertainty on fitting parameters. b) Optical absorption spectra recorded from the device. c) NSD of a device at VG= 0 V. d) NEP forthe responsivity curves shown in Figure 3b. e) Mobility versus induced doping in a device at room temperature without illumination.www.advancedsciencenews.com www.adpr-journal.comAdv. Photonics Res. 2024, 5, 2300192 2300192 (5 of 7) © 2024 The Authors. Advanced Photonics Research published by Wiley-VCH GmbH 26999293, 2024, 4, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adpr.202300192 by National Institute For, Wiley Online Library on [31/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.adpr-journal.comfabrication process (see Figure S4, Supporting Information), wedid notice a significant amount of hBN defect fluorescence(broad visible spectrum emission). As the graphene sheet isexposed over most of its area to etched hBN (along every edgeof the gold nanodisks), the effect of such defect doping wouldbe greatly amplified, even for nominal defect densities in theetched areas.If we calculate the thermal/Johnson current noise asIn;thermal ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi4kBTΔfRss(2)where kB is Boltzmann’s constant, T is temperature, Δf the band-width, and Rs is the serial resistance of our device (≈8 kΩ), we getIn;thermal ≈ 1.44 pA/ffiffiffiffiffiffiffiHzpat a bandwidth of 1 Hz. We see ourdevice is dominated by a general white noise background. Asthe measured NSD at 1 Hz is ≈20 nA/ffiffiffiffiffiffiffiHzp(Figure 5c), whichis significantly higher than the thermal noise, a possibility is thatthe current through the device experiences constrictions/tunnelbarriers at points around the etched areas where the nanostruc-tures are patterned (or even at the main source and drain electro-des), resulting in significant shot noise, similar to a Zener diodenoise generator.In terms of wavelength dependence, we see that the peakresponsivity of the device follows the spectral shape ofFigure 5a,b when illuminating with a fixed power for differentwavelengths, see Figure S5, Supporting Information, for moredetails. This is consistent with the idea of plasmonicallyenhanced absorption and charge transfer from the gold metasur-face, amplifying the graphene’s intrinsic photoresponse.4. ConclusionTo conclude, we have demonstrated how encapsulatedgraphene can be coupled to plasmonic nanostructures via 1Dedge contacts in order to enhance its optical response, while stillmaintaining the high-room temperature mobilities, robustness,and chemical stability associated with hBN-encapsulatedgraphene devices. We report very large responsivities acrossthe visible regime, in the order of hundreds of A/W, althoughwe do see the device rapidly saturating for incident opticalpowers of just a few μW. We report NEP of ≈100 pW/ffiffiffiffiffiffiffiHzpfor low incident power.We also observe an unexplained photogating effect in ourdevices. While we are not strictly able to confirm it, we suspectthat it may be related to defect states in the encapsulatedhBN flakes. These defects are likely created during the fabrica-tion process, which involves exposing the hBN to a high-energyelectron beam and an RIE process involving O2 and CHF3plasmas.[34] Such defects could emulate quantum dots, whichin the past have been observed to cause a photogating effectin graphene.[1,37]5. Experimental SectionDevice Fabrication: hBN multilayers and graphene monolayers (NGSNaturgraphit) were mechanically exfoliated onto silicon substrates with285 nm thermal oxide. From here they were picked up and stacked intohBN/graphene/hBN heterostructures at 100 °C using a home-built 2Dmaterial transfer system with a heating stage[17] using PC/PDMS polymerstamps.[28] After heterostructure assembly, the stacks were dropped off ona clean silicon substrate (highly p-doped) with a 285 nm thermal oxide ontop by melting the PC sacrificial layer at 200°. The samples were thencleaned by soaking them in CHCl3 to remove PC residues. Next, the sam-ples are spin coated with ≈450 nm of PMMA, and electron beam lithog-raphy (Elionix) was used to pattern the metasurface structures and thecontact pads in the PMMA resist. The resist pattern was then etched intothe hBN/graphene/hBN layers using RIE with a mix of O2 and CHF3.[27]The samples were then moved to an electron beam evaporator vacuumchamber where they were left overnight until the chamber pressurereached ≈10�8 bar. Then, 10 nm of Cr followed by 120 nm of Au was evap-orated, followed by lift-off in warm acetone.FDTD Simulations: Periodic arrays of gold nanodisks embedded intohBN/graphene/hBN stacks were simulated using the commercialLumerical FDTD software package (Ansys). Periodic boundary conditionswere used for the x- and y-axes, and the top and bottom of the z-axis wereterminated with perfectly matched layers. Light was injected as a plane-wave source from above the nanodisk, propagating along the negativez-direction. A reflection source monitor was positioned behind the source,and an absorption monitor was placed to encapsulate the whole of thegraphene/gold volumes. The nanodisks had a diameter of 400 nm, witha unitcell period of 500 nm. The substrate consisted of 285 nm SiO2 fol-lowed by an infinite layer of Si. Standard materials from the Lumericallibrary were used.Responsivity and Electrical Measurements: Device responsivity wasmeasured using a home-built reflection microscope and electrical probestation. The sample was excited using a SuperK Extreme supercontinuumlaser (NKT Photonics) monochromated to a spectral width of ≈4 nmaround a central wavelength using a LLTF SWIR-HP8 filter (Fianium).The laser was coupled through the reflection microscope, and the excita-tion power was controlled using two linear polarization filters, with the lastfilter remaining in a fixed position to maintain the laser polarization hittingthe sample. Electrical contacts to the source and drain were made usingtungsten probes and 3D stage micromanipulators, while the back gate tothe silicon was achieved by scratching the back of the Si chip and adheringto the holder via conductive silver paint, and source–drain and bias voltagewere applied using a two-channel B2902A source measure unit (Keysight),with the same unit monitoring the source–drain current during the gatesweep.Optical Reflection Measurements: Optical reflection spectra of the meta-surface devices were measured by illuminating the samples with a whitelight source (tungsten–halogen lamp) through a microscope objective(Nikon, 50�, NA 0.45), and the reflected light was collected with the sameobjective. The light was then spatially filtered with an aperture at the imageplane of the objective to collect light only from the device area to an OceanOptics Flame spectrometer. The recorded reflection spectra were normal-ized to a gold mirror.Supporting InformationSupporting Information is available from the Wiley Online Library or fromthe author.AcknowledgementsC.F. was supported by the Carlsberg Foundation as an InternationalisationFellow during this work.Conflict of InterestThe authors declare no conflict of interest.www.advancedsciencenews.com www.adpr-journal.comAdv. Photonics Res. 2024, 5, 2300192 2300192 (6 of 7) © 2024 The Authors. Advanced Photonics Research published by Wiley-VCH GmbH 26999293, 2024, 4, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adpr.202300192 by National Institute For, Wiley Online Library on [31/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.adpr-journal.comAuthor ContributionsThe project idea was conceived of by C.F. and U.L. Heterostructure assem-bly was done by C.F., S.R.K.C.I., and T.R.D. hBN was synthesized byK.W. and T.T. E-beam lithography and electrode fabrication were doneby N.M., Z.H., and C.F. Scanning electron microscopy images wererecorded by Z.H. Optical and electrical device characterization was doneby C.F. Optical simulations were done by C.F. The manuscript was writtenby C.F. with input from all authors. 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Advanced Photonics Research published by Wiley-VCH GmbH 26999293, 2024, 4, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/adpr.202300192 by National Institute For, Wiley Online Library on [31/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.adpr-journal.com hBN-Encapsulated Graphene Coupled to a Plasmonic Metasurface via 1D Electrodes for Photodetection Applications 1. Introduction 2. Results 3. Discussion 4. Conclusion 5. Experimental Section