15214095, 2022, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/adma.202110099 by Spanish Cochrane National Provision (Ministerio de Sanidad), Wiley Online Library on [14/10/2022]. 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 License Research Article www.advmat.de Atomically Sharp Lateral Superlattice Heterojunctions Built-In Nitrogen-Doped Nanoporous Graphene Maria Tenorio, Cesar Moreno,* Pol Febrer, Jesús Castro-Esteban, Pablo Ordejón, Diego Peña,* Miguel Pruneda,* and Aitor Mugarza* 1. Introduction Nanometer scale lateral heterostructures with atomically sharp band dis- continuities can be conceived as the 2D analogues of vertical Van der Waals Lateral heterostructures combining 2D heterostructures, where pristine properties of each component coexist with materials with distinct properties on a interfacial phenomena that result in a variety of exotic quantum phenomena. covalently bonded, one-atom thick layer However, despite considerable advances in the fabrication of lateral hetero- have been realized by following several structures, controlling their covalent interfaces and band discontinuities with in-situ[1–4] and prepatterning[5] methods. However, despite the plethora of new 2D atomic precision, scaling down components and producing periodic, lattice- materials available, their combination in coherent superlattices still represent major challenges. Here, a synthetic lateral heterostructures is severely lim- strategy to fabricate nanometer scale, coherent lateral superlattice hetero- ited by the lack of epitaxial matching and junctions with atomically sharp band discontinuity is reported. By merging the chemical stability at the interface.[3] interdigitated arrays of different types of graphene nanoribbons by means of a Besides, although methods to fabricate superlattice heterojunctions have already novel on-surface reaction, superlattices of 1D, and chemically heterogeneous been proposed,[2,5] scaling them to the nanoporous junctions are obtained. The latter host subnanometer quantum nanoscale and with atomic precision is dipoles and tunneling in-gap states, altogether expected to promote interfa- beyond their limit. cial phenomena such as interribbon excitons or selective photocatalysis. A natural solution for the aforemen- tioned challenges can be found in the bottom-up, on-surface synthesis of gra- phene-based nanostructures.[6] Following this method, mole- M. Tenorio, C. Moreno, P. Febrer, P. Ordejón, M. Pruneda, A. Mugarza cular precursors of different structure[7–12] and chemical compo- Catalan Institute of Nanoscience and Nanotechnology (ICN2) sition[13–21] can be polymerized to form heterocomponents with CSIC and The Barcelona Institute of Science and Technology tailor designed properties, yet following the graphene backbone Campus UAB, Bellaterra, Barcelona 08193, Spain structure that leads to chemically stable, epitaxial, and covalent E-mail: cesar.moreno@unican.es; miguel.pruneda@icn2.cat; aitor.mugarza@icn2.cat interfaces. In one dimension, different types of graphene-based C. Moreno heterojunctions have been realized by codeposition of two mole- Departamento de Ciencias de la Tierra y Fisica de la Materia cular building blocks,[22–25] or post-synthesis chemical transfor- Condensada mation of functional groups.[26,27] These strategies, however, Universidad de Cantabria albeit defining each component with atomic precision, lead to Santander 39005, Spain either single or randomly distributed heterojunctions, and are J. Castro-Esteban, D. Peña Centro de Investigación en Química Biolóxica e Materiais Moleculares hard to be extrapolated to 2D structures. Moreover, despite the (CiQUS) atomic sharpness of the interface structure, the charge redistri- Departamento de Química Orgánica bution and corresponding band discontinuity gradually evolve Universidade de Santiago de Compostela within several atomic sites across the junction,[22,23] limiting the Santiago de Compostela 15782, Spain downscalability of superlattices or multijunctions.[27] E-mail: diego.pena@usc.es Extending a recently proposed on-surface method to syn- A. Mugarza ICREA Institució Catalana de Recerca i Estudis Avançats thesize nanoporous graphene (NPG)[28] to a two-component Lluis Companys 23, Barcelona 08010, Spain sequential growth procedure, we have devised a strategy to The ORCID identification number(s) for the author(s) of this article assemble 2D lateral heterojunctions, where the component size, can be found under https://doi.org/10.1002/adma.202110099. interface, and band discontinuity are all designed with atomic © 2022 The Authors. Advanced Materials published by Wiley-VCH precision. The heterostructure can be likewise perceived as a GmbH. This is an open access article under the terms of the Creative hybrid nanoporous graphene (h-NPG) with a chemically hetero- Commons Attribution-NonCommercial-NoDerivs License, which geneous pore structure. The key ingredient to achieve this is a permits use and distribution in any medium, provided the original work double templating effect that guides the synthesis of each of the is properly cited, the use is non-commercial and no modifications or adaptations are made. components. The first component is a graphene nanoribbon (GNR1) that grows in parallel arrays guided by the template DOI: 10.1002/adma.202110099 provided by the substrate.[29] In a second step, the GNR1 array Adv. Mater. 2022, 34, 2110099 2110099 (1 of 9) © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH 15214095, 2022, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/adma.202110099 by Spanish Cochrane National Provision (Ministerio de Sanidad), Wiley Online Library on [14/10/2022]. 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 License www.advancedsciencenews.com www.advmat.de acts as a dynamic template, defining reactor nanochannels for atom size components with well-defined pristine properties can the synthesis of the second nanoribbon component (GNR2), coexist with emergent interfacial quantum properties. and fusing with the latter to form [GNR1-GNR2]n lateral super- lattice heterojunctions. The localization of pyrimidine groups at the edges of GNR2, together with the particular interribbon 2. On-Surface Synthesis of the Nanoporous coupling geometry, results in an overall nanoporous graphene Graphene structure where the chemical heterogeneity is introduced with atomic precision at the pore edges. The main steps of the process are summarized in Figure 1. In contrast to the random distribution of heterojunctions The first component, GNR1, is the 7-13-AGNR that can be obtained by the longitudinal assembly of codeposited 1D GNR synthesized on an Au(111) surface using 10,10′-dibromo-2,2′- components, our interdigitation strategy enables the formation diphenyl-9,9′-bianthracene (1), and following the widely used of atomically precise 2D superlattice heterostructures. On the two-step Ullmann polymerization and cyclodehydrogenation other hand, the correlated subnanometer localization of dipolar (CDH) reaction sequence.[10,28,29] The corresponding onsets charges and the single CC bond band discontinuity, together for the two thermally induced reactions are T1 = 200 °C and with the localization of frontier bands at the backbone of the T2 = 400 °C, respectively. As previously reported, the potential nanoribbons, facilitate the scaling of the superlattice period grid formed by the herringbone reconstruction of the Au(111) down to 1 nm, a scale so far inaccessible to both the on-sur- surface guides the synthesis of this GNR forming periodic face synthesis of graphene nanostructures and the sequential arrays.[29] Three different periods can be obtained depending growth strategy used for 2D materials. The resulting lateral on the coverage, d1 = 7.8 nm, d2 = 3.8 nm, and d3 = 1.9 nm superlattice heterostructures can therefore be conceived as for 0.5 ML, 0.75 ML, and 1 ML, respectively (1 ML corresponds the 2D analogues of the vertical heterostructures, where a few to the saturation of the d3 phase by definition). The optimal Figure 1. Schematic illustration of the bottom-up fabrication of the superlattice heterojunction built-in a h-NPG. a) GNR1 is synthesized by depositing precursor 1 on Au(111) at room temperature and following the Ullmann polymerization and cyclodehydrogenation (CDH) steps at T1 = 200 °C and T2 = 400 °C, respectively, as reported in Ref. [28]. The ribbons form a 1D array using the herringbone reconstruction of the Au(111) surface as template (see Ref. [29]). b) The GNR1 array serves as a second template to host precursor 2 on the empty Au(111) tracks and guide the synthesis of GNR2. Ullmann polymerization at T1* = 150 °C, and a simultaneous CDH of poly-2 into GNR2 and the unprecedented interribbon HCl zipping at T2* = 300 °C lead to a hybrid nanoporous graphene with heterogeneous pore structure and a built-in [GNR1-GNR2]n superlattice heterojunction (c). Adv. Mater. 2022, 34, 2110099 2110099 (2 of 9) © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH 15214095, 2022, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/adma.202110099 by Spanish Cochrane National Provision (Ministerio de Sanidad), Wiley Online Library on [14/10/2022]. 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 License www.advancedsciencenews.com www.advmat.de GNR1 coverage in order to maximize the area of the final The presence of a chlorine atom on each pyrimidine ring h-NPG is determined by the intercalation of precursor 2, which not only reduces the interribbon cross-coupling, but also the imposes a superlattice periodicity of 2.5 nm before shrinking internal CDH of poly-2 into GNR2, which are triggered simul- into the covalently fused h-NPG (see Figure S6, Supporting taneously at T2* = 300 °C (Figure 2c). The periodicity of 1.7 nm Information, and discussion below). This average periodicity measured for the resulting interdigitated [GNR1-GNR2] super- corresponds to a GNR1 coverage of 0.76 ML. We therefore use lattice patches are close to the nominal value of 1.6 nm of the GNR1 arrays of densities close to this value for the synthesis of covalently bonded GNR array that form h-NPG (see Figure S6, the second component. Supporting Information). Although most of the patches we find For the second component we designed and synthe- consist of 4–5 coupled GNRs, we can find larger patches with sized 10,10′-dibromo-2,2′-bis(2-chloropyrimidin-5-yl)-9,9′- up to 9–10 coupled GNRs (see Figure S8, Supporting Informa- bianthracene (2), a pyrimidine-substituted bianthracene deriva- tion). Bond resolved (BR-) STM images acquired with a CO- tive (details of the monomer synthesis in Experimental Section functionalized tip as the one shown in Figure 2d demonstrate and Figures S1–S5, Supporting Information). This GNR pre- the coupling of adjacent GNRs, and enable the direct visu- cursor, being isostructural to 1, bears two important differences: alization of the chemically heterogeneous nanopores defining the pyrimidine rings that substitute the phenyls of 1, and the the junctions by revealing clear chemical contrast between the introduction of chlorine atoms in these lateral rings. The pyrim- bridging units of the two components, as illustrated by the line idine introduces chemical heterogeneity to the nanopores, and profiles of Figure 2d. is expected to modify the electronic band structure of the final GNR2, and consequently of the whole h-NPG. Pyrimidinic N is an isoelectronic substitution that does not introduce additional 3. Electronic Characterization of the Superlattice charges, but its higher affinity results in a local charge accu- Heterostructure mulation and the corresponding inductive band shift.[23,30] (see Figure S12, Supporting Information). The role of the chlorine The interdigitated GNRs defining the h-NPG imprint a stag- substituents, on the other hand, is to reduce the temperature gered (type II) superlattice heterojunction band structure with of the final interribbon lateral cross-coupling in order to assure atomically sharp discontinuities. The band gaps and disconti- the survival of the pyrimidine group throughout all the reaction nuities can be directly probed by measuring the local density sequence. We do that by substituting the dehydrogenative CC of states (LDOS) within each type of nanoribbon by scanning coupling that requires temperatures of ≈450 °C,[28] high enough tunneling spectroscopy (STS). The dI/dV spectra of Figure 3a to cleave or decompose edge functional groups,[20,21] by a HCl reveal a pair of peaks that can be assigned to the valence band zipping mechanism that emulates the recently reported HF maxima (VBM) and conduction band minima (CBM) of each zipping and can already be triggered at the CDH reaction tem- component, aided by the identification of features related to perature of 300 °C.[31,32] This reduction of 100 °C, as compared these states in corresponding dI/dV maps (see Figure S11, to the HF zipping observed on the same surface, is crucial for Supporting Information). Our analysis leads to similar band the synthesis of heterogeneous structures as the one demon- gaps of 1.25 eV for GNR1 and 1.47 eV for GNR2, with the strated in this work, since most heterogeneous moieties cannot VBM and CBM, respectively, downshifted by 0.41 and 0.19 eV withstand the 400 °C needed for the HF zipping.[19,20] We for GNR2, as expected for the N-doped component.[23,30] The envision that this temperature reduction can also be crucial to magnitude of the valence and conduction band offsets is well promote the synthesis of covalent nanostructures on less reac- captured by a similar shift of 0.42/0.41 eV found for the VBM/ tive insulator surfaces, as recently demonstrated by using the CBM in the density functional theory (DFT) band structure HF zipping.[31] shown in Figure 3c. We attribute the differences found in the The scanning tunneling microscopy (STM) image of experimental band gaps to the different degree of screening of Figure 2a shows that precursor 2 deposited at room tempera- substrate electrons in each case, which can be due to a more ture already intercalate in the interribbon channels (see Figure effective decoupling of the N-doped GNR, as recently found in S6, Supporting Information, for more details). By annealing to zigzag GNRs.[34] T1* = 150 °C, precursor 2 undergoes Ullmann polymerization, This substantial band discontinuity exerts an effective con- exhibiting the characteristic chain of alternating lobes that can finement of the frontier bands of each heterocomponent, as be seen in Figure 2b.[10] Besides some marginal regions where can be visualized in the constant current dI/dV maps and con- short, meandering poly-2 chains cluster (see Figure S7, Sup- stant height LDOS cuts shown in Figure 3d. However, the cor- porting Information), the surface is covered with an interdigi- responding wave functions of the interdigitated components do tated [GNR1-(poly-2)]n superlattice. The longer, straight, poly-2 not completely vanish at adjacent GNRs (Figure 3d bottom). In chains in the interdigitated region suggest that the reactor particular, the VBM of GNR1 and CBM of GNR2 extend across nanochannels provided by the GNR1 array can be employed as adjacent GNRs as faint diagonal stripes, even if these are for- a general strategy to assist polymerization of precursors that bidden gap regions. We attribute it to the tunneling of these lead to undesired intermolecular interactions on a 2D template, states across the junction, which can also be perceived in the as is the case of many functionalized molecules.[33] The single DOS of Figure 3c for a high enough amplification (dashed periodicity of 2.5 nm measured by STM for the interdigitated lines). The tunneling contributions are not detected in the dI/ superlattice indicates that GNR1-(poly-2) interactions unpin dV and LDOS maps due to the fact that their weak signal is fur- the GNR1 superlattice from the herringbone template (see ther attenuated by the faster decay of the wave function into the Figure S6, Supporting Information). vacuum at the backbone of GNRs.[35] Adv. Mater. 2022, 34, 2110099 2110099 (3 of 9) © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH 15214095, 2022, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/adma.202110099 by Spanish Cochrane National Provision (Ministerio de Sanidad), Wiley Online Library on [14/10/2022]. 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 License www.advancedsciencenews.com www.advmat.de Figure 2. STM characterization of the on-surface synthesis of h-NPG. a–c) Synthesis of GNR2 within the GNR1 array. The STM topographic images show: a) intercalated monomers of 2 after deposition at room temperature. b) Formation of poly-2 chains interdigitated within the GNR1 array after annealing at T1* = 150 °C. c) Simultaneous cyclodehydrogenation (CDH) and interribbon cross-coupling by HCl zipping, which leads to the [GNR1- GNR2]n superlattice heterostructure, after annealing at T2* = 300 °C. Top/bottom images represent large and small scale areas, not necessarily of the same region. d) BR-STM of a [GNR1-GNR2-GNR1] triplet obtained with a CO-functionalized tip unveiling clear chemical contrast between the bridging pyrimidine rings of the N-doped GNR2 (center ribbon) and the benzene rings of the undoped GNR1 (side ribbons). The significantly lower contrast of the pyrimidine rings is clearly visualized at the transversal profiles obtained at the lines marked in the STM image. All imaging parameters are detailed in Table S1, Supporting Information. In-gap tunneling states have been predicted to exist in well- sharp potential steps and the presence of tunneling states. defined heterojunctions with an atomically sharp potential Figure 3b shows a series of constant current dI/dV spectra step.[36] In a more detailed analysis of our experimental and acquired across a GNR1-GNR2 interface. Here, the CB+1 theoretical data, we find evidences for both, the atomically maxima exhibit a sharp discontinuity at the interface within Adv. Mater. 2022, 34, 2110099 2110099 (4 of 9) © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH 15214095, 2022, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/adma.202110099 by Spanish Cochrane National Provision (Ministerio de Sanidad), Wiley Online Library on [14/10/2022]. 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 License www.advancedsciencenews.com www.advmat.de Figure 3. Electronic band structure of h-NPG. a) Representative dI/dV spectra of GNR1 and GNR2, where the VBM and CBM are marked with dashed vertical lines (positions of the selected spectra are highlighted with white outline in the series of Figure 3b). The corresponding band gap is indicated. A spectrum acquired on Au(111) is included as reference (shadowed grey line). b) Color plot of a series of constant current dI/dV spectra acquired along a line that crosses a GNR1-GNR2 pair within the triplet shown in Figure 2d. The topographic profile along the spectroscopic series is overlaid as white line. c) DFT band structure of the [GNR1-GNR2]n superlattice. Colored fat bands represent the projection onto GNR1 (red) and GNR2 (blue). The DOS of each heterocomponent is added on the left. d) Constant current dI/dV maps and constant height LDOS cuts at VBM and CBM energies, and the corresponding wave functions. The LDOS cuts are at the height of h = 0.3 nm. Represented wavefunctions have been integrated from the nodal plane (y = 0) to infinite. Red/blue colors correspond to +/- values. The topographic images where the maps were acquired are shown at the left, overlapped with a schematic illustration that includes the superlattice band offsets. All STS parameters are detailed in Table S1, Supporting Information. the step size of 0.15 nm, a single CC bond, used in the spec- the strong overlap of the tails of the VBM of GNR1 coming troscopic series. This value is significantly smaller than the from each heterojunction into the central GNR2 region. This already narrow band bending region found in 0D heterojunc- overlap is the origin of the “stripes” that connect the VBM/ tions in graphene nanoribbons.[23,26] The CBM of both compo- CBM wave functions in the periodic superlattice of Figure 3d. nents also show constant energy levels, separated by ≈0.2 eV, In order to study the evolution of the overlap with the period of but in this case they interpenetrate across the interface, which the superlattice, in Figure 4b we analyze squared wave function we tentatively attribute to tunneling. The decay of the tunneling profiles for [(GNR1)m-(GNR2)m]n heterojunctions of different tail can be better studied in simulated log scale LDOS scans, periodicity w = m × d (d = 1.6 nm is the inter-ribbon distance as the one shown in Figure 4a for a [GNR1-GNR2-GNR1] tri- in the superlattice). For the superlattice that we synthesized, plet. The finite segment allows us to simultaneously visualize the m = 1, a small but finite overlap of the in-gap tails within the decay of CBM states of GNR2 within the GNR1 region, and the single ribbon components (blue line sections) can be clearly Adv. Mater. 2022, 34, 2110099 2110099 (5 of 9) © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH 15214095, 2022, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/adma.202110099 by Spanish Cochrane National Provision (Ministerio de Sanidad), Wiley Online Library on [14/10/2022]. 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 License www.advancedsciencenews.com www.advmat.de Figure 4. In-gap states and quantum dipoles. a) Simulated LDOS scan across a GNR1-GNR2-GNR1 triplet. The path of the scan line is indicated with colored atoms on the schematic on top. The color plot is in log scale to enhance in-gap states within the gap. b) Profiles of the square of the wave functions of the VBM of GNR1 averaged along the ribbon direction for m = 1–3 superlattices, showing the evolution of the decaying in-gap tail at GNR2. The green line is an envelope guideline. c) Hirshfeld charge difference with respect to individual GNR1 and GNR2, averaged in columns along the ribbon direction. The sum over half segments of the ribbons defines the dipolar charge ±|∆Q|. The charge difference at each atom is also depicted in red/blue (+/-) color scale. d) Evolution of the dipolar charge and band offset with the superlattice period, the latter measured at the VBM. The band offset data is fitted with the inverse law model of Ref. [37]. The dashed line in the top graph refers to dipolar charge of the m = 1 superlattice, and in the bottom graph to the band shift of the infinite superlattice. perceived. For superlattices with wider heterocomponents (m superlattice heterostructures with periodicity w larger than the > 1), the distance between junctions is enough to prevent any interfacial dipole, the potential decays as 1/w. Consequently, for significant overlap, leading to an effective disconnection of periods smaller than the characteristic decay length, which can the interdigitated GNRs (see Figure S10, Supporting Informa- be as large as 30 nm for semiconductor heterojunctions such tion, for corresponding 2D wave functions plots). Notably, the as MoS2/WS2,[37] the band offset is size-dependent. In narrow bridges that couple GNR2 units introduce step discontinui- superlattices the interaction between adjacent dipoles can also ties that further attenuate the decay. This is evident for m = 3, lead to charge redistributions that induce additional shifts.[27] where the in-gap state abruptly decays to negligible values These two factors demand an accurate control on the superlat- when entering the central GNR2 unit (follow guiding green line tice quality for a homogenous, well-controlled band offset. In sections in Figure 4b). order to discern the different mechanisms for band realign- Interfacial in-gap states are inherently associated with a ment, we tracked the evolution of both the dipole charge and charge redistribution, which can induce significant band rea- band offset with respect to the superlattice period. Figure 4d lignment.[36] Unlike conventional bulk heterostructures, the shows that the dipole charge |∆Q|, as obtained from the Hirsh- interfacial dipole potential of 1D (lateral) heterojunctions feld charge difference integrated in half segment of each type decays logarithmically with the distance from the junction. In of ribbon (see Figure 4c), remains nearly constant down to the Adv. Mater. 2022, 34, 2110099 2110099 (6 of 9) © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH 15214095, 2022, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/adma.202110099 by Spanish Cochrane National Provision (Ministerio de Sanidad), Wiley Online Library on [14/10/2022]. 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 License www.advancedsciencenews.com www.advmat.de narrowest superlattice m = 1. This is a further manifestation of STM (BR-STM). All conditions for image acquisition are summarized in the strong localization of the quantum dipoles that characterize Table S1, Supporting Information. For the tip functionalization, CO molecules were first introduced on these heterojunctions, estimated to be within two carbon bond- the Au surface by dosing the cryostat with CO gas at a pressure of 5 × lengths from the interface, well below the narrowest superlat- 10−7 mbar for 30 s in a temperature range from 5 to 15 K. The CO was tice period of 1.6 nm. This result is in contrast with the signifi- then picked up by the tip by applying pulses of 2.5 V at random positions cant charge redistribution found for 0D heterojunctions of sim- or by gentle tip indentations on the Au surface until the resolution was ilar width within single GNRs.[27] Confirming the rigid dipole suddenly improved. The higher resolution of these tips are related to scenario, the band realignment evolution follows the inverse dynamic effects in the CO-metallic tip junction as it interacts with the scaling down to m = 1 (see Figure 4d). The fit of the data results atoms beneath.[47] dI/dV conductance maps in Figure 3 were acquired in CC mode with in a decay length of 7.8 nm, measured as the period where the a standard metallic tip using a lock-in technique. All the parameters are band offset deviates 10% from the asymptotic value of 0.34 eV listed in Table S1, Supporting Information. of the infinite superlattice. The I–V conditions of the STM images of Figures S6 and S7 are listed in Table S2, Supporting Information. DFT Calculations: All the electronic structure analysis in this work has been performed with DFT calculations using the SIESTA code.[48–50] For 4. Conclusions the simulations the authors used the PBE form of the GGA exchange- correlation functional, with an optimized DZP basis set with diffuse In conclusion, our synthetic method provides a route to realize orbitals for C and H atoms and the default DZP basis set for N with an lateral superlattice heterojunctions with an atomically sharp energy shift of 0.01 Ry. The structures were relaxed up to a force tolerance step potential and nanometer scale period that is well below of 0.01 eV Å−1. To avoid interactions between periodic replicas of the 2D the screening length of the interfacial dipole. The band offset layer, a large vacuum region ≈35 nm was included in the simulation box. is controlled by the atomic scale design of the components and The mesh cut-off was set to 400 Ry. To sample the reciprocal space, they used a Monkhorst–Pack grid with 30 k points in the longitudinal the strong localization of the interfacial quantum dipoles. The (ribbon) direction and at least 3 k points in the transversal direction. sharp band discontinuity together with the presence of tun- Post processing of the results was done using the sisl python package.[51] neling states at both sides of the junction is expected to pro- Theory Calculations Processing: PDOS curves in Figure 3c have been mote interribbon excitons, the 1D analogue[38] of interlayer obtained with a 60 × 30 × 1 k point sampling and smoothed out using excitons in vertical heterostructures,[39–43] as well as efficient a Gaussian with σ = 0.05 eV. All the wave functions displayed in this charge separation that can be relevant for optoelectronics and work were integrated over the Z axis from the position of the NPG excitonic solar cells.[44] The coexistence of a type II superlattice sheet to the vacuum (only on one side of the monolayer in order to keep phase information). The longitudinal ribbon direction (Y) is also band structure with heterogeneous nanopores at the junction integrated whenever the wave function is plotted along the superlattice makes this graphene-based nanomaterial particularly attrac- axis (X) only. In the case of the LDOS displayed in Figure 3d, the authors tive for photocatalytic applications such as water splitting.[45] only considered a small range from 3 to 3.5 Å above the NPG sheet to Furthermore, the N-doped nanopores of the one atom thick compare with the STM images. For the LDOS in Figure 4a, a Gaussian hybrid layer could be relevant for membrane applications such convolution with σ = 0.1 eV has been applied to the energy axis to get as selective ion sieving.[46] a smoother visualization. In the analysis of atomic charges, each bar represents the integrated contributions of a “YZ” plane placed at the center of the bar, with each atom contributing to its nearest plane. Statistical Analysis: Topographic images have only been treated 5. Experimental Section with plane subtraction, rotation, and zooming when necessary, except Synthesis of the Molecular Precursors by Means of Solution Chemistry Figure 2a, top, and Figure S6c (inset), Supporting Information, which (General Methods): All reactions were carried out under argon using have been also smoothened with a 3 × 3 matrix convolution. Scanning oven-dried glassware. TLC was performed on Merck silica gel 60 F254; tunneling spectroscopy (STS) spectra from Figure 3a have been averaged chromatograms were visualized with UV light (254 and 360 nm). Flash with the respective forward and backward spectra, and it has been column chromatography was performed on Merck silica gel 60 (ASTM smoothed by linear interpolation with a total number of 2000 points 230–400 mesh). 1H and 13C NMR spectra were recorded at 300 and and 150 nodes. Representative values were selected for the distances 75 MHz or 500 and 125 MHz (Varian Mercury 300 or Bruker DPX-500 between GNRs in the intermediate and final stages in Figure S6, instruments), respectively. APCI spectra were determined on a Bruker Supporting Information. For the GNRs center-to-center distance, profiles Microtof instrument. A detailed description of the synthetic route for were extracted from images using the WSxM program.[52] each molecular precursor can be found in the Supporting Information. Sample Preparation: The Au(111) single crystal was prepared by repeated sputter-anneal cycles using Ar+ ions at an energy of 1 keV and annealing to 470 °C. The precursor 1 was sublimated at 270 °C Supporting Information with a deposition rate of 0.1 monolayer/min and with the Au(111) held Supporting Information is available from the Wiley Online Library or at 200 °C, whereas precursor 2 was sublimated at the temperature of from the author. 320 °C with a deposition rate of 0.006 ML min−1 and the Au(111) substrate at room temperature, both from the same commercial Dodecon OMBE fourfold Knudsen cell. The sample temperature was measured by using a thermocouple directly in contact with the sample. The base pressure Acknowledgements during evaporation was below 1 × 10−9 mbar. Scanning Tunneling Microscopy and Spectroscopy: The images of This research was funded by the CERCA Programme/Generalitat Figure 2 (except c Bottom and d) were acquired in constant current de Catalunya and supported by the Spanish Ministry of Economy (CC) mode and without any intentional functionalization of the tip apex. and Competitiveness, MINECO (Grant No. SEV-2017-0706), Grants Images in Figures 2c, bottom, and 2d were acquired in constant height PID2019-107338RB-C65, and PID2019-107338RB-C62, funded by MCIN/ (CH) mode, and with a CO-functionalized tip to perform bond-resolved AEI/ 10.13039/501100011033, Grant PGC2018-096955-B-C43 funded by Adv. Mater. 2022, 34, 2110099 2110099 (7 of 9) © 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH 15214095, 2022, 20, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/adma.202110099 by Spanish Cochrane National Provision (Ministerio de Sanidad), Wiley Online Library on [14/10/2022]. 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 License www.advancedsciencenews.com www.advmat.de MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making [7] J. Cai, P. Ruffieux, R. Jaafar, M. Bieri, T. Braun, S. Blankenburg, Europe”, FLAG-ERA grant LEGOCHIP Projects PCI2019-111890-2 and M. Muoth, A. P. Seitsonen, M. Saleh, X. Feng, K. Müllen, R. Fasel, PCI2019-111933-2 funded by MCIN/AEI /10.13039/501100011033 and Nature 2010, 466, 470. cofounded by the European Union, the GenCat (Grant No. 2017SGR1506), [8] D. G. de Oteyza, A. García-Lekue, M. Vilas-Varela, N. Merino-Díez, the European Union MaX Center of Excellence (EU-H2020 Grant No. E. Carbonell-Sanromà, M. Corso, G. Vasseur, C. Rogero, E. Guitián, 924143), the European Regional Development Fund (ERDF) under the J. I. Pascual, J. E. Ortega, Y. Wakayama, D. Peña, ACS Nano 2016, program Interreg V-A España-Francia-Andorra (Grant No. EFA 194/16 10, 9000. TNSI), and Xunta de Galicia (Centro Singular de Investigación de Galicia [9] J. Liu, B.-W. Li, Y.-Z. Tan, A. Giannakopoulos, C. Sanchez-Sanchez, accreditation 2019–2022, ED431G 2019/03). C.M. was supported by D. Beljonne, P. Ruffieux, R. Fasel, X. Feng, K. Müllen, J. Am. Chem. Grant RYC2019-028110-I funded by MICIN/AEI/ 10.13039/501100011033 Soc. 2015, 137, 6097. and by “ESF Investing in your future”. M.T. has been supported by [10] C. Moreno, M. Panighel, M. Vilas-Varela, G. Sauthier, M. Tenorio, Spanish State Research Agency/FSE (ref. BES-2017-08078, project ref. SEV-2013-0295-17-2). The authors thankfully acknowledge the computer G. Ceballos, D. Peña, A. Mugarza, Chem. Mater. 2019, 31, 331. resources at MareNostrum and the technical support provided by [11] O. Gröning, S. Wang, X. Yao, C. A. Pignedoli, G. Borin Barin, Barcelona Supercomputing Center (RES-QCM-2019-1-0051). C. Daniels, A. 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