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Yuya Fukuta, Souren Adhikary, [Kazuhito Tsukagoshi](https://orcid.org/0000-0001-9710-2692), [Katsunori Wakabayashi](https://orcid.org/0000-0002-9147-9939)

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[Dilute magnetism and edge-state engineering in monolayer SnO](https://mdr.nims.go.jp/datasets/cb34442a-8eb6-4bd4-b02f-51b6422b56e8)

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Dilute magnetism and edge-state engineering in monolayer SnONanoscaleAdvancesPAPERPublished on 02 June 2026Licensed under CC-BY 4.0Dilute magnetismaDepartment of Nanotechnology for SustaTechnology, Kwansei Gakuin University, GabResearch Center for Materials NanoarchiMaterials Science (NIMS), Namiki 1-1WAKABAYASHI.Katsunori@nims.go.jpcCenter for Spintronics Research Network (C8531, JapanCite this:Nanoscale Adv., 2026,8, 4101Received 20th February 2026Accepted 23rd May 2026DOI: 10.1039/d6na00140hrsc.li/nanoscale-advances© 2026 The Author(s). Published byand edge-state engineering inmonolayer SnOYuya Fukuta,a Souren Adhikary,a Kazuhito Tsukagoshi band Katsunori Wakabayashi *abcTin monoxide (SnO) is a p-type oxide semiconductor whose electronic properties can be widely modifiedvia atomic-scale engineering. Using density functional theory, we investigate the electronic and magneticproperties of a transition-metal (TM=Mn, Fe, Co andW) doped SnOmonolayer within a large supercell. Wefind that all dopants induce finite localized magnetic moments, primarily originating from d-orbitals of theimpurity atoms. We show that these localized magnetic states give rise to nearly dispersionless bands in thevicinity of the Fermi energy (taking Co doped SnO as an example). In addition, we investigate dimensionaleffects by constructing nanoribbon geometries of the SnO monolayer. The ribbons exhibit intrinsic edge-localized states that are largely independent of ribbon width. For chiral nanoribbons oriented along a low-symmetry direction of the square lattice, we find that oxygen-rich edges are thermodynamically the moststable and remain semiconducting, whereas Sn-terminated edges host metallic one-dimensionalconduction channels. Our results demonstrate that transition-metal doping and edge engineeringprovide effective routes to tailor the electronic properties of the SnO monolayer, making it a promisingcandidate for future spintronic and nanoelectronic applications.1. IntroductionTransparent and exible electronics based on oxide semi-conductors have been extensively investigated owing to theirwide band gaps, chemical stability, and compatibility with low-temperature processing technologies, as summarized in severalcomprehensive reviews.1–5 While high-performance n-type oxidesemiconductors are now well established, the realization ofcomplementary transparent electronic circuits remains chal-lenging due to the limited availability of p-type oxide semi-conductors with sufficient carrier mobility and stability.Among candidate p-type oxides, tin monoxide (SnO) isparticularly attractive because the stereochemically active Sn2+lone-pair states hybridize with O 2p orbitals, resulting in rela-tively dispersive valence-band states. Such lone-pair-drivenband dispersion has been recognized as a key design prin-ciple for achieving p-type conductivity in oxide semi-conductors.3 First-principles studies have further shown thatmonolayer SnO is dynamically stable and exhibits a moderateband gap together with high intrinsic hole mobility, making ita promising platform for two-dimensional (2D) oxideinable Energy, School of Science andkuen-Uegahara 1, Sanda 669-1330, Japantectonics (MANA), National Institute for, Tsukuba 305-0044, Japan. E-mail:SRN), Osaka University, Toyonaka 560-the Royal Society of Chemistryelectronics.6 The electronic properties of SnO are further foundto be highly sensitive to atomic-scale perturbations such asstrain, native defects, and surface chemistry, which can intro-duce in-gap states and modify carrier transport.7,8Beyond intrinsic band-structure considerations, carriertransport and stability in oxide semiconductors are known to bestrongly inuenced by oxygen-related defects and dopantchemistry. Experimental studies on In2O3-based amorphousoxide semiconductors have demonstrated that controlledsuppression of oxygen vacancies and appropriate dopantincorporation are crucial for achieving stable and high-mobilitytransport characteristics in thin-lm transistor devices.9–11These experimental ndings establish general design principlesfor oxide semiconductors that are also relevant to low-dimensional SnO systems. Recent experiments have demon-strated that tin monoxide can be stabilized in the atomicallythin limit, retaining p-type conduction down to thicknesses ofonly a few atomic layers. This experimental realization estab-lishes SnO as a viable 2D oxide platform, rather than a purelytheoretical model system.12A powerful strategy to further expand the functional land-scape of SnO is transition-metal (TM) doping. Substitutionalincorporation of 3d TM atoms has been predicted to introducelocalized impurity states and magnetic moments, giving rise tospin-polarized electronic structures in the otherwise nonmag-netic SnO.13–15 In general, TM doping can induce dilute ferro-magnetic or antiferromagnetic states in the host monolayer.16,17In particular, cobalt doping has been proposed as a promisingNanoscale Adv., 2026, 8, 4101–4108 | 4101http://crossmark.crossref.org/dialog/?doi=10.1039/d6na00140h&domain=pdf&date_stamp=2026-07-11http://orcid.org/0000-0001-9710-2692http://orcid.org/0000-0002-9147-9939https://creativecommons.org/licenses/by/4.0/Nanoscale Advances Paperroute to generate exchange-split Co-derived states near theFermi level in SnO-based systems.18,19 Most previous theoreticalstudies have primarily relied on density-of-states analysis.However, electronic transport properties are strongly inuencedby band dispersion. Therefore, in this work, we examinetransition-metal doping in SnO monolayers by analyzing theband structure in addition to the density of states.Reducing SnO to nite-width nanostructures introduces anadditional design degree of freedom through edgeformation.20–22 In a square-lattice system such as SnO, nano-ribbons can be constructed along high-symmetry crystallo-graphic directions as well as along low-symmetry (off-axis)directions with respect to the underlying lattice. Edges orientedalong low-symmetry directions provide atomic congurationsthat are fundamentally distinct from high-symmetry termina-tions, leading to modied local coordination environments andpotentially giving rise to unconventional edge-localized elec-tronic states. Despite their importance, the electronic proper-ties of such low-symmetry edges in SnO nanoribbons have notyet been systematically investigated.In this work, we employ rst-principles density functionaltheory calculations to systematically investigate the combinedeffects of transition-metal doping and edge engineering inmonolayer SnO. We nd that all TM dopants induce nitemagnetic moments, primarily originating from localized d-orbitals of the impurity atoms. In particular, substitutional Codoping introduces strongly spin-polarized mid-gap states nearthe Fermi level. Notably, these mid-gap states exhibit nearlydispersionless (at) bands in the vicinity of the Fermi level. Theinclusion of on-site Coulomb interaction reveals a correlation-driven splitting of these at bands, highlighting the impor-tance of electron–electron interactions in accurately describingthe electronic structure. Furthermore, we show that the di-spersionless bands in Co-doped SnO lead to a reduced ampli-tude of the optical conductivity compared to the pristine SnOmonolayer. In addition, we show that SnO nanoribbons exhibitintrinsic edge-localized states that are largely independent ofribbon width. Furthermore, nanoribbons with low-symmetryedge orientations exhibit a tunable transition between semi-conducting and metallic behavior, depending on the atomictermination. These results establish atomistic design principlesfor controlling spin polarization, optical response, and edge-state conduction in two-dimensional SnO-basednanostructures.2. Computational methodsFirst-principles calculations were performed within the frame-work of density functional theory (DFT) using the Vienna abinitio simulation package (VASP).23,24 The projector augmented-wave (PAW) method was employed to describe the interactionbetween valence electrons and ionic cores.25,26 Electronexchange and correlation were treated within the generalizedgradient approximation (GGA) using the Perdew–Burke–Ern-zerhof (PBE) functional.27 A plane-wave basis set with an energycutoff of 500 eV was adopted, which was conrmed to besufficient to ensure convergence of total energies and electronic4102 | Nanoscale Adv., 2026, 8, 4101–4108structures. Brillouin-zone (BZ) integrations were carried outusing Monkhorst–Pack k-point meshes.28 For 2D SnO mono-layers, a G-centered mesh of 20 × 20 × 1 was employed, whiledenser one-dimensional k-point sampling was used along theperiodic direction of SnO nanoribbons. A vacuum region of atleast 15 Å was introduced to eliminate spurious interactionsbetween periodically repeated images. All atomic structureswere fully relaxed until the residual Hellmann–Feynman forceson each atom were less than 0.01 eV Å−1 and the total energychange between successive ionic steps was below 10−6 eV. Spin-polarized calculations were performed for transition-metal-doped systems. The electronic density of states and bandstructures were analyzed using the vaspkit package.29 On-siteCoulomb interaction for the Co d orbitals was included withinthe DFT+U framework.30To cross-check selected electronic and optical properties,additional calculations were performed using the quantumespresso (QE) package.31,32 Norm-conserving pseudopotentialswere adopted as provided in the standard QE pseudopotentiallibraries.The frequency-dependent optical properties were evaluatedfrom the complex dielectric function 3(u) = 31(u) + i32(u) ob-tained within the linear response formalism.33–36 The opticalconductivity s(u) was calculated using the SI-unit relations(u) = 30u32(u), (1)where u is the photon angular frequency and 30 is the vacuumpermittivity. Other optical quantities, including the refractiveindex n(u), extinction coefficient k(u), absorption coefficienta(u), and energy-loss function L(u), were derived from 31(u) and32(u).3. Results and discussion3.1. Transition metal dopingDoping with transition-metal elements is a widely exploredstrategy for introducing spin polarization and magnetic func-tionality into semiconductors and oxides. In particular, dilutemagnetic oxides have attracted sustained interest as potentialbuilding blocks for spintronic devices.37 In the case of mono-layer SnO, substitutional incorporation of 3d TMs such as Co,Fe, Mn, or W provides an effective means to modify the elec-tronic structure by introducing localized impurity states withinthe band gap and inducing spin polarization.15,38–41 Fig. 1(a) and(b) present the top and side views, respectively, of the TM-dopedSnO monolayer. In this work, we consider a 4 × 4 × 1 supercellof the SnO monolayer, where a TM atom substitutes a Sn atom(blue-colored atom). Fig. 1(c)–(f) show the total density of states(DOS) and projected density of states (PDOS) for Mn-, Fe-, W-,and Co-doped SnO monolayers, respectively, calculated usingthe DFT-PBE method. Since all doped systems become spin-polarized aer TM substitution, the spin-up and spin-downDOS are plotted separately.In all cases, impurity-derived states emerge near the Fermilevel and exhibit pronounced spin asymmetry. The PDOSanalysis reveals that these impurity states mainly originate from© 2026 The Author(s). Published by the Royal Society of ChemistryFig. 1 (a) and (b) Optimized top and side views of monolayer SnO structures doped with transition metals (TMs) in a 4 × 4 × 1 supercell, whereone Sn atom is substituted by a TM atom (Mn, Fe, W, or Co). (c)–(f) Spin-resolved total density of states and projected density of states (PDOS) forMn-, Fe-, W-, and Co-doped SnO, respectively. Different color lines are showing contributions from TM d orbitals. Among the considereddopants, Co doping exhibits the strongest spin asymmetry near the Fermi level (EF), with a spin-selective electronic structure. (g) Spin-densityplot of the Co-doped SnO monolayer. The isosurface value is set to 0.001e Å−3.Paper Nanoscale Advancesthe d-orbitals of the dopant atoms. For Co-doped SnO, the PDOSindicates that the spin-up channel crosses the Fermi level,whereas the spin-down channel remains gapped, suggesting anapparent half-metallic electronic structure within the DFT-PBEapproximation.13,42 This behavior originates from stronghybridization between Co 3d and O 2p orbitals, which gives riseto spin-polarized mid-gap states. In Fig. 1(g), we present thespin-density distribution of the Co-doped SnO monolayer(SnO@Co). The spin density is primarily localized around theCo atom and partially distributed over the neighboring Oatoms, indicating hybridization between Co 3d and O 2porbitals. Table 1 summarizes the magnetic moments of thedopant atoms and their neighboring O atoms in the TM-dopedSnO monolayers. The magnitude of the magnetic momentstrongly depends on the degree of hybridization between thedopant d-orbitals and the neighboring O atoms.Thus, our PDOS analysis within the DFT-PBE approximationsuggests that the Co-doped SnO monolayer exhibits half-metallic behavior. However, most previous theoretical studieshave primarily focused on DOS/PDOS analysis, while the cor-responding band dispersion has remained largelyunexplored.16–19 Since the localized nature of impurity-inducedTable 1 Calculated local magnetic moment (in units of mB) of thedopant atom and neighboring O atoms. The notations of O atoms areindicated in Fig. 1(g)System TM atom O-1 O-2 O-3 O-4SnO@Mn 4.300 0.031 0.031 0.031 0.031SnO@Fe 3.498 0.064 0.064 0.064 0.064SnO@W 1.524 0.019 0.019 0.019 0.019SnO@Co 0.967 0.004 0.004 0.004 0.004© 2026 The Author(s). Published by the Royal Society of Chemistrystates plays a crucial role in determining the electronic andmagnetic properties of the system, we further investigate theelectronic structure through spin-resolved band structurecalculations.As a representative example, we focus on the Co-doped SnOmonolayer (SnO@Co), which shows apparent half-metallicitywithin DFT-PBE. Fig. 2(a) presents the spin-polarized elec-tronic band structure of SnO@Co, where the red and blue bandscorrespond to the spin-up and spin-down channels, respec-tively. Notably, the bands appearing near the Fermi level arenearly dispersionless (at) throughout the BZ. The absence ofsignicant band dispersion indicates strong localization of theimpurity-induced states around the Co atom, consistent withFig. 2 Electronic band structure of the Co doped SnO monolayer (a)without U (i.e., U = 0 eV) and (b) with U = 3 eV. Red and blue bandsrepresent up-spin and down-spin bands, respectively. The BZ is shownby the square. (c) Calculated optical conductivity spectra s(u) ofpristine and Co-doped SnO, derived from the imaginary part of thedielectric function 32(u) according to eqn (1).Nanoscale Adv., 2026, 8, 4101–4108 | 4103Nanoscale Advances Paperthe spin-density distribution shown in Fig. 1(g). Consequently,charge transport associated with these states is expected to benegligible due to their vanishing group velocity.To further examine correlation effects, we performed DFT+Ucalculations and present the corresponding band structure forU = 3 eV in Fig. 2(b) (results for other U values are provided inthe SI, see Fig. S1). The inclusion of on-site Coulomb interactionleads to a correlation-driven splitting of the at bands near theFermi level, resulting in the destruction of the half-metalliccharacter predicted by standard DFT-PBE. Note that we alsovaried the on-site Coulomb interaction parameter U from 1 to2 eV (see Fig. S1). In both cases, the half-metallic characterdisappears; however, the overall nature of the band structureremains qualitatively similar to that obtained for U = 3 eV.These results demonstrate that the magnetic impurity states arehighly localized and non-itinerant in nature, implying negli-gible electronic transport through these states.The non-itinerant nature of the electronic states near theFermi level is further conrmed by the optical conductivity ofthe Co-doped SnO system. Fig. 2(c) shows the calculated opticalconductivity, s(u), for pristine and Co-doped SnOmonolayers. Aclear redshi of the absorption edge is observed in the Co-doped system, indicating the onset of optical absorption atlower photon energies due to the impurity-induced states nearthe Fermi level.1,43,44 However, the magnitude of the opticalconductivity is reduced compared to that of the pristine SnOmonolayer. This suppressed optical response originates fromthe highly localized and nearly dispersionless nature of the Co-induced electronic states, which possess negligible carriermobility. Overall, our results demonstrate that Co doping inSnO monolayers induces dilute magnetism accompanied bynon-itinerant electronic states, highlighting the importance ofFig. 3 (a) Atomic structure of a hydrogen-terminated SnO nanoribbon,spheres, respectively. (b) Calculated electronic band structure and densiarrows) near the Fermi level (EF) that are absent in the pristine monolayer.to the in-gap bands (band indices 211–212 are degenerate valence bandsstrongly localized at the ribbon edges, consistent with edge-derived elepresence of two structurally equivalent edges in the nanoribbon. The iso4104 | Nanoscale Adv., 2026, 8, 4101–4108localization and electron correlation in determining the elec-tronic and optical properties of the system.3.2. Edge states in SnO nanoribbonsFrom a technological viewpoint, it is noteworthy that state-of-the-art silicon devices have already achieved effective channelwidths of approximately 10 nm and are rapidly approaching thesingle-nanometer scale. At such dimensions, edge andboundary effects inevitably play a central role in determiningelectronic transport, rendering nanoribbon models particularlyrelevant for exploring intrinsic low-dimensional physics.45To examine how edge structures inuence the electronicproperties of SnO, we constructed hydrogen-terminated SnOnanoribbons and carried out rst-principles DFT calculations.While edge-induced electronic states are well established inlow-dimensional lattice systems, as originally revealed in earlytheoretical studies and later elaborated by rst-principlescalculations,46,47 their manifestation in square-lattice oxidenanoribbons such as SnO remains largely unexplored. Fig. 3(a)displays the atomic geometry, electronic band structure, andwavefunction distributions for a representative SnO nano-ribbon. Although hydrogen passivation is introduced primarilyto eliminate dangling-bond artifacts, the edge-localized statespersist even aer passivation. Their energetic positions andspatial distributions are modied depending on the specicedge chemistry, indicating that these states are intrinsicfeatures of the ribbon geometry rather than passivation-induced states.47To evaluate the relative stability of different edge structures,we considered three passivation schemes: (i) without hydrogentermination, (ii) hydrogen bonded only to Sn atoms, and (iii)hydrogen bonded to both Sn and O atoms. The correspondingrelative total energies were calculated using QE and arewhere Sn, O, and H atoms are represented by purple, red, and whitety of states (DOS), showing additional in-gap bands (shown by the red(c) and (d) Real-space isosurfaces of the wavefunctions correspondingand 213–214 are degenerate conduction bands). The charge density isctronic states. Each in-gap band is doubly degenerate, reflecting thesurface value is set to 0.001e Å−3.© 2026 The Author(s). Published by the Royal Society of ChemistryTable 2 Relative total energies of hydrogen-terminated SnO nano-ribbons with different edge configurations. Energies are given persupercell and referenced to the unpassivated ribbon. The values arerounded to two decimal placesTermination Relative energy (eV)Without H 0.00Sn–H −16.26Sn–H–O −34.54Paper Nanoscale Advancessummarized in Table 2. Such energetic comparisons arecommonly employed to evaluate the stability of low-dimensional edge-terminated nanostructures.48 Among thethree congurations, the fully hydrogen-passivated Sn–H–Oedge is the most stable, being lower in energy by 34.54 eV persupercell than the unpassivated edge. The Sn–H terminatedconguration is also stabilized by 16.26 eV per supercell. Theseresults indicate that complete hydrogen passivation is ener-getically favorable and provides a realistic structural model forinvestigating the intrinsic edge states of SnO nanoribbons.In Fig. 3(b), we present the band structure and DOS of SnOnanoribbons. From the band structure, additional bands(marked by the red arrow) appear in the vicinity of the Fermilevel, which are absent in the pristine monolayer. The corre-sponding wavefunction isosurfaces in Fig. 3(c) and (d) demon-strate that these states are strongly conned to the Sn- and O-terminated ribbon edges. Each in-gap band is doubly degen-erate (see the band index), reecting the presence of twoequivalent edges. Such strong localization suggests that theedge states can function as one-dimensional conductive chan-nels running along the ribbon boundaries.9,10 Furthermore, weconrm that these edge states are largely independent of theribbon width. To verify this behavior, we investigated width-dependent electronic structures of SnO nanoribbons withboth larger and smaller widths compared to the ribbon shownin Fig. 3(a). The corresponding results are presented in Fig. S2in the SI. In all cases, edge-localized states persist, while onlythe band gap changes with ribbon width. These resultsdemonstrate that the emergence of edge states is an intrinsicfeature of the SnO nanoribbon geometry and is robust againstvariations in ribbon width.Importantly, the edge states appear for all edge terminationtypes, demonstrating that they are intrinsic electronic featuresof SnO nanoribbons rather than artifacts of surface chemistry.Such sensitivity to local coordination and defect chemistry isa characteristic feature of oxide semiconductors in general. Inexperimental oxide systems, including In2O3-based thin-lmtransistors, transport properties have been shown to dependcritically on oxygen vacancy concentration and local bondingenvironments.9,11 Their energetic tunability through edgepassivation indicates that the electronic structure of the ribbonboundaries can be systematically controlled, providing a prac-tical route for engineering edge-dominated conduction chan-nels in low-dimensional oxide nanostructures.49© 2026 The Author(s). Published by the Royal Society of Chemistry3.3. Chiral edge effectsTo further clarify how edge geometry inuences the electronicproperties of SnO, we constructed nanoribbons oriented alonga low-symmetry (45°) direction with respect to the underlyingsquare lattice. This chiral orientation corresponds to a cuttingdirection that is not aligned with the principal crystallographicaxes, leading to atomic edge congurations that are not relatedby mirror or rotational symmetry. As a result, the two ribbonedges become chemically and structurally inequivalent, givingrise to distinct electronic environments. As shown inFig. 4(a)–(c), three representative edge terminations wereexamined: (i) oxygen-terminated edges (O–O), (ii) tin-terminated edges (Sn–Sn), and (iii) mixed tin–oxygen termina-tion (Sn–O). All structures were hydrogen-passivated using themost stable scheme identied previously.DFT calculations reveal that all three chiral SnO nano-ribbons host edge-derived electronic states within the funda-mental band gap. The nature of these states depends stronglyon the edge composition: the O–O terminated ribbon [Fig. 4(d)]remains semiconducting, whereas the Sn–Sn and Sn–O termi-nations [Fig. 4(e) and (f)] exhibit metallic behaviour, with edgestates intersecting the Fermi level. We analyze the contributionsof edge and bulk atoms through PDOS calculations, where theblue and red curves represent the edge and bulk atom contri-butions, respectively. For all three edge congurations, theelectronic states near the Fermi level are found to originatepredominantly from the edge atoms, as clearly shown in thezoomed-in views of the DOS plots. This conrms the edge-localized nature of the states appearing around the Fermienergy. Such termination-dependent emergence of edge-localized bands is a general feature of oxide nanoribbons, inwhich reduced coordination and edge chemistry govern boththe electronic structure and stability.49–51Wavefunction isosurfaces plotted [see Fig. 4(g)–(i)] beneatheach band structure conrm the strong spatial localization ofthese states at the ribbon boundaries. While the O–O termina-tion yields localized in-gap states that do not contribute toconduction, Sn-containing edges support boundary states thatextend along the ribbon direction, consistent with one-dimensional metallic channels. Furthermore, we plot thecharge density distributions for the three types of edge nano-ribbons in Fig. S3. The charge density analysis reveals that theSn-terminated edge forms a delocalized charge channel alongthe Sn atoms, which gives rise to the metallic nature of the Sn-edge SnO nanoribbon.To assess the relative stability of the three congurations,relative energies were computed. The relative energies of the O–O, Sn–Sn, and Sn–O terminated ribbons are −5.48 eV, −4.92 eV,and −5.17 eV per unit cell, respectively. The results show thatthe O–O terminated ribbon has the lowest formation energy,making it the most stable among the three. Although the Sn–Snand Sn–O terminations exhibit metallic edge conduction, the O-rich conguration is energetically more stable.The enhanced stability of the O–O terminated edge can beattributed to the effective saturation of dangling bonds and theresulting suppression of localized high-energy states at theNanoscale Adv., 2026, 8, 4101–4108 | 4105Fig. 4 (a)–(c) Atomic structures of hydrogen-passivated SnO nanoribbons oriented along a low-symmetry (45°) direction with respect to thesquare lattice. The three edge terminations considered are (a) O–O, (b) Sn–Sn, and (c) Sn–O, which give rise to chemically and structurallyinequivalent ribbon edges. (d)–(f) Corresponding electronic band structures and densities of states (DOS). For the O–O terminated ribbon, edge-derived states remain localized within the band gap without crossing the Fermi level, preserving semiconducting behavior. In contrast, the Sn–Snand Sn–O terminated ribbons exhibit metallic edge states that intersect the Fermi level, indicating the formation of one-dimensional conductingchannels. In DOS plots, the red line and blue line show bulk and edge atoms contributions. The zoomed-in view is shown in the inset. (g)–(i) Real-space wavefunction isosurfaces shown below each panel confirm strong localization of these states at the ribbon edges. The wavefunctions areevaluated at k-points located at the midpoint between G and Y for all three ribbon configurations. The two colors represent opposite phases ofthe wavefunction, with yellow and cyan corresponding to positive and negative signs, respectively.Nanoscale Advances Paperboundary. Such a strong correlation between defect passivation,local coordination, and electronic transport is a recurringtheme in oxide semiconductors, where the balance betweenstructural stability and carrier delocalization critically governsdevice performance.5,12 In contrast, Sn-rich edges inherentlyretain partially lled Sn-derived orbitals, which promotemetallic edge conduction but incur a higher energetic cost. Thistrade-off between structural stability and electronic conductivityhighlights a general design principle for square-lattice oxidenanoribbons: oxygen-rich terminations favor thermodynamicstability, whereas cation-rich edges enable low-dimensionalmetallic transport.These results reveal a clear trade-off between structuralstability and electronic conductivity in SnO nanoribbons.Oxygen-rich edge terminations effectively saturate danglingbonds and thus minimize high-energy localized states, leadingto enhanced thermodynamic stability. In contrast, tin-richedges inherently retain partially lled Sn-derived orbitals,which promote metallic edge conduction at the cost of higherformation energies. Such a balance between energetic stabilityand low-dimensional conductivity reects a general design4106 | Nanoscale Adv., 2026, 8, 4101–4108principle in low-dimensional oxide systems, where local coor-dination and defect chemistry play decisive roles in deter-mining electronic functionality.52 Accordingly, chiral edgeengineering combined with controlled edge passivationprovides a viable route for tailoring the electronic properties ofSnO nanoribbons.4. ConclusionIn conclusion, we have systematically investigated the elec-tronic, magnetic, and optical properties of monolayer SnOthrough transition-metal doping and edge engineering usingrst-principles calculations. Substitutional Co doping intro-duces strongly spin-polarized impurity states near the Fermilevel, giving rise to an apparent half-metallic behavior withinthe DFT-PBE approximation. However, upon inclusion of on-site Coulomb interaction, the half-metallic character disap-pears due to correlation-driven splitting of the localized impu-rity states. These ndings indicate that Co-doped SnO exhibitsdilute localized magnetism, highlighting its potential for oxide-based spintronic applications.© 2026 The Author(s). Published by the Royal Society of ChemistryPaper Nanoscale AdvancesWe further demonstrated that SnO nanoribbons host robustedge-localized electronic states that persist across differentedge terminations and passivation schemes, conrming theirintrinsic origin. In addition, these localized edge states arelargely independent of the ribbon width. Hydrogen passivationstabilizes the edge structures without eliminating the edgestates, providing a realistic platform for probing edge-dominated transport in oxide nanostructures. For chiral nano-ribbons oriented along low-symmetry directions, a clear trade-off emerges between thermodynamic stability and electronicconductivity: oxygen-rich edges favor structural stability,whereas tin-rich edges enable metallic one-dimensionalconduction channels.The present results also suggest that the proposed strategy ofcombining transition-metal doping and edge engineering maybe extended to other oxide semiconductors. However, theemergence of localized at-band states and edge-dependentmetallicity in SnO is strongly inuenced by its unique lone-pair-driven electronic structure arising from Sn 5s-O 2phybridization, which distinguishes it from oxide systems suchas SnO2 and In2O3. Therefore, while the general design princi-ples may be broadly applicable, the resulting electronic andmagnetic behaviors are expected to depend sensitively on theunderlying orbital characteristics of the host oxide material.These ndings establish general design principles for low-dimensional oxide semiconductors, where electronic function-ality can be tuned through a delicate interplay of dopantchemistry, local coordination, and edge composition. Thepresent work thus positions monolayer SnO as a versatile plat-form for exploring multifunctional nanoelectronic and spin-tronic phenomena in oxide-based two-dimensional materials.Conflicts of interestThere are no conicts to declare.Data availabilityAll relevant data supporting the ndings of this study areincluded in the article and its supplementary information (SI).Additional data or computational les are available from thecorresponding author upon reasonable request. Supplementaryinformation: additional computational details, electronicstructures, spin-density distributions, and supporting data. SeeDOI: https://doi.org/10.1039/d6na00140h.AcknowledgementsThis work was supported by JSPS KAKENHI (Grant No.JP25K01609, No. JP22H05473, No. JP21H01019, andJP26H02222) and JST CREST (Grant No. JPMJCR19T1). K.W.acknowledges the nancial support for Basic Science ResearchProjects (Grant No. 2401203) from the Sumitomo Foundation.© 2026 The Author(s). Published by the Royal Society of ChemistryReferences1 E. Fortunato, P. Barquinha and R. Martins, Adv. Mater., 2012,24, 2945.2 T. Kamiya, K. Nomura and H. Hosono, Sci. Technol. Adv.Mater., 2010, 11, 044305.3 H. Hosono, J. Non-Cryst. Solids, 2006, 352, 851.4 Z. Zhang, Y. Guo and J. Robertson, Chem. Mater., 2022, 34,643.5 Z. Wang, P. K. Nayak, J. A. Caraveo-Frescas andH. N. Alshareef, Adv. Mater., 2016, 28, 3831.6 J. Du, C. Xia, Y. Liu, X. Li, Y. Peng and S. Wei, Appl. Surf. Sci.,2017, 401, 114.7 A. Shukla and N. 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Published by the Royal Society of Chemistry Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO Dilute magnetism and edge-state engineering in monolayer SnO