arXiv subjects

Alice Cartoceti

Publications and source records attributed to Alice Cartoceti.

4 recordsLinked to original sources

arXiv2026

Multiwavelength Raman investigation of mono- and few-layer MoS2 grown by Pulsed Laser Deposition on SiO2

Molybdenum disulfide (MoS$_2$) is a semiconductor whose vibrational and excitonic properties are highly sensitive to layer number and structural disorder. We demonstrate the growth of MoS$_2$ monolayers on inert, electronics-compatible SiO$_2$ substrates using room-temperature pulsed laser deposition (PLD). Control of the process parameters enables tuning from monolayer to multilayer films, which we investigate by multiwavelength Raman spectroscopy. The evolution of the Raman-shift difference between the $E_{2g}^{1}$ and $A_{1g}$ modes, combined with an assessment of defect density, tracks film growth as a function of the number of deposition laser pulses. Although excitonic effects strongly influence the optical response of two-dimensional transition-metal dichalcogenides, experimental reports of symmetry-selective exciton-phonon coupling remain limited. We provide experimental evidence of symmetry-dependent exciton-phonon coupling in PLD-grown monolayer MoS$_2$. Specifically, we observe modulation of the resonant behaviour of the out-of-plane $A_{1g}$ and in-plane $E_{2g}^{1}$ modes, related to their different coupling to A excitons, predominantly derived from Mo $d_{z^2}$ orbitals, and C excitons, characterized by mixed orbital contributions from Mo $d_{z^2}$ and S $p_x$ and $p_y$ states. Comparison with mechanically exfoliated monolayers reveals the role of growth-induced defects in modulating these interactions. These findings establish room-temperature PLD as a viable approach for growing two-dimensional MoS$_2$ on inert, electronics-compatible substrates and provide insight into the interplay between excitonic resonances and growth-induced disorder in two-dimensional MoS$_2$.

cond-mat.mtrl-sci↗

arXiv2026

Iron-mediated on-surface synthesis of substrate-decoupled graphdiyne monolayers

Graphdiynes are emerging two-dimensional sp-sp$^2$ carbon materials with electronic structures complementing those of graphene, yet their on-surface synthesis is limited by the persistence of metalated intermediates or yields disordered covalent networks. Here, we report an iron-assisted route to covalent hydrogenated graphdiyne monolayers on Au(111) from 1,3,5-tris(bromoethynyl)benzene. Low-temperature scanning tunnelling microscopy, X-ray photoelectron spectroscopy and density functional theory show that Fe scavenges chemisorbed Br byproducts forming FeBr$_2$, in turn promoting the removal of Au adatoms from the organometallic network, thus enabling its metalated-to-covalent conversion under mild thermal treatment. Subsequent annealing removes FeBr$_2$ and yields covalent, ordered domains weakly coupled to the substrate. Scanning tunnelling spectroscopy, combined with density functional theory, reveals a semiconducting gap of about 1.6 eV associated with carbon p$_z$ frontier orbitals. This Fe-mediated on-surface synthesis strategy provides a route to atomically precise, weakly substrate-coupled graphdiyne networks and offers a design principle for two-dimensional carbon semiconductors.

cond-mat.mtrl-sci↗

arXiv2026

2D abrupt nano-junctions blending sp-sp2 bonds on atomically precise heterostructures

Two-dimensional heterostructures combining sp-sp2 hybridization,blending graphene with graphyne-based allotropes, offer substantial potential for enhancing the tunability of electronic and transport properties while providing significant structural flexibility. These attributes are desirable for next generation nanoscale electronic applications. Despite such potential, their experimental realization remains elusive, as synthesized carbon heterostructures are limited to doped, graphene-based systems exhibiting exclusively sp2 hybridization. Here, we demonstrate the on-surface synthesis of covalently bonded sp-sp2 lateral heterostructures between graphene nanoribbons and graphdiyne networks on Au(111). Atomic-resolution scanning tunnelling microscopy, combined with density functional theory, reveals the formation mechanism of the covalent interfacial bonds between nanoribbons and graphdiynes, also highlighting the key role of surface chemistry. Bromine atoms deriving from the molecules dehalogenation and chemisorbed along the nanoribbon inhibit the junction formation, but bonding efficiency can be boosted up to 71% by controlled removal of these by-products. Electronic structure and transport calculations show that the 2D heterostructure by itself is characterized by disentangled properties for the two subsystems, forming an atomically narrow junction enabling voltage-tunable spatial current separation in two dimensions. There results define a viable strategy for engineering graphene-based sp-sp2 heterostructures, paving the way for the design and synthesis of all-carbon nanoscale electronic architectures.

cond-mat.mtrl-sci↗

arXiv2025

Halogen-Terminated Carbon Atomic Wires by Laser Ablation in Halogenated Organic Solvents: Synthesis and Characterization

We report the synthesis of halogenated carbon atomic wires (halopolyynes) via pulsed laser ablation in liquid and their comprehensive Raman characterization. Using dichloromethane and dibromomethane-containing solutions, we produced polydisperse mixtures of monohalogenated (HC$_{2n}$X) and dihalogenated (XC$_{2n}$X) polyynes (X=Cl, Br; n=3-10). High-performance liquid chromatography enabled separation and analysis of these compounds, while chemical derivatization and mass spectrometry confirmed their molecular structures. A possible formation mechanism is proposed, involving carbon chain polymerization and termination by hydrogen and halogen atoms from atomized solvent molecules during the plasma phase. UV-Vis absorption and synchrotron-based UV Resonance Raman spectroscopy reveal that halogen terminations act as auxochromes through p-$\pi$ conjugation between their lone-pair electrons and the sp-carbon backbone, extending effective conjugation length. This interaction reduces bond length alternation and moderately redshifts vibronic absorption and vibrational modes. Resonance Raman spectra show selective overtone enhancement and vibrational anharmonicity consistent with carbyne-like materials. These findings expand the synthetic approaches for halogenated carbon atomic wires and establish halopolyynes as a platform for tailoring electronic and optical properties of sp-carbon wires.

physics.chem-ph↗