Au Substrate Research Articles

Highly Selective On‐Surface Dehydrogenative Aromatization of n‐Hexyl to Phenyl Substituents

Dehydrogenative aromatization of alkyl substituents represents a powerful approach to aryl‐substituted functional molecules. However, the inertness of alkyl groups and the need for harsh reaction conditions accompanied by low product selectivity hamper its widespread applications. Here, we demonstrate the highly selective on‐surface thermal aromatization of n‐hexyl substituents on polycyclic aromatic hydrocarbons (PAHs) to their phenyl‐substituted analogues under mild conditions. After depositing two representative precursor molecules, n‐hexyl‐substituted hexaphenylbenzene (HPB‐Hex) and bianthryl octacarboxylic tetraimide (BATI‐Hex), onto a pre‐heated Au(111) substrate, dehydroaromatization of the peripheral n‐hexyl groups into phenyl rings occurs, following the planarization of hexaphenylbenzene and bianthryl core. This process involves sequential intramolecular C‐C bond rotations, dehydrogenation, and cyclodehydrogenation reactions, yielding phenyl‐substituted hexabenzocoronene (HBC‐Ph) and bisanthene octacarboxylic tetraimides (BSTI‐Ph). The reaction sequences were monitored using scanning tunneling microscopy (STM) and bond‐resolved non‐contact atomic force microscopy (nc‐AFM), offering structural proof of both intermediates and final products. These experimental techniques were complemented by density functional theory (DFT) simulations, which facilitated the detection of crucial steps in the conversion of n‐hexyl to phenyl groups. Moreover, the effect of alkyl aromatization on the electronic properties of the newly formed aromatic hydrocarbons was elucidated using scanning tunneling spectroscopy (STS).

Highly Selective On‐Surface Dehydrogenative Aromatization of n‐Hexyl to Phenyl Substituents

Dehydrogenative aromatization of alkyl substituents represents a powerful approach to aryl‐substituted functional molecules. However, the inertness of alkyl groups and the need for harsh reaction conditions accompanied by low product selectivity hamper its widespread applications. Here, we demonstrate the highly selective on‐surface thermal aromatization of n‐hexyl substituents on polycyclic aromatic hydrocarbons (PAHs) to their phenyl‐substituted analogues under mild conditions. After depositing two representative precursor molecules, n‐hexyl‐substituted hexaphenylbenzene (HPB‐Hex) and bianthryl octacarboxylic tetraimide (BATI‐Hex), onto a pre‐heated Au(111) substrate, dehydroaromatization of the peripheral n‐hexyl groups into phenyl rings occurs, following the planarization of hexaphenylbenzene and bianthryl core. This process involves sequential intramolecular C‐C bond rotations, dehydrogenation, and cyclodehydrogenation reactions, yielding phenyl‐substituted hexabenzocoronene (HBC‐Ph) and bisanthene octacarboxylic tetraimides (BSTI‐Ph). The reaction sequences were monitored using scanning tunneling microscopy (STM) and bond‐resolved non‐contact atomic force microscopy (nc‐AFM), offering structural proof of both intermediates and final products. These experimental techniques were complemented by density functional theory (DFT) simulations, which facilitated the detection of crucial steps in the conversion of n‐hexyl to phenyl groups. Moreover, the effect of alkyl aromatization on the electronic properties of the newly formed aromatic hydrocarbons was elucidated using scanning tunneling spectroscopy (STS).

Electron Transfer Capability in Atomic Hydrogen Reactions for Imidazole Groups Bound to the Insulating Alkanethiolate Layer on Au(111).

The charge transfer capability associated with chemical reactions at metal-organic interfaces was studied via the atomic H addition reaction for an imidazole-terminated alkanethiolate self-assembled monolayer (Im-SAM) film on Au(111) at room temperature, using near-edge X-ray absorption fine structure spectroscopy, infrared reflection absorption spectroscopy, work function measurements, and density functional theory calculations. The imidazolium cation is a stable species in liquids; therefore, it is pertinent to determine whether the hydrogenation reactions of the imidazole groups produce imidazolium cations accompanied by electron transfer to the Au substrate, even in the absence of solvate and/or counterions on the insulating alkanethiolate layer. The experiments made it clear that the imidazolium moieties were formed during the irradiation of Im-SAM with atomic H. Theoretical model calculations also revealed that the total energies and molecular orbital levels satisfied the imidazolium cation formation associated with electron transfer. In a detailed analysis of the work function change depending on H irradiation, we confirmed that some of the imidazolium radicals became cations in Im-SAM.

Chirality and Local Electron Density of States in a Two-Dimensional Molecular Crystal Self-Assembled by Prochiral Radical Molecules.

Creating and unveiling chiral systems is important to the development of new materials and devices. In this study, after depositing prochiral radical molecule 3-carbamoyl-2,2,5,5-tetramethyl pyrroline-1-oxyl (CTPO) on a Au(111) substrate, 2D molecular crystals with two chiralities of CTPO molecules have been discovered. A single CTPO molecule is an achiral molecule in three-dimensional space, and it can form chiral configurations after adsorbing on the substrate. The chiralities of 2D molecular crystals originate from the chiral properties of adsorbed CTPO molecules and their assembling. Molecules with different chiralities are connected with molecular recognition through hydrogen bond interactions. Through density functional theory simulations, the hydrogen bond networks and molecular structures of this system were explored. To gain a further understanding of this system, the electronic property of CTPO/Au(111) was studied with a local density of states (LDOS) characterization. A peculiar LDOS distribution related to the vibrational excitation of the molecules was mapped at the submolecular scale. These results are useful for understanding the nature of chirality formation, 2D molecular crystal construction, and radical molecule applications.

Quasi-one-dimensional bismuth chains with topological properties

One-dimensional (1D) systems have received a lot of attention due to their exotic physical phenomena such as quantization of conductance, Peierls instability, and Luttinger liquid behavior. Here, we present the synthesis of self-assembled quasi-1D bismuth (Bi) chains on an Au(111) substrate, highlighting their topological properties. Scanning tunneling microscopy and spectroscopy measurements reveal that the high-quality large area array is composed of Bi atomic chains with a bandgap of 0.5 eV. Density functional theory (DFT) calculations confirm the experimental observation and reveal the topological properties of the system, providing evidence of the spin texture of the Bi atomic chains. Our DFT results predict that a single Bi chain hosts exotic topological properties. The atomically precise synthesis of Bi atomic chains overcomes the limitation of the top-down approach toward integration of devices. The work sheds light on the realization of 1D system, providing a platform for further investigation into the intriguing physics in 1D systems.

Strongly Enhanced Electronic Bandstructure Renormalization by Light in Nanoscale Strained Regions of Monolayer MoS2/Au(111) Heterostructures.

Understanding and controlling the photoexcited quasiparticle (QP) dynamics in monolayer (ML) transition metal dichalcogenides (TMDs) lays the foundation for exploring the strongly interacting, nonequilibrium two-dimensional (2D) QP and polaritonic states in these quantum materials and for harnessing the properties emerging from these states for optoelectronic applications. In this study, scanning tunneling microscopy/spectroscopy (STM/scanning tunneling spectroscopy) with light illumination at the tunneling junction is performed to investigate the QP dynamics in ML MoS2 on an Au(111) substrate with nanoscale corrugations. The corrugations on the surface of the substrate induce nanoscale local strain in the overlaying ML MoS2 single crystal, which result in energetically favorable spatial regions where photoexcited QPs, including excitons, trions, and electron-hole plasmas, accumulate. These strained regions exhibit pronounced electronic bandstructure renormalization as a function of the photoexcitation wavelength and intensity as well as the strain gradient, implying strong interplay among nanoscale structures, strain, and photoexcited QPs. In conjunction with the experimental work, we construct a theoretical framework that integrates nonuniform nanoscale strain into the electronic bandstructure of a ML MoS2 lattice using a tight-binding approach combined with first-principle calculations. This methodology enables better understanding of the experimental observation of photoexcited QP localization in the nanoscale strain-modulated electronic bandstructure landscape. Our findings illustrate the feasibility of utilizing nanoscale architectures and optical excitations to manipulate the local electronic bandstructure of ML TMDs and to enhance the many-body interactions of excitons, which is promising for the development of nanoscale energy-adjustable optoelectronic and photonic technologies, including quantum emitters and solid-state quantum simulators for interacting exciton polaritons based on engineered periodic nanoscale trapping potentials.

Optical Extinction-Based 3D Nano-Imaging of WS2 on Gold.

Broadband nanoextinction images recorded in tip-enhanced optical spectroscopy geometry track the 3D topography of a single layer of WS2 on Au substrate. The described nano-optical method is complementary to conventional atomic force microscopy and offers additional information about the buried material-metal interface that is not accessible using conventional topographic imaging. Beyond 3D optical imaging, we observe large variations in the junction plasmon resonance on the nanoscale. The latter is important to understand and account for in tip-enhanced Raman and photoluminescence studies that target low-dimensional materials specifically. Our observations and (coherent) optical scattering-based method are also relevant to emerging efforts aimed at exploring strong coupling and Fano interferences in hybrid plasmonic-low dimensional quantum material systems.

Tuning the Spin Interaction in Nonplanar Organic Diradicals through Mechanical Manipulation.

Open-shell polycyclic aromatic hydrocarbons (PAHs) represent promising building blocks for carbon-based functional magnetic materials. Their magnetic properties stem from the presence of unpaired electrons localized in radical states of π character. Consequently, these materials are inclined to exhibit spin delocalization, form extended collective states, and respond to the flexibility of the molecular backbones. However, they are also highly reactive, requiring structural strategies to protect the radical states from reacting with the environment. Here, we demonstrate that the open-shell ground state of the diradical 2-OS survives on a Au(111) substrate as a global singlet formed by two unpaired electrons with antiparallel spins coupled through a conformational-dependent interaction. The 2-OS molecule is a "protected" derivative of the Chichibabin's diradical, featuring a nonplanar geometry that destabilizes the closed-shell quinoidal structure. Using scanning tunneling microscopy (STM), we localized the two interacting spins at the molecular edges, and detected an excited triplet state a few millielectronvolts above the singlet ground state. Mean-field Hubbard simulations reveal that the exchange coupling between the two spins strongly depends on the torsional angles between the different molecular moieties, suggesting the possibility of influencing the molecule's magnetic state through structural changes. This was demonstrated here using the STM tip to manipulate the molecular conformation, while simultaneously detecting changes in the spin excitation spectrum. Our work suggests the potential of these PAHs as all-carbon spin-crossover materials.

Epitaxial Growth of Monolayer WS2 Single Crystals on Au(111) Toward Direct Surface-Enhanced Raman Spectroscopy Detection.

The epitaxial growth of wafer-scale two-dimensional (2D) semiconducting transition metal dichalcogenides (STMDCs) single crystals is the key premise for their applications in next-generation electronics. Despite significant advancements, some fundamental factors affecting the epitaxy growth have not been fully uncovered, e.g., interface coupling strength, adlayer-substrate lattice matching, substrate step-edge-guiding effects, etc. Herein, we develop a model system to tackle these issues concurrently, and realize the epitaxial growth of wafer-scale monolayer tungsten disulfide (WS2) single crystals on the Au(111) substrate. This epitaxial system is featured with good adlayer-substrate lattice matching, obvious step-edge-guiding effect for the unidirectionally aligned nucleation/growth, and relatively weaker interfacial interaction than that of monolayer MoS2/Au(111), as evidenced by the evolution of a uniform Moiré pattern and an intrinsic band gap, according to on-site scanning tunneling microscopy/spectroscopy (STM/STS) characterizations and density functional theory calculations. Intriguingly, the unidirectionally aligned monolayer WS2 domains along the Au(111) steps can behave as ultrasensitive templates for surface-enhanced Raman scattering detection of organic molecules, due to the obvious charge transfer occurred at substrate step edges. This work should hereby deepen our understanding of the epitaxy mechanism of 2D STMDCs on single-crystal substrates, and propel their wafer-scale production and applications in various cutting-edge fields.

Realization of Material with an Atomic Ruby Lattice.

The ruby lattice is one of the tight-binding models which hosts a flat band in its electronic structure and has potential applications in future spintronics and quantum devices. However, the experimental realization of a ruby lattice in realistic materials remains elusive. Here, we have experimentally realized an atomic ruby lattice by fabricating monolayer CuCl1+x on a Au(111) substrate. Scanning tunneling microscopy/spectra (STM/STS) measurements combined with density-functional theory (DFT) calculations reveal that the Cu atoms are arranged in a ruby lattice in this monolayer. Moreover, a significant density of states (DOS) peak corresponding to the characteristic of a ruby system is observed, consistent with both the tight-binding model and first-principles calculations on the band structure. Our work provides a promising platform to explore the physics of the ruby model.

New Electrochemical Approach for Synthesis of Nanoporous Silver

Cu-Ag alloy films were electrodeposited on Au substrates to serve as precursor alloys for synthesizing finely-structured nanoporous Ag (NPS) structures. Two innovative approaches, surface limited redox replacement (SLRR) and defect mediated growth (DMG) along with overpotential deposition (OPD), were comparatively utilized to fabricate Cu-Ag alloy films. The electrolyte for these novel approaches contained Pb2+ ions to serve either as a sacrificial metal to be replaced by the co-depositing Cu and Ag (in SLRR) or as mediating metal to facilitate the 2D growth of both alloy constituents (in DMG). The resulting alloy films from both approaches displayed superior uniformity and miscibility compared to the OPD alloy, as evidenced by electrochemical scanning electron microscopy (SEM) and X-ray diffraction characterization routines. In a subsequent step, NPS structures were generated through the de-alloying of as-deposited Cu-Ag alloys, as illustrated by SEM imaging that revealed ligament and pore sizes with a thickness in the ballpark of 40 nm. Also, surface area measurements done by a Pb underpotential deposition assay suggested a surface enhancement ratio nearly five times higher than that of flat Ag. Furthermore, various de-alloying potentials were assessed to determine the optimal de-alloying potential for the best outcome of the de-alloying process.

Effects of multilayer MoS2 coating on the mechanical properties of metals: A competition between external force and interfacial adhesion

Molybdenum disulfide (MoS2) is a two-dimensional material that exhibits unique interfacial interactions with metals, making it potential coating material for improving material properties of metals. In this work, the effects of multilayer MoS2 coating on the mechanical properties and deformation behaviours of copper (Cu) and gold (Au) substrates are investigated by nanoindentation experiments and molecular dynamics (MD) simulations. Specifically, our experimental results indicate that the MoS2 coating greatly increases the Young's modulus and hardness of Au substrate throughout the indentation process. In the MoS2/Cu system, however, the MoS2 coating exhibits inverse effects at diffident indentation depths, which, specifically, has the weakening and enhancing effects at the early and late stages of the indentation process, respectively. MD simulations indicate that the different effects of the MoS2 coating on the mechanical properties of Au and Cu substrates are attributed to the different interfacial adhesion properties between the MoS2/Cu and MoS2/Au systems, as the binding energy of the MoS2/Au system is much larger than that of its MoS2/Cu counterpart. Moreover, it is also revealed in MD simulations that the load-bearing area of metal substrates can be significantly enlarged by the MoS2 coating, which leads to the dense dislocations distributed in metal substrates and thus the strain-hardening in MoS2/metal composites.

Electrodeposition of Bi2Se3 on conductive substrates: Influence of electrolyte temperature on morphology, crystalline structure, and optical properties

Bismuth selenide (Bi2Se3) is a semiconductor of great interest for application in energy conversion systems. In this work, the impact of electrolyte temperature on the morphology, crystalline structure, and optical properties of electrodeposited Bi2Se3 films was studied on several conductive substrates. The layers were grown by potentiostatic deposition with electrolytes at 25 °C (RT) and 60 °C on Cr, ITO, and Au substrates. The SEM analyses show that compact and smooth films are obtained when the electrolyte is heated, whereas rough layers are formed at RT depositions. The XRD measurements indicated that the growth depends on substrates and electrolyte temperature, with the samples grown over Au demonstrating a higher crystalline quality. TEM analyses revealed nanostructured regions with monocrystalline SAED patterns are formed when the films are grown on Au at RT, while for the same substrate the depositions with electrolyte at 60 °C result in regions with a polycrystalline nature. The optical characteristics revealed bandgap values close to 1.50 eV that are obtained by adjusting the electrodeposition conditions.

Understanding the morphology and chemical activity of model ZrOx/Au (111) catalysts for CO2 hydrogenation

In this study, the growth of ZrOx on Au (111) was investigated using scanning tunneling microscopy (STM) and synchrotron-based ambient pressure X-ray photoelectron spectroscopy (AP-XPS). Nanostructures of ZrOx (x = 1,2) at the sub-monolayer (≤ 0.3 ML) level were prepared by vapor depositing Zr metal onto Au (111) followed by oxidation with O2 or CO2. At low coverages of the admetal (< 0.05 ML), the formed ZrOx nanostructures were dispersed randomly on the terraces and steps of the Au(111) substrate. Strong oxide-metal interactions prevented the formation of islands of zirconia. The ZrOx nanostructures displayed a reactivity towards CO2 and H2 not seen for bulk zirconia. C 1 s AP-XPS results indicated that CO2 molecules adsorbed on Zr/ZrOx/Au(111) surfaces could undergo partial decomposition on Zr (CO2, gas → COgas + Oads), or react with oxygen sites from ZrOx to yield carbonates (Zr-CO3, ads). After exposing ZrO2/Au (111) surfaces to 1:3 mixtures of CO2:H2, the formation of HCOO, CO3, and CH3O was detected in AP-XP spectra. These chemical species decomposed at temperatures in the range of 400‒600 K, making them possible reaction intermediates for methanol synthesis.

Janus Doping of Sulfur into Platinum Diselenide Ribbons.

2D platinum diselenide (PtSe2), a novel member of the transition metal dichalcogenides (TMDCs) family, possesses many excellent properties, including a layer-dependent bandgap, high carrier mobility, and broadband response, making it promise for applications in technologies like field-effect transistors and room-temperature photodetectors. Doping represents an effective method to modify the electrical properties of 2D TMDCs and to bestow upon them additional functions. However, to date, little research has been conducted on the successful doping of 2D PtSe2 for modification. In this study, sulfur (S) powder is utilized during the chemical vapor deposition growth process of 2D PtSe2 ribbons and successfully integrated into the PtSe2 lattice through substitutional doping. The Au substrate significantly decreases the substitution energy of Se atoms in the lower layer of PtSe2, resulting in the formation of the Janus PtSSe structure. S-doped PtSe2 ribbons demonstrate significant symmetry breaking and enhanced electrical properties, showcasing a strong nonlinear optical response and certain synaptic plasticity, further simulating some neuromorphological processes. This study not only demonstrates a viable method for controllable doping and modification of 2D PtSe2 but also establishes a platform for exploring the characteristics of Janus TMDCs.

The organization of pyridazine adsorbed on Au(1 1 1) electrode in sulfuric and perchloric acids – As probed by in situ STM

The adsorption of pyridazine (PD) on a gold electrode served as a model to study the orientation and arrangement of an organic adsorbate bearing a heterocyclic molecular structure at an electrified interface. Because the two N-ends of PD could interact with a Au electrode, the acid-base equilibrium of PD at an electrified interface can be different from that in a solution phase. Unprotonated and protonated PD interacted with the Au electrode differently, leading to dissimilar spatial structures on the Au(111) electrode. Moreover, having a large dipole moment of 4.22 D, PD adopted different adsorption configurations, as the Au potential was modulated. The indispensable anion present in the supporting electrolyte can compete with PD for surface sites on the Au electrode. Since the potential of a charged conductor is established by the physical contact with an electrolyte, the study of the adsorption of PD on a Au(111) electrode calls for the use of an in situ tool, such as a scanning tunneling microscope (STM), which provides sub-nanometer information of the interface in real-time and real-space. Different phases of adsorbed PD molecules on an ordered Au(111) electrode were revealed as a function of potential, pH and anion. The most notable event for PD adsorbed on Au(111) is attributed to the sharp transition from a disordered state to highly organized structures in 0.1 M H2SO4 and HClO4. The obtained STM images enabled a direct measurement of the spacing between PD admolecules, from which the molecular reorientations on the Au electrode were inferred. PD admolecules flipped from the horizontal to the upright configuration, tethered to Au substrate via the two N-ends, at positive potentials. Different ordered PD structures seen in H2SO4 and HClO4 imply anions were coadsorbed with PD molecule on the Au electrode. The acid-base equilibrium of PD at the Au electrode was examined with STM in pH 1 and 3 media.

Computational Characterization of the On-Surface Synthesis of Low-Dimensional Nanostructures

On-surface chemistry represents a fast-growing field allowing to synthesize molecular structures not available by traditional wet chemistry. In this context, high-resolution scanning probe microscopy techniques are able to provide unprecedented spatial resolution, allowing to precisely identify individual products of the reactions. Nevertheless, a deep understanding of the reaction mechanism under the conditions imposed by the substrate remains unknown.Nowadays, various computational strategies are employed to characterize the optimal reaction pathways of the chemical processes that take place on the surfaces of solids. For example, one of the most popular approaches is the nudged elastic band (NEB) as well as different transition state theory methods beyond it. These approaches had demonstrated their capability to characterize the potential energy landscape of the reaction pathways [1-2]. Another approach that had attracted the interest of the on-surface synthesis community is the application of molecular dynamics (MD) methods, within the canonical ensemble, and based on the QM/MM (quantum mechanics/molecular mechanics) of the interatomic forces [3-4]. This approach, which combines Density functional theory (DFT) and empirical force fields to describe the interaction forces, allows to simulate very large systems, at a very low computational cost while still accounting for the crucial quantum mechanics interactions. Also, such temperature-dependent simulations include the effect of entropy, vibrations modes, concerted motion, etc.I will present the experimental and computational results of different projects in which we have made use of the aforementioned computational approaches to achieve a better understanding of the on-surface synthesis experiments performed by the group. For example, the rationalization of the selective cyclodehydrogenation of non-benzenoid nanographenes deposited on a Au(111) substrate by means of temperature-dependent MD calculations and the analysis of the obtained vibrational modes (See Figure 1a). The group had also studied the stepwise transformation of coronene-based organometallic networks into two-dimensional covalent patches through intermolecular homocoupling (See Figure 1b). We had as well investigated the transformation of indenyl precursors, through a triple C-H cleavage followed by a peripheral directed homocoupling, to form a polyacetylene backboned polymer that features a parity dependent and highly delocalized soliton in-gap state (See Figure 1c).

Catalytic Potential of Supported Superatoms.

The importance of catalysts in industrial products is a driving factor in the search of efficient and cost-effective catalysts, creating considerable interest in the past decade in single-atom catalysis. One of the first requirements of a good catalyst is that it should bind to the molecules with energies intermediate between physisorption and chemisorption while simultaneously activating them. Herein, it is shown that superatoms, which are atomic clusters with fixed size and composition, can meet this challenge even better than the atoms whose chemistry they mimic. The reactions of molecules such as H2, O2, N2, CO, NO, and CO2 with an atom (Li) and its corresponding superatom (Li3O) are confirmed through study. As these clusters need to be supported on a substrate for practical applications, the study focuses on the reaction of CO2 with Li and Li3O supported on graphene, Au(111), and Cu(111) substrates. Using density functional theory, it is shown that the Li3O superatom can activate CO2 far greater than the Li atom - stretching the CO bond from 1.16 Å to as large as 1.30 Å and bending the O─C─O bond angle from 180° to as low as 120°. Equally interesting, the results are not very sensitive to the substrate.

Thermoelectric properties of monolayer GeTe with Au, Ni, and Co substrates

Since the basic thermoelectric (TE) units must be integrated on substrates to form large-scale devices, it would be more practical to study the TE properties of the TE devices with substrates. Based on the first-principles calculation and nonequilibrium Green’s function method, we comparatively investigate the TE properties of the GeTe monolayer with its leads deposited on Au, Ni, and Co substrates, which are called GeTe-X (X = Au, Ni, and Co). It is shown that in comparison with the pristine GeTe monolayer, the figures of merit ZTs of the GeTe-X are seriously changed with one ZT peak appearing near zero chemical potential. The GeTe-Au and GeTe-Ni are of higher TE performance near zero chemical potential than the GeTe-Co, indicating one can choose Au or Ni as the substrate. Moreover, we show that the TE properties of the GeTe-X are sensitively dependent on the substrate layer number, the central scattering length, and the temperature, which necessitates the synergistic optimization of the related parameters to obtain the best TE performance. This work should be an important reference for designing practical GeTe-based TE devices.

Influence of cutoff radius and tip atomic structure on energy barriers encountered during AFM tip sliding on 2D monolayers

In computational studies using the Lennard–Jones (LJ) potential, the widely adopted 2.5 σ cutoff radius effectively truncates pairwise interactions across diverse systems (Santra et al 2008 J. Chem. Phys. 129 234704, Chen and Gao 2021 Friction 9 502–12, Bolintineanu et al 2014 Part. Mech. 1 321–56, Takahiro and Kazuhiro 2010 J. Phys.: Conf. Ser. 215 012123, Zhou et al 2016 Fuel 180 718–26, Toxvaerd and Dyre 2011 J. Chem. Phys. 134 081102, Toxvaerd and Dyre 2011 J. Chem. Phys. 134 081102). Here, we assess its adequacy in determining energy barriers encountered by a Si monoatomic tip sliding on various two-dimensional (2D) monolayers, which is crucial for understanding nanoscale friction. Our findings emphasize the necessity of a cutoff radius of at least 3.5 σ to achieve energy barrier values exceeding 95% accuracy across all studied 2D monolayers. Specifically, 3.5 σ corresponds to 12.70 Å in graphene, 12.99 Å in MoS2 and 13.25 Å in MoSe2. The barrier values calculated using this cutoff support previous experiments comparing friction between different orientations of graphene and between graphene and MoS2 (Almeida et al 2016 Sci. Rep. 6 31569, Zhang et al 2014 Sci. China 57 663–7). Furthermore, we demonstrate the applicability of the 3.5 σ cutoff for graphene on an Au substrate and bilayer graphene. Additionally, we investigate how the atomic configuration of the tip influences the energy barrier, finding a nearly threefold increase in the barrier along the zigzag direction of graphene when using a Si(001) tip composed of seven Si atoms compared to a monoatomic Si tip.