Enrico Gnecco

Jagiellonian University | UJ · Department of Solid State Physics

Friction control and technological advancement are intimately intertwined. Concomitantly, two-dimensional materials occupy a unique position for realizing quasi-frictionless contacts. However, the question arises of how to tune superlubric sliding. Drawing inspiration from twistronics, we propose to control superlubricity via moiré patterning. Fric...

In this work, we investigated the sliding friction measured between poly(methyl methacrylate) (PMMA) colloidal probes with two different diameters D (1.5 and 15 μm) and laser-induced periodic surface structures (LIPSS) on stainless steel with periodicities Λ of 0.42 and 0.9 μm, when the probes are elastically driven along two directions, perpendicu...

We have numerically investigated the occurrence of long slips when a point mass representing a tip of a solid surface is elastically driven on a hexagonal surface lattice along an arbitrary direction. Tip pathways and slip length histograms are estimated for different values of the damping coefficient γ defining the duration of the slip phases. The...

A combination of low temperature atomic force microcopy and molecular dynamic simulations is used to demonstrate that soft designer molecules realize a sidewinding motion when dragged over a gold surface. Exploiting their longitudinal flexibility, pyrenylene chains are indeed able to lower diffusion energy barriers via on-surface directional lockin...

Friction force microscopy (FFM) explores the interaction in a sliding contact on the nanoscale, providing information on the frictional dynamics and lateral contact stiffness with lattice resolution. Recent FFM measurements on a NaCl crystal immersed in liquid (ethanol) surroundings displayed an increase of the effective contact stiffness, K eff ,...

In situ changes in the nanofriction and microstructures of ionic liquids (ILs) on uncharged and charged surfaces have been investigated using colloid probe atomic force microscopy (AFM) and molecular dynamic (MD) simulations. Two representative ILs, [BMIM][BF 4 ] (BB) and [BMIM][PF 6 ] (BP), containing a common cation, were selected for this study....

We have investigated the influence of the geometric shape bounding the scan pattern on the orientation of the nanoripples evolved from a polystyrene surface scraped by a silicon tip. Atomic force microscopy measurements at ambient conditions are compared with numeric simulations based on a continuum model describing the time evolution of a generic...

We report the formation of spherical particles (up to 250 nm in diameter) from polystyrene surfaces repeatedly scratched by atomic force microscopy nanotips (nominal radius < 10 nm) along a series of parallel lines. The particles nucleate from the crests of the ripple profiles formed in the beginning of the scratch process. They are subsequently de...

We present a comparative study of nanoexfoliation on bulk, layered materials (MoS2, WSe2, HOPG, and mica) conducted via atomic force microscopy (AFM). The samples were scratched by single crystal diamond probes with varying scan velocities and normal forces. Friction forces measured during the scratch tests and post-mortem topography images allow a...

Since the device performance and stability of polymer solar cells strongly depend on the interfacial charge extraction layers, the hole transport layer (HTL) properties are crucial. Furthermore, unfavorable interactions with the electrode or the photoactive layer should be screened and prevented. We investigated organic solar cells of conventional...

Friction-induced energy dissipation impedes the performance of nanomechanical devices. Nevertheless, the application of graphene is known to modulate frictional dissipation by inducing local strain. This work reports on the nanomechanics of graphene conformed on different textured silicon surfaces that mimic the cogs of a nanoscale gear. The variat...

We present the results of friction experiments performed by manipulation of oxidized platinum nanoislands on highly oriented pyrolytic graphite (HOPG) substrates through atomic force microscopy (AFM). The oxidation of the platinum nanoislands, performed via mild plasma exposure, is confirmed through X-ray photoelectron spectroscopy (XPS) and high-r...

Non-hydrogenated diamond-like carbon (DLC) films doped with metals and oxygen were deposited by direct current magnetron sputtering. The influence of chromium and nickel on the surface morphology, elemental composition, bonding structure, adhesion force, optical transmittance and nanohardness of the films was characterized by atomic force microscop...

Two-dimensional materials, in particular graphene, exhibit a low friction coefficient and good wear properties. However, the tribological properties of these materials strongly depend on faint differences at the atomic level, and the coexistence of different type of atomic defects in studied samples up to date led to experimental results difficult...

Friction-induced energy dissipation impedes the performance of nanoscale devices during their relative motion. Nevertheless, an ingeniously designed structure which utilizes graphene topping can tune the friction force signal by inducing local strain. The present work reports capping of graphene over Si grooved surfaces of different pitch lengths f...

The emergence of surface patterns on the surfaces of compliant materials subject to plowing wear is a complex problem which can be quantitatively characterized, e.g., on polymer surfaces scraped by an atomic force microscope (AFM) tip. Here we explore the applicability of a phenomenological model recently introduced to describe this phenomenon. Bas...

Controlling friction on the nanometer scale is one of nowadays’ challenges for scientists and engineers. Since the first observation of atomic friction reported by Mate et al. for a tungsten tip sliding on graphite, a lot of progress has been made in the understanding of this phenomenon on the atomic scale. An accurate description of the motion of...

Cleaved dolomite (CaMg(CO3)2) crystals were immersed in supersaturated, saturated, and undersaturated solutions with respect to zabuyelite (Li2CO3), and the growth process was characterized using atomic force mi-croscopy (AFM) and scanning electron microscopy (SEM). In all cases, overgrowths formed by 2D-nucleation could be clearly distinguished in...

The surface structures resulting from scratching monolayer MoS2 on SiO2 and multilayer MoS2 using diamond nanotips with normal forces up to 3μN and scan velocities up to 10μm/s in ambient conditions are compared. In both cases the damage process initiates with normal forces of about 2μN. As shown by postmortem AFM images the monolayer is peeled off...

Single crystal gold clusters (10 nm in size) have been collectively manipulated on mono- and bi-layered MoS 2 islands (up to 20 µm) grown on SiO 2 using AFM. On the monolayer the clusters tend to move in a direction corresponding to the zigzag alignment of the Mo and S atoms, and assemble into long striation patterns parallel to the scan direction....

Understanding the time evolution of contact strength in silica nanocontacts is of great fundamental and practical relevance in diverse areas like earthquake dynamics, wafer bonding mechanisms, as well as MEMS applications. The logarithmic increase of contact strength with hold time, termed contact aging, can be “quantitative” due to deformation cre...

The structures produced by a sharp tip scraping a compliant surface are modeled in the illustrative case of scan patterns formed by a series of parallel lines. This is made possible by a modified version of the Prandtl model for stick-slip friction, with an interaction energy landscape replicating the morphology of the evolving surface. As a result...

Cryo-electron microscopy can determine the structure of biological matter in vitrified liquids. However, structure alone is insufficient to understand the function of native and engineered biomolecules. So far, their mechanical properties have mainly been probed at room temperature using tens of pico-newton forces with a resolution limited by therm...

We have investigated the time evolution of sliding friction between colloidal spheres of PMMA (with diameters of 3 μm and 9.6 μm) supported by an AFM cantilever and a SiO2 grating consisting of alternated slopes of ± 55° and flat areas, and periodicity comparable or below the sphere diameters. With the larger sphere we recognize a reproducible ‘rev...

The cover image shows topographically confined fibrinogen molecules on a nanostructured polymeric surface. The in situ observation of single molecule dynamics revealed that fibrinogen diffuses perpendicularly to its major axis via a Sansetsukon-like nanocrawling mechanism. The diffusion mechanism is supported by the intrinsic flexibility of fibrino...

Strukturkeramiken bestehend aus einer keramischen Matrix mit einer Zweitphase aus metallischen Werkstoffen stellen ein attraktives Kompositmaterial mit hoher Verschleißfestigkeit und exzellenten Hochtemperatureigenschaften dar. Das in der vorliegenden Arbeit verwendete Komposit besteht aus einer keramischen Al2O3 Matrix. Durch die duktile metallisc...

We report on the formation of regular surface ripples accompanying microscratching of vitreous silica using Berkovich diamond tips. The tips were pulled laterally along the surface with varying normal load of up to 30 mN and scan velocity of up to 500μm/s. Post mortem AFM analysis and independent confirmation through laser scanning microscopy revea...

Surface nanostructures are increasingly more employed for controlled protein assembly on functional nanodevices, in nanobiotechnology and nanobiomaterials. However, the mechanism and dynamics of how nanostructures induce order in the adsorbed protein assemblies are still enigmatic. Here we use single-molecule mapping by accumulated probe trajectori...

We have performed AFM nanomanipulation experiments on triangular Au islands (with typical linear size of 25–80 nm) previously grown on a MoS2 surface. These islands are found to move along preferential directions, independently of the angle of attack of the scanning probe. A comparison between molecular-dynamics simulations and atomically resolved...

Due to their outstanding anisotropic mechanical properties along the fiber axis, carbon fibers are used to reinforce polymers (CFRP) or concrete (ECC). In this context, the interface between the fiber and the surrounding matrix material plays a key role for the reinforcement mechanism. Different methods including plasma oxidation, chemical or elect...

Advanced structural composites consisting of a ceramic Al2O3 matrix, a ductile metallic Niobium phase and dispersed ZrO2 nanoparticles are characterized by high wear resistance, excellent high-temperature properties, and high fracture toughness and are therefore attractive for numerous technical applications. In this context, a key point is related...

Growth of otavite (CdCO3) and spherocobaltite (CoCO3) has been promoted on dolomite (10.4) surfaces at room temperature by immersing cleaved dolomite crystals in highly supersaturated solutions with respect to those phases. In situ Atomic Force Microscopy (AFM) observations show that otavite and spherocobaltite overgrow preferentially on dolomite s...

Similar to normal indentation studies, structural compaction and shear flow occur also in the lateral deformation of glass surfaces through scratching. Here, we apply instrumented indentation with tangential displacement in order to study the elastic-plastic regime of scratch-deformation on silica, borosilicate and soda lime silicate glasses. We ad...

Friction force microscopy (FFM) in aqueous environments has recently proven to be a very effective method for lattice-resolution imaging of crystal surfaces. Here we demonstrate the use of ethanol for similar measurements on water-soluble materials. Lattice resolved frictional stick-slip traces of a cleaved NaCl(100) surface submerged in ethanol ar...

The formation and properties of laser-induced periodic surface structures (LIPSS) were investigated on carbon fibers under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. The LIPSS were fabricated in an air environment at normal incidence with different values of the laser peak fluence...

We report high-resolution surface morphology and friction force maps of polycrystalline organic thin films derived by deposition of the n-type perylene diimide semiconductor PDI8-CN2. We show that the in-plane molecular arrangement into ordered, cofacial slip-stacked rows results in a largely anisotropic surface structure, with a characteristic saw...

Laser-induced periodic surface structures (LIPSS) were selectively fabricated on the metal phase of Al2O3-nZrO2-Nb (78.3–1.7–20 vol.%) ceramic matrix composites. For this purpose, sample surfaces were irradiated with fs-laser pulses (τ = 300 fs, λ = 1025 nm) of different laser peak fluences ranging from 0.23 to 0.40 J/cm2. The structured surfaces w...

We have performed molecular dynamics simulations of nanomanipulation experiments on short single-stranded DNA chains elastically driven on a graphene surface. After a brief transient, reproducible stick-slip cycles are observed on chains made by ten units of thymine, cytosine, adhenine and guanine. The cycles have the periodicity of the graphene su...

In this work we present friction-force microscopy (FFM) lattice-resolved images acquired on the (100) facet of the semiconductor organic oligomer (2Z,2′Z)−3,3′-(1,4-phenylene)bis(2-(4-butoxyphenyl)acrylonitrile) (β-DBDCS) crystal in water at room temperature. Stick-slip contrast, lateral contact stiffness, and friction forces are found to depend st...

Single molecule force spectroscopy of DNA strands adsorbed at surfaces is a powerful technique used in air or liquid environments to quantify their mechanical properties. Although the force responses are limited to unfolding events so far, single base detection might be possible in more drastic cleanliness conditions such as ultra high vacuum. Here...

We demonstrate how an exponentially saturating increase of the contact area between a nanoasperity and a crystal surface, occurring on time scales governed by the Arrhenius equation, is consistent with measurements of the static friction and lateral contact stiffness on a model alkali-halide surface at different temperatures in ultrahigh vacuum. Th...

Friction has long been the subject of research: the empirical da Vinci-Amontons friction laws have been common knowledge for centuries. Macroscopic experiments performed by the school of Bowden and Tabor (Bowden and Tabor 1950) revealed that macroscopic friction can be related to the collective action of small asperities. Over the last 25 years, ex...

Progress in the general understanding of structure-property relationships in organic devices requires experimental tools capable of imaging structural details, as molecular packing or domain attributes, featuring ultra-thin films. An operation mode of scanning force microscopy, related to friction force microscopy (FFM) and known as transverse shea...

Organic semiconductors (OSC) are attracting much interest for (opto)electronic applications, such as photovoltaics, LEDs, sensors or solid state lasers. In particular, crystals formed by small π-conjugated molecules have shown to be suitable for constructing OSC devices. However, the (opto)electronic properties are complex since they depend strongl...

The sliding of a sharp nanotip on graphene completely immersed in water is investigated by molecular dynamics (MD) and atomic force microscopy. MD simulations predict that the atomic-scale stick-slip is almost identical to the one found in ultra-high vacuum. Furthermore, they show that water plays a purely stochastic role on sliding (solid-to-solid...

A golden opportunity for graphene Reducing friction can limit wear and improve the energy efficiency of mechanical devices. Graphene is a promising lubricant because the friction between sheets is minuscule under certain circumstances. Kawai et al. show that the same ultra-low frictional properties extend to other surfaces. They find ultralow frict...

We have studied the influence of anisotropic nanopatterns (ripples) on the adhesion and morphology of mouse neural stem cells (C17.2) on glass substrates using cell viability assay, optical microscopy and atomic force microscopy. The ripples were produced by defocused ion beam sputtering with inert Ar ions, which physically remove atoms from the su...

Inelastic Helium Atom Scattering (HAS) is suitable to determine low-energy (few meV) vibrations spatially localized on structures in the nanometer range. This is illustrated for the nanodomes that appear often on graphene (Gr) epitaxially grown on single crystal metal surfaces. The nature of the inelastic losses observed in Gr/Ru(0001) and Gr/Cu/Ru...

The low temperature mechanical response of a single porphyrin molecule attached to the apex of an atomic force microscope (AFM) tip during vertical and lateral manipulations is studied. We find that approach-retraction cycles as well as surface scanning with the terminated tip result in atomic-scale friction patterns induced by the internal re-orie...

Lateral Force Microscopy (LFM) is a very suitable technique to investigate the structure and reactivity of mineral surfaces in liquids. Studies performed in the last two decades have shown that the dissolution and growth of mineral surfaces immersed in water and aqueous solutions can be monitored by recording friction signals with LFM. Moreover, th...

This chapter reviews friction force microscopy experiments that reveal atomic-scale processes in single asperity contacts during sliding. Different regimes of atomic friction will be discussed including smooth sliding with low dissipation and the dissipative atomic stick–slip motion, where the tip jumps from one lattice site to the next. Furthermor...

Wear on the nanoscale, as evidenced by the formation of periodic ripples on a model polystyrene thin film, is shown to be suppressed by the application of ultrasonic vibrations of amplitude Aexc, while a sharp tip is sliding on it with a normal force in the μN range. The corrugation of the typical ripple pattern which is formed in the absence of vi...

Combining the classical theories of contact mechanics and lubrication with the study of friction on the nanometer range, this multi-scale book for researchers and students alike guides the reader deftly through the mechanisms governing friction processes, based on state-of-the-art models and experimental results. The first book in the field to inco...

When the shear stress on a compliant surface exceeds the yield strength of the material, a periodic wrinkle pattern is often observed. This phenomenon has been also recognized at the nanometer scale on polymers, metals, ionic crystals and semiconductors. In those cases, the mechanical stress can be efficiently provided by a sharp indenter elastical...

Gold nanospheres have been manipulated by atomic force microscopy on a rippled glass surface produced by ion beam sputtering and coated with an ultrathin (10 nm thick) graphitic layer. This substrate is characterized by irregular wavy grooves running parallel to a preferential direction. Measurements in ambient conditions show that the motion of th...

The transition from atomic stick-slip to continuous sliding has been observed in a number of ways. If extended contacts are moved in different directions, so-called structural lubricity is observed when the two surface lattices are non-matching. Alternatively, a “superlubric” state of motion can be achieved if the normal force is reduced below a ce...

The reliability of ultrathin organic layers as active components for molecular electronic devices depends ultimately on an accurate characterization of the layer morphology and ability to withstand mechanical stresses on the nanoscale. To this end, since the molecular layers need to be electrically decoupled using thick insulating substrates, the u...

Significance Mechanical properties of biopolymers such as DNA and proteins have been studied to understand the details of complex processes in living systems via systematic statistical analyses of repeated measurements. However, the mechanical behavior of a single molecular chain pulled off a surface has never been investigated with atomic-scale re...

The influence of out-of-plane and in-plane contact vibrations and temperature on the friction force acting on a sharp tip elastically pulled on a crystal surface is studied using a generalized Prandtl- Tomlinson model. The average friction force is significantly lowered in a frequency range determined by the "washboard" frequency of the stick-slip...

The influence of lateral vibrations on the stick-slip motion of a nanotip elastically pulled on a flat crystal surface is studied by atomic force microscopy (AFM) measurements on a NaCl(001) surface in ultra-high vacuum. The slippage of the nanotip across the crystal lattice is anticipated at increasing driving amplitude, similarly to what is obser...