Avalanche in adhesion

Smith, J. R.; Bozzolo, Guillermo; Banerjea, Amitava; Ferrante, John

doi:10.1103/physrevlett.63.1269

Cited by 144 publications

(87 citation statements)

References 13 publications

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“…2(a)-2(c)] the same dependence of the barrier on separation is found regardless of the method used ( A1 A2 A3 A ). Initially, during the approach, the barrier is approximately constant at 5.5 eV followed by a small monotonic increase until an abrupt jump into contact, in agreement with the theory of metal-metal point contacts [6,7]. However, the barrier determined when the 1,3-CHD molecule is approached [red curves in Figs.…”

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confidence: 59%

Measuring the Force of Interaction between a Metallic Probe and a Single Molecule

et al. 2006

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Precision current measurements are recorded at 5 K during the approach and contact between a Pt-inked probe and the carbon-carbon double-bond region of an isolated 1,3-cyclohexadiene molecule chemisorbed on a Si(100) surface. Scanning tunneling spectroscopic data reveal systematic features in the current at specific probe-molecule separations. Aided by density functional theory calculations, we show that these features arise from interaction forces between the probe and molecule, which can be interpreted as the relaxation of the probe-molecule system prior to and during contact. DOI: 10.1103/PhysRevLett.97.098304 PACS numbers: 82.37.Gk, 39.25.+k, 68.43.ÿh, 81.16.Ta There is enormous interest in the potential use of molecules in future electronic device technologies [1][2][3]. Although molecular electronics has the potential for the highest possible integration densities, the major difficulty in advancing this technology is establishing reliable contacts with molecules [1,4]. Not only is the influence of the contacting metal not well understood but the manner in which the contact perturbs the properties of molecules is a complete unknown [2,5], and precludes the rational design of molecular devices. In this Letter we introduce a novel STM-based method to measure the contact forces and interactions between a metallic probe and a single molecule. We show that, for a Pt-metal-''inked'' STM probe and a 1,3-cyclohexadiene (1,3-CHD) molecule on the Si(100) surface, there is a repulsive barrier at large separations followed by an attractive interaction associated with contact and chemical bond formation. This method is quite general and applicable to a wide range of molecular systems.To study the interaction between a single molecule and a STM probe it is necessary to develop a reliable method to control the chemical composition of the probe. This is accomplished by placing a single crystal metal sample [in this case Pt(111)] and the Si(100) substrate s[n -type As, <5 m cm] together in a sample holder that allows each to be heated and prepared. Each sample was then characterized by LEED, exposed at room temperature to less than 0.1% of a monolayer of 1,3-CHD, cooled to 80 K, transferred into a Createc LT-STM and cooled to 5 K for imaging [see Figs. 1(a) and 1(b)] and spectroscopic analysis [see Figs. 1(c)-1(e)]. Tungsten STM probes were cleaned by electron bombardment and then inked by drawing Pt atoms from the surface onto the end of the probe (see below). Figure 1(c) shows that the current increases exponentially during the approach to the Pt(111) surface, after which there is a sudden jump associated with contact formation [6 -8]. The exponential behavior of the current I follows the well-known distance dependence of the tunneling current [9-11]:where A is the apparent tunneling barrier height, Z is the probe-surface separation, and A 2 8m e 1=2 =h. The Pt surface is locally melted in the contact area and when the probe is withdrawn there is a clear hysteresis in the current due to the formation of a Pt metal nec...

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confidence: 59%

Measuring the Force of Interaction between a Metallic Probe and a Single Molecule

et al. 2006

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“…Atomistic simulations [2,13,14] have shown that when surfaces are brought into contact a jump occurs due to the adhesion forces between the metallic layers. However, this jump depends on the stiffness of the material and the geometry of the surfaces involved.…”

Section: Prl 98 206801 (2007) P H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

Formation of a Metallic Contact: Jump to Contact Revisited

et al. 2007

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The transition from tunneling to metallic contact between two surfaces does not always involve a jump, but can be smooth. We have observed that the configuration and material composition of the electrodes before contact largely determine the presence or absence of a jump. Moreover, when jumps are found preferential values of conductance have been identified. Through a combination of experiments, molecular dynamics, and first-principles transport calculations these conductance values are identified with atomic contacts of either monomers, dimers, or double-bond contacts.

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“…This ''adhesion avalanche'' phenomenon was previously predicted for Ni͑001͒ using the equivalent crystal method. 18 For the perfect alignment case, sliding is equivalent to shearing of a perfect crystal, leading to very high ''friction.'' Experiments conducted under similar conditions lead to cold welding.…”

Section: Deformation At Commensurate Interfacesmentioning

confidence: 99%

Friction anisotropy at Ni(100)/(100) interfaces: Molecular dynamics studies

Qi¹,

Cheng²,

Çağın

et al. 2002

Phys. Rev. B

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The friction of surfaces moving relative to each other must derive from the atomic interaction at interfaces. However, recent experiments bring into question the fundamental understanding of this phenomenon. The analytic theories predict that most perfect clean incommensurate interfaces would produce no static friction, whereas commensurate aligned surfaces would have very high friction. In contrast recent experiments show that the static friction coefficient between clean but 45°misoriented Ni͑001͒ surfaces is only a factor of 4 smaller than for the aligned surfaces ( ϳ0°) and clearly does not vanish ͑ is defined as the rotation angle between the relative crystallographic orientations of two parallel surfaces͒. To understand this friction anisotropy and the difference between analytic theory and experiment, we carried out a series of nonequilibrium molecular dynamics simulations at 300 K for sliding of Ni͑001͒/Ni͑001͒ interfaces under a constant shear force. Our molecular dynamics calculations on interfaces with the top layer roughed ͑and rms roughness of 0.8 Å͒ lead to the static frictional coefficients in good agreement with the corresponding experimental data. On the other hand, perfect smooth surfaces ͑rms roughness of 0 Å͒ lead to a factor of 34 -330 decreasing of static friction coefficients for misaligned surfaces, a result more consistent with the analytic theories. This shows that the major source of the discrepancy is that small amounts of roughness dramatically increase the friction on incommensurate surfaces, so that misaligned directions are comparable to aligned directions.

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Avalanche in adhesion

Cited by 144 publications

References 13 publications

Measuring the Force of Interaction between a Metallic Probe and a Single Molecule

Measuring the Force of Interaction between a Metallic Probe and a Single Molecule

Formation of a Metallic Contact: Jump to Contact Revisited

Friction anisotropy at Ni(100)/(100) interfaces: Molecular dynamics studies

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