研究目的
Understanding the adhesive and frictional properties of nanosystems, such as molecules, 3D nanoclusters or 2D adsorbates, polymeric chains, etc., on structurally well-characterized crystalline substrates is of key importance for both fundamental sciences, as e.g. contact mechanics and nanotribology, and technological applications.
研究成果
We have described extensive non-equilibrium molecular dynamics (NEMD) simulations of detachment dynamics by vertical lifting of a graphene nanoribbon adsorbed on Au(111), along with experimental data of the tip-applied force derivative. Results show that the steady state of this vertical dynamics is characterized by the detachments of the individual physisorbed units of the GNR, with the GNR unit cell 0.42 nm periodicity, in both the experimental tip frequency shift and the simulated vertical-force pro?les.
研究不足
The level of quantitative agreement between theory and experiment is limited by the use of simple two-body Lennard-Jones potentials to describe simultaneously adhesive interactions and the interface corrugation.
1:Experimental Design and Method Selection:
AFM nanomanipulations and molecular-dynamics (MD) simulations were used to study the detachment dynamics of graphene nanoribbons (GNRs) on Au(111).
2:1). Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Seven carbon atoms wide (n = 7) armchair GNRs are synthetized on a clean Au(111) surface at
3:8 K in UHV. List of Experimental Equipment and Materials:
A commercially available Omicron low-temperature scanning tunneling microscopy (STM)/atomic force microscopy (AFM) system, operating in ultra-high vacuum at
4:8 K. Experimental Procedures and Operational Workflow:
The tip is positioned at one GNR end, with a low bias voltage (~ 2 mV). When the junction between the tip and the GNR is established, an abrupt change in the tunneling current is detected. Subsequently, a dynamical AFM mode is turned on, with a vertical oscillation amplitude ~ 43 pm. The tip is then slowly retracted while recording the frequency shift as well as the energy dissipation.
5:Data Analysis Methods:
The frequency shift is proportional to the derivative of the vertical force that the tip exerts on the GNR: dFext/dz.
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