Showing papers by "Adrian P. Sutton published in 1995"

Interfaces in Crystalline Materials

Abstract: The geometry of interfaces Dislocation for interfaces Models of interatomic forces at interfaces Models and experimental observations of structure Thermodynamics of interfaces Interface phases and phase transitions Segregation of solute atoms to interfaces Diffusion at interfaces Conservative motion of interfaces Non-conservative motion of interfaces: interfaces as sources/sinks for diffusional fluxes of atoms Electronic properties of interfaces Mechanical properties of interfaces.

Conditions for conductance quantization in realistic models of atomic-scale metallic contacts.

Abstract: We present a comparative analysis of tight-binding and free-electron calculations of the conductance of an atomic-scale metallic contact. The calculations are based on a full dynamic simulation of the atomic structure during the pulloff of the contact, for a range of temperatures. As in previous simulations, we find that the contact evolves through a series of mechanical instabilities and can become highly disordered prior to fracture. Both the mechanical evolution of the contact and the behavior of the conductance depend strongly on temperature. We find that conductance quantization is destroyed easily by irregularities in the shape of the contact and, in the tight-binding model, also in the internal atomic structure of the contact. In the tight-binding calculation conductance quantization is seen only at high temperature, when the contact geometry and structure become very regular. With the free-electron model, we see perfectly quantized conductance plateaus just prior to contact fracture, while the plateaus in the earlier history of the contact are washed out by tunneling. In the free-electron calculation, conductance quantization is seen both at low and at high temperature but is more prominent at high temperature. We use the tight-binding and free-electron results for the conductance to obtain a calibration curve relating the conductance to the constriction width. The calculated conductances lie significantly below the Sharvin limit but the inclusion of the first-order semiclassical correction to the Sharvin formula greatly improves the agreement.

Nanomechanics: — Atomic Resolution and Frictional Energy Dissipation in Atomic Force Microscopy

Abstract: A brief summary of mechanical behaviour of metals in nanometre scale contacts is given, drawing on both experimental data and molecular dynamics simulations. Adhesion leads to finite tip and surface contact at zero applied load, and inelastic deformation occurs at stresses far greater than bulk values. These effects lead to limits to the real space resolution of contact mode AFM. The generation of apparent atomic resolution, or Moire imaging is also described. Finally, the processes of energy dissipation in nanocontacts are discussed, both for hysteresis in normal loading cycles, and for frictional sliding.