1.5    Mechanics of a-Spot Formation

1.5.1    Smooth Interfaces

In an electrical interface, metal-to-metal a-spots are subjected to a variety of mechanical forces that influence the shape and dimensions of spots with time, even in apparently stationary junctions. It is well known that clean smooth surfaces pressed into intimate contact may adhere strongly under the action of intermolecular forces [15,142]. Figure 1.37b illustrated the dependence of contact resistance on mechanical load obtained with smooth oxide-free aluminum surfaces generated in ultra-high vacuum [80]. As the load was increased, the resistance dropped rapidly to a low value and remained relatively constant during the unload phase. As is evident in the figure, the oxide-free ...

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