  The controlled fabrication of actively switchable atomic-scale devices, in
particular transistors, has remained elusive to date. Here we explain operation
of an atomic-scale three-terminal device by a novel switching mechanism of
bistable, self-stabilizing reconstruction of the electrode contacts at the
atomic level: While the device is manufactured by electrochemical deposition,
it operates entirely on the basis of mechanical effects of the solid-liquid
interface. We analyze mechanically and thermally stable metallic junctions with
a predefined quantized conductance of 1-5 G_0 in experiment and atomistic
simulation. Atomistic modeling of structural and conductance properties
elucidates bistable electrode reconstruction as the underlying mechanism of the
device. Independent room-temperature operation of two transistors at low
voltage demonstrates intriguing perspectives for quantum electronics and logics
on the atomic scale.
