  Since the first measurement of electron tunneling through an organic
monolayer in 1971,(Mann and Kuhn, 1971) and the gedanken experiment of a
molecular current rectifying diode in 1974,(Aviram and Ratner, 1974)
molecular-scale electronics have attracted a growing interest, both for basic
science at the nanoscale and for possible applications in nano-electronics. In
the first case, molecules are quantum object by nature and their properties can
be tailored by chemistry opening avenues for new experiments. In the second
case, molecule-based devices are envisioned to complement silicon devices by
providing new functions or already existing functions at a simpler process
level and at a lower cost by virtue of their self-organization capabilities,
moreover, they are not bound to von Neuman architecture and this may open the
way to other architectural paradigms. After a brief overview of the
nanofabrication of molecular devices, we review in this chapter, the electronic
properties of several basic devices, from simple molecules such as molecular
tunnel junctions and molecular wires, to more complex ones such as molecular
rectifying diodes, molecular switches and memories.
