Alumina membranes containing 200 nm diameter pores were replicated electroc
hemically with metals (Au and Ag) to make free-standing nanowires several m
icrons in length. Wet layer-by-layer assembly of nanoparticle (TiO2 or ZnO)
/polymer thin films was carried out in the membrane between electrodepositi
on steps to give nanowires that contained rectifying junctions. Concentric
structures with similar properties were prepared by first coating the membr
ane walls with multilayer films, and then growing nanowires inside the resu
lting tubules, or by growing films on the exposed surface of the nanowires
after dissolution of the membrane. The I-V characteristics of nanowires pre
pared by either technique show current rectifying behavior. The electronic
properties of Au(MEA)/(ZnO/PSS)(19)ZnO/Ag (MEA = mercaptoethylamine) device
s indicate that rectification is determined by charge injection at the meta
l/ZnO/PSS-film interface rather than by a tunneling mechanism. In the case
of Ag(TiO2/PSS)(9)TiO2/Au devices, switching behavior and hysteresis that c
ould not be described by Schottky or Fowler-Nordheim characteristics was fo
und. The combined replication/layer-by-layer synthetic approach allows one
to control both the geometry and the chemical composition of diode nanowire
devices.