Layer-by-Layer Assembly of Rectifying Junctions in and on Metal Nanowires

Abstract

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

Langmuir monolayers of gold nanoparticles: from ohmic to rectifying charge transfer

“…Within the potential range of −0.6 to +0.5 V the current is essentially zero beyond which the current starts to increase rapidly, a behavior akin to Coulomb blockade. Rectifying charge transfer has also been observed previously with nanowires involving metal-semiconductor heterojunctions [17], as well as nanoparticle organized ensembles sandwiched between dissimilar cathodes and anodes [6]. In these earlier cases [6,17], the rectifying features were accounted for by the charge injection at one of the interfaces.…”

“…Rectifying charge transfer has also been observed previously with nanowires involving metal-semiconductor heterojunctions [17], as well as nanoparticle organized ensembles sandwiched between dissimilar cathodes and anodes [6]. In these earlier cases [6,17], the rectifying features were accounted for by the charge injection at one of the interfaces. In the present system involving symmetrical experimental setup of the IDA fingers and the nanoparticle monolayers, the observations of asymmetrical voltammetric behaviors are rather surprising.…”

“…4), which seems to imply a memory effect of the nanoparticle thin films. Again, these unique charge-transfer behaviors can be attributable to the interfacial dipole properties of the nanoparticle molecules where the alignment of the nanoparticle dipoles generated during electron transfer process might not be readily switched by the bias polarity [17,18]. From the above studies (Figs.…”

Challenges and breakthroughs in recent research on self-assembly

“…Recently, research of this method has become application-oriented as can be seen in several reports including surface modification for superhydrophobicity [868,869], sensor preparation [870][871][872][873][874], electrochromic devices [875], photochromic devices [876], thin film transistors [877], fuel cells [878], solid-state photovoltaic devices [879], rectifying junctions [880], and chiral switching [881].…”

Template synthesis of nanomaterials

“…The variety of materials includes but is not limited to: magnetic nanowires and superlattices for anisotropic magnetoresistance, AMR, giant magnetoresistance, GMR, and tunnelling magnetoresistance, TMR, memory applications [7,11,32,, polymer nanowires and nanotubes [68,69], semiconductor nanowires [70], rectifiers [37,71,72], single-crystal nanowires [36,[73][74][75][76][77][78][79][80][81][82][83][84][85], superconducting nanowires [86][87][88][89][90], and transistors [91]. Also, there is continued use of track-etched mica [92][93][94].…”