Synthesis, characterization, and property measurement of novel metal-oxide-metal heterojunction nanowires with ferroelectric functionality

A new "bottom-up" paradigm of electronics offers the possibility of assembling virtually any electronic device using nanoscale building blocks to provide functionality. Essential to this vision is the synthesis of such building blocks with customized composition, morphology, and properties in a reproducible, controlled manner.;In the case of functional oxides, extensive studies have been carried out synthesizing all-oxide nanowires that are assembled across metal contact-pad electrodes to create devices. However, there are drawbacks to this approach including: high ohmic losses; the active oxide region is determined by spacing of the electrodes; the contacts made to the functional segment are on the side-wall of the nanowire; and making reproducible contacts over a range of devices is difficult.;In this context, metal-oxide-metal (MOM) heterojunction nanowires, where two Au nanowires are separated by a nanoscale segment of a functional oxide, offer several advantages over all-oxide nanowires. The MOM nanowire structure precisely defines the active oxide region within the building block itself and the metal interconnects are integrated within the building block making them more suitable for device assembly. In addition, the small interfacial area of the metal interconnects to the oxide offer the possibility of measuring coupled electronic properties of nanoscale volumes of oxides without substrate effects.;In this work, a novel method is developed to synthesize Au-TiO2 -Au, Au-BaTiO3-Au and Au-PbTiO3-Au MOM heterojunction nanowires. This is the first report of successful synthesis of MOM nanowires with ternary oxides. Results from the synthesis and characterization of these nanowires are presented.;In order to measure properties of these nanowires, single-nanowire-based devices are fabricated using the focused ion beam (FIB) direct write method to make connections to macroscale electrode pads. The charge transport properties are measured and show a non-linear, non-rectifying response. This response is shown to be due to a transition between ohmic and space-charge-limited-conduction (SCLC) and is investigated using Au-NiO-Au nanowires as a model system. In the Au-BaTiO3-Au and Au-PbTiO3-Au nanowire system, ferroelectric polarization measurements are performed using both electrical measurements and a scanning probe microscope approach.