Rapid prototyping of bottom-up nanostructure circuits is demonstrated, utilizing metal deposition and patterning methodology based on combined focused ion and electron beam induced decomposition of a metal−organic precursor gas. Ohmic contacts were fabricated using electron beam deposition, followed by the faster process of ion beam deposition for interconnect formation. Two applications of this method are demonstrated: three-terminal transport measurements of Y-junction carbon nanotubes and fabrication of nanocircuits for determination of electromechanical degradation of silver nanowires.

Room-temperature ferromagnetism is observed in chemically synthesized powder samples of Sn1−xCoxO2 with x=0.005 and 0.01. Magnetic hysteresis loops are observed at 300K with coercivity Hc∼630Oe, saturation magnetization Ms∼0.133μB∕Co ion, and about 31% remanence. Analyses of the magnetization data of paramagnetic samples with x=0.01 and 0.03, measured as a function of temperature (3–330K) and magnetic field (up to 65kOe), indicate the presence of Co+2 ions with spin S=3∕2. Magnetic data obtained from samples prepared at different temperatures indicate that the observed ferromagnetism for x⩽0.01 might have been triggered by changes in the oxygen stoichiometry.

The ability to interconnect different nanostructures is crucial to nanocircuit fabrication efforts. A simple and versatile direct-write nanolithography technique for the fabrication of interconnects is presented. Decomposition of a metalorganic precursor gas by a focused electron beam resulted in the deposition of conductive platinum nanowires. The combination of in situ secondary electron imaging with deposition allows for the simultaneous identification and interconnection of nanoscale components. However, the deposition was not entirely localized to the electron beam raster area, as shown by secondary ion mass spectrometry measurements. The electrical impact of the metallic spread was quantified by measuring the leakage current between closely spaced wires. The origins of the spread and strategies for minimizing it are discussed. These results indicate that, while this direct-write methodology is a convenient one for rapid prototyping of nanocircuits, caution must be used to avoid unwanted decoration of nanostructures by metallic species.

The electrical properties of the mismatched interface between InAs and GaP have been investigated. High-resolution transmission electron microscopy images show the presence of strain relieving, 90° misfit dislocations at this interface. Hall measurements and electrochemical capacitance–voltage profiling indicate the presence of a high-density sheet of carriers (electrons and holes) at the interface. A linkage is drawn between interfacial carriers and misfit dislocations. A model based on Fermi-level pinning in InAs at the interface by misfit dislocations is proposed to account for the observed electrical behavior.

We report the characteristics of molecular-beam epitaxy grown InAs on highly lattice mismatched (001) GaP substrates. Strain relaxation in this system occurs at low thickness by the generation of a periodic two-dimensional square grid network of 90° misfit dislocations at the heterointerface. The very high interface dislocation density (∼1013 intersections/cm2) exerts a unique influence on the electronic properties of the system. An extended defect structure at the intersection of 90° misfit dislocations is proposed to act as an ordered structural donor source. Hall effect measurements indicate that this source is fully ionized with a constant sheet carrier concentration of 1013 cm−2, irrespective of the InAs layer thickness, and exhibits no freeze out at low temperatures. We have also demonstrated that the electron mobility increases significantly with InAs layer thickness, reaching values in excess of 10 000 cm2/V s in nominally undoped layers. The high threading dislocation density (∼1010 cm−2) in the InAs epilayers does not appear to have a deleterious effect on the transport properties of majority carrier electrons.