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Current-voltage experiments on a highly ordered array of carbon nanotubes interfaced with silicon reveal interesting features arising from the regular array of heterojunctions between one-dimensional (1D) and three-dimensional materials. At high temperature, the vertically aligned and ordered nanotubes behave as an array of point junction contacts to the silicon below, which merge into a planar junction as temperature decreases. This model is further supported by the observation of signature space charge limited conduction, whose origin is attributed to deep levels in the silicon substrate and to the strong field enhancement due to the quasi-1D nanotubes.

The properties of nanosize heterojunctions are of increasing interest as the trend of scaling down the size of electronic devices continues. We present here the direct growth of carbon nanotubes on a silicon substrate to form a heterodimensional heterojunction. Current-voltage measurements reveal the characteristics of a Schottky diode. However, a close examination of the data suggests that the device is limited in the forward bias direction by space charge limited current. In the reverse direction, it is functionally altered by the heterodimensionality of the junction and its associated enhancement of field emission.

Hafnium nitride films were prepared on the Si(100) substrates by the metal-organic chemical vapor deposition method using Hf[N(C2H5)2]4. The prepared samples were then oxidized in air, followed by rapid-thermal annealing to produce HfOxNy thin films, meanwhile the associated physical properties were investigated. The x-ray photoelectron spectroscope analysis unveiled that the composition of the films is HfOxNy. In addition, the films after the rapid-thermal annealing treatments at various temperatures revealed salient features in their physical properties, such as capacitance and conductivity. On this basis, the feasibility of using the HfOxNy layers as high-k dielectrics in complementary metal oxide semiconductor transistors was also discussed.

The authors describe the properties of electronically active nanowires that can be assembled via DNA directed growth on a nanostructured array. DNA-modified nanoparticles are used to site-specifically address the tips of vertically aligned carbon nanotubes (CNTs) that serve as catalysts for the growth of zinc oxide (ZnO) nanorods. Using conductive probe atomic force microscopy, they measured the conductance characteristics of single ZnO-CNT structures under various force and illumination conditions and at different sites in a large array, thereby establishing that DNA directed formation of multimaterial, optically active nanostructures can yield devices that are electronically functional at the nanometer scale. The inherent ability of DNA to carry and convey encoded information provides the basis for targeted synthesis of nanostructured devices.