Precision tailoring of the dimensions and chemistry of materials at the nanometer scale is only one prerequisite to the realization of the potential of nanotechnology. For many applications, even greater challenges are associated with positioning of nanomaterials in the desired location within the device, and their interfacing with the functional electronic and/or optical circuitry, all at affordable cost and high throughput. This is especially true when the device concept requires that all nanoscale elements are behaving coherently, and that the response of the array retains the characteristics of individual elements.
In this presentation we will overview our progress in addressing these challenges. The heart of the approach is based on templated nanofabrication and micromachining with one of the most fascinating self-organized nanoporous materials, anodic aluminum oxide (AAO). Uniform and parallel nanometer-scale pores of AAO could be used to host arrays of nanodots, nanowires or nanotubules. The pore diameter is tunable from 5 nm to several hundred nanometers, with the pore density in the range from 109 to 1011 cm-2. On the low end, the pore diameter approaches the carrier mean free path for selected metal and semiconductors, suggesting that quantum confinement effects might be realized. Pore diameter could be modulated along their length, opening additional opportunities for nanoelectronics. Nanotemplates could be prepared on Al, silicon and other substrates, as well as in a free-standing form. Various deposition techniques, such as electrodeposition, polymerization, sol-gel, and CVD could be used to prepare arrays of nanostructures. The templated approach was pioneered independently by several groups, and is successfully used today by an increasing number of researchers.
Resulting arrays of nanostructures encapsulated in AAO matrix could then be manipulated in many ways to integrate them into devices. The surface of AAO nanotemplates could be patterned prior to deposition to obtain domains of nanowires only in required areas. Furthermore, due to its intrinsic anisotropy, anodic alumina could be micromachined with great flexibility. This is a hybrid MEMS-type process, which combines design and processing features of both surface and bulk micromachining, and could be used to form 2- and 3-D microstructures and microdevices with integrated nanoarrays. We will present case studies for several types of such devices, including polarization-sensitive materials for radiation detectors, energy conversion materials, field emission cathodes and gas microsensors. A number of prototypes of these devices were produced, demonstrating performance enhancements in comparison with conventional devices.
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