Nanosystem Implementation Using Nanochannels of Nanoporous Membranes

We are currently developing a novel fabrication technique for the implementation of nanosystems utilizing the nanochannels in nanoporous membranes. The technique is CMOS-compatible and has the potential for volume commercial manufacturing. The technique is based on the anodization, or electrolytic oxidation, of a thin film of aluminum to form a nanoporous alumina membrane, which is used as a guide to implement the nanosystems. The underlying principle of the fabrication technique is that when aluminum is anodized in a suitable acidic electrolyte under controlled conditions, it oxidizes to form a hydrated aluminum oxide (alumina) containing a two dimensional hexagonal array of cylindrical pores. The pore diameter and the inter-pore spacing depend on the anodization conditions and the substrate parameters, and can be varied between 4 nm to 100s of nm; the pores can be several microns deep. Due to the excellent periodicity of the pores, and the ability to control the pore diameters, such anodized alumina films can be used as templates for the fabrication of periodic arrays of nanostructures. In fact, the pores in alumina templates have been used to synthesize a variety of metal and semiconductor nanostructures. In addition, the template can also be used as a mask for pattern transfer to create periodic arrays of pores on a substrate. While most of the work in this field has focused on bulk aluminum, the use of a bulk aluminum substrate precludes most photonic and electronic applications. To overcome this, we have developed a thin film alumina template technology that allows the fabrication of nanoporous membranes consisting of nanochannels with diameters ranging between 4 nm to 10s of nm. By using a novel process, we convert the nanoporous templates into an array of nanochannels supported by the membrane. These nanochannels are then used as guides to deposit nanoparticles (nanodots, nanotubes and nanopillars) to form the desired nanosystem. The nanoparticles are primarily deposited by electrophoretic techniques. We are currently using this technique to implement nanosystems based on CdSe quantum dots and carbon nanotubes with applications in broad ranging fields including multispectral detectors, photonics, gas sensors and high efficiency solar cells. In this paper, we provide a description of the fabrication technique as well as some of the nanosystems currently under development.