Feb 10, 2009
Alumina nanosieves sort electrons
Nanoporous materials are being employed in a range of applications including nanolithography and pattering. Because samples can be fabricated with pore diameters below 50 nm in arrays extending over many centimeters squared, the materials provide a means of producing large-scale patterns that cannot be achieved using conventional electron-beam lithography techniques.
Simply being nanoporous, however, is not enough if you want to use these materials for transmission applications. The nanotubes also need to be hollow and free of internal obstructions.
In a recent issue of Nantotechnology, researchers at the University of Melbourne, Australia, described novel ways of fabricating and characterizing such electron transparent, nanotubular arrays in alumina. The group demonstrated that the nanotube arrays are extremely well aligned to each other, which allows the membrane to act as an electron collimator or a physical sieve. Even small angular offsets (<1°) of the membrane were sufficient to block electron transmission, which is indicative of the extremely high aspect ratios that can be achieved (>300:1).
Looking ahead, the authors hope to create two-dimensional arrays of coupled nitrogen vacancy centre quantum dots in diamond by placing the nanotubular arrays in the path of low-energy ion beams. Other applications may include the templated growth of nanotube and nanowire arrays.
About the author
The work was performed at the University of Melbourne (Australia) in the School of Physics and the Bio21 Molecular Science and Biotechnology Institute. The work was financially supported by the Australian Research Council (ARC). Jing-Hua Fang is a PhD student studying materials science at the University of Melbourne. She was financially supported through the provision of an International Postgraduate Scholarship. Dr Paul Spizzirri is a postdoctoral researcher in the Centre for Quantum Computer Technology. Dr Sergey Rubanov is an electron microscopist at Bio21. Dr Alberto Cimmino is also a postdoctoral researcher in the Centre for Quantum Computer Technology and Prof. Steven Prawer is the Inaugural Director of the Melbourne Institute of Materials (MIM) at the University of Melbourne.