Fabrication of Nanoperiodic Surface Structures by Controlled Etching of Dislocations in Bicrystals

  Rikard A. Wind, Martin J. Murtagh, Fang Mei, Yu Wang,
  Melissa A. Hines, and Stephen L. Sass

  Departments of Chemistry and Materials Science and Engineering

  Cornell University, Ithaca, NY 14853

Today, the smallest feature on the best microprocessor in commercial production is 150 nm. In contrast, the distance between binding sites on a human antibody is 10 nm -- our smallest devices are 15 times larger than Nature's! Although impressive strides are being made in the microelectronics industry, nanofabrication at the 10 nm length scale will remain beyond the grasp of conventional nanofabrication for the foreseeable future. For the last 35 years, the performance of microelectronic devices has increased exponentially with time. This is known as "Moore's Law." The performance of lithographic tools has also increased exponentially. If this trend continues -- a very questionable assumption after the year 2010 -- the microelectronics industry will not reach biomolecular length scales until the year 2025.

Of course, matter can be manipulated at the atomic length scale using a scanning tunneling microscope, and a number of structures have been generated in this fashion. Unfortunately, serial technologies, such as those that require direct writing, are very slow and thus very costly. The commercialization of nanometer-scale devices will presumably require a parallel process capable of producing millions of devices at a time.

We have developed a new technique for the controlled fabrication of nanometer-scale periodic surface structures. In principle, this technique can be used to prepare features with a continuously variable spacing between 2-100 nm. (For comparison, the spacing between atoms in a silicon crystal is about 0.24 nm.) As proof of concept, we have fabricated of an array of single-crystal silicon nanostructures with a 38 nm spacing. Each nanostructure is about 25 nm in diameter -- 100 atoms wide! To achieve structures at this very fine length scale, we make use of the inherent spacing and periodicity of atoms in a silicon lattice.