Scanning Tunneling Microscopy-Based Fabrication of Nanometer Scale Structures

Abstract

We describe several STM-based techniques that we have developed for the fabrication of nanometer scale structures at room temperature. The techniques utilize processing with the biasing voltage/current of the tip of the microscope. Tunable laser radiation coupled to the gap induces multiphoton excitation or ionization processes of precursor gasses thus providing material selectivity to the process. We have made structures whose sizes range from a few hundred nanometers down to the size of individual atoms or molecules, on graphite, chemically passivated silicon, photoresist coated silicon, and organometallic-coated silicon surfaces. On the other hand, at small enough tunneling gaps, the chemical potential collapses allowing the tip to suck material off the surface, hence producing grooves. We have been able to fabricate continuous micrometer long lines of smallest widths ever (as small as 40 Å). We used this capability to fabricate all sorts of two-dimensional patterns: triangular, rectangular, circular, parallel lines, grids, and others in the shape of alphabets. In addition, we are in the process of integrating this capability with novel molecular beam epitaxy (MBE) methods to fabricate and analyze two and three dimensional nanometer scale structures such as quantum wires and dots, quantum gratings, arrays of quantum dots etc. We are presently using these techniques to construct and test the quantum interference transistor, a micrometer size metal oxide semiconductor field effect transistor (MOSFET) with a nanometer scale grating or grid embedded in its gate area. These advances have important implications to mass storage of information, which may lead to great reductions in the sizes of electronic circuits and devices.