AVS 47th International Symposium
    Processing at the Nanoscale/NANO 6 Monday Sessions
       Session NS+NANO6-MoA

Paper NS+NANO6-MoA3
Fundamental Approaches to Silicon-based Molecular Nanotechnology using the Scanning Tunneling Microscope

Monday, October 2, 2000, 2:40 pm, Room 302

Session: Manipulation of Atoms and Molecules
Presenter: M.C. Hersam, University of Illinois
Authors: M.C. Hersam, University of Illinois
N.P. Guisinger, University of Illinois
L. Liu, University of Illinois
J.W. Lyding, University of Illinois
Correspondent: Click to Email
The importance of molecular nanotechnology has recently been underscored by increased media, public, and government awareness of the subject. This paper outlines an approach for fabricating and characterizing single molecule units on the technologically significant Si(100) surface with the ultra-high vacuum scanning tunneling microscope (UHV-STM). Using feedback controlled lithography (FCL), individual H atoms can be removed from the Si(100)-2x1:H surface. The remaining dangling bond patterns serve as atomically precise templates upon which other materials can spontaneously self-assemble. By utilizing this selective chemistry in situ, several organic molecules (e.g., norbornadiene (NBE), copper phthalocyanine (CuPc), C@sub 60@, etc.) have been isolated. The mechanical, chemical, and electronic properties of these individual adsorbed species can then be immediately detected with the STM. For CuPc, the spatial extent of charge transfer from the substrate to the adsorbate is measured as a function of binding orientation. When the CuPc is reduced with ammonia, single molecule rotation is observed. STM spectroscopic measurements on C@sub 60@ reveal intra-molecular variations in the electronic density of states. A fundamental understanding of such phenomena will enable the design of nanoscale devices. For electronic applications, the application of lateral electrical fields to individual molecules is crucial. A fully compatible electrical contacting scheme based on p-n junctions will be presented. Efficient STM potentiometric location of these p-n junctions suggests their additional use as alignment markers. Finally, the robustness of this technique will be outlined. Even following exposure to ambient conditions, the in situ H-passivated Si(100) surface remains atomically pristine. The ability to combine nanolithography with wet chemical processing opens up new opportunities for nanoscale chemical and biological applications.