AVS 45th International Symposium
    Nanometer-scale Science and Technology Division Tuesday Sessions
       Session NS-TuA

Paper NS-TuA6
Fabrication of Metallic Nanowires via UHV-STM Lithography and Thermal CVD

Tuesday, November 3, 1998, 3:40 pm, Room 321/322/323

Session: Quantum Wires and Quantum Dots
Presenter: M.C. Hersam, University of Illinois, Urbana-Champaign
Authors: M.C. Hersam, University of Illinois, Urbana-Champaign
G.C. Abeln, University of Illinois, Urbana-Champaign
D.S. Thompson, University of Illinois, Urbana-Champaign
J.S. Moore, University of Illinois, Urbana-Champaign
H. Choi, University of Illinois, Urbana-Champaign
S.-T. Hwang, University of Illinois, Urbana-Champaign
J.W. Lyding, University of Illinois, Urbana-Champaign
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The selective removal of hydrogen from a passivated Si(100) surface with an ultrahigh vacuum (UHV) scanning tunneling microscope (STM) allows nanometer-sized "templates" of clean Si(100) to be defined on an otherwise unreactive surface. By delivering chemically reactive species to the surface in the gas phase, different materials can be selectively deposited on the unpassivated Si(100) areas. In particular, nanopatterned metallization is achieved through selective thermal chemical vapor deposition (CVD) of organometallic precursor molecules. This paper systematically analyzes such precursor molecules to determine their suitability for selective CVD of metal on Si(100) in UHV. Initially, a novel aminoalane precursor was employed for CVD of aluminum at ~200°C. STM images of the surface after exposure to this precursor suggest monolayer coverage and evidence of a 2X2 reconstruction. However, variation of the dose and deposition conditions did not lead to the growth of a thicker film. Hence, in an effort to produce a more receptive surface for the growth of metallic thin films, CVD of nucleating agents (e.g., TiCl@sub 4@) was also studied. XPS and STM data show the selective deposition of Ti on clean versus H-passivated Si(100) after TiCl@sub 4@ exposure at room temperature. In an effort to grow TiN, the TiCl@sub 4@ experiments were repeated on an ammonia coated Si(100) surface. Again, XPS and STM data show the selective deposition of Ti. Finally, multiple precursor molecules were integrated for the growth of multi-layer structures. As a footnote, our efforts for interfacing these STM patterned nanowires with macroscopic external electronics will be updated.