AVS 49th International Symposium
    Nanometer Structures Friday Sessions
       Session NS-FrM

Paper NS-FrM5
Accurate Real-Space Measurements of Surface Lattice Parameters

Friday, November 8, 2002, 9:40 am, Room C-207

Session: Novel Surface Nanoprobes
Presenter: J.A. Kramar, National Institute of Standards and Technology
Authors: J.A. Kramar, National Institute of Standards and Technology
G.M. Witzgall, National Institute of Standards and Technology
V.P. Scheuerman, National Institute of Standards and Technology
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At the National Institute of Standards and Technology (NIST), we have built a metrology instrument called the Molecular Measuring Machine (M@super 3@) with the goal of performing nanometer-accuracy two-dimensional feature placement measurements over a 50 mm by 50 mm area. The instrument uses a scanning tunneling microscope to probe the surface topography, and a Michelson interferometer system to measure the lateral probe movement, both having sub-nanometer resolution. The lateral position is servo controlled, based on the interferometer readings, using a digital signal processor. The instrument environment includes temperature control, a vacuum system with a base pressure below 10@super -5@ Pa, and seismic and acoustic vibration isolation. Several artifacts have been measured to validate the instrument performance. Initially, an average pitch measurement was made on a grating that was produced by laser-focused atomic deposition of Cr.@footnote 1@ The average line pitch for this grating was measured to be 212.69 nm, with an estimated fractional standard uncertainty of 25 x 10@super -6@. This estimate was derived from a consideration of the sources of uncertainty for a 1 mm point-to-point measurement, including the effects of interferometer and sample alignments, Abbé errors, motion cross-coupling, and temperature variations. Most recently, M@super 3@ measurements were made of the surface lattice parameters of a conducting organic crystal and compared to the bulk lattice constants as determined by x-ray crystallography. In initial small-area measurements, the lattice constants of nominally 1.02 nm and 750 pm were in agreement to within 70 pm. These data represent a major achievement in performing a direct, real-space measurement of crystal lattice parameters using ultra-high accuracy interferometry. @FootnoteText@ @footnote 1@ J.J. McClelland, R.E. Scholten, E.C. Palm, and R.J. Celotta, "Laser Focused Atomic Deposition," Science, Vol. 262, pp. 877-880, 1993.