AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Wednesday Sessions
       Session NS-WeM

Paper NS-WeM7
Growth and Characterisation of Submicrometer Regular Arrays of Pillars and Helices

Wednesday, October 27, 1999, 10:20 am, Room 612

Session: Nanopatterning
Presenter: M. Malac, University of Alberta, Canada
Authors: M. Malac, University of Alberta, Canada
R.F. Egerton, University of Alberta, Canada
M.J. Brett, University of Alberta, Canada
Correspondent: Click to Email
The fabrication of photonic bandgap structures presents one of the current challenges in microfabrication. Submicron periodic structures with a high aspect ratio are necessary to create a structure with a photonic bandgap in the visible or near infrared region. We have fabricated arrays of pillars and helices with lattice parameter down to 300nm and aspect ratio as high as 25. We utilize oblique-angle deposition onto a rotating substrate (GLAD technique) to grow our films. A square array with lattice parameter between 300 nm and 1 micrometer was patterned onto the substrate prior to film growth. The array was made using electron beam lithography based on PMMA resist followed by lift-off. The array provides preferential sites for shadowed film growth when the film is deposited onto a substrate which is oblique with respect to the arriving species. This method provides a high degree of process control and sufficient number of degrees of freedom to allow for the growth of a wide range of structures. Our microstructures were made of titanium or bismuth, chosen for the large difference in their melting points. All films were deposited onto a room-temperature substrate, implying a low adatom diffusion length for titanium (due to a low ratio of substrate temperature and melting point) but a large adatom diffusion length for bismuth (where bulk diffusion may play a significant role). The titanium pillar structures appear to be uniform along their length, the crystallite size being smaller than the pillar diameter. Regular arrays of titanium helices exhibited bifurcation within each helix, whereas bifurcation was strongly suppressed in both helices and pillars made of bismuth. The delibrate introduction of a defect into the patterned array did not have a radical effect on film growth.