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

Paper NS-WeP5
Influence of Secondary Tip Shape and Imaging Mode on Illumination Mode NSOM Images

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: S.J. Stranick, National Institute of Standards and Technology
Authors: S.J. Stranick, National Institute of Standards and Technology
C.E. Jordan, National Institute of Standards and Technology
G.W. Bryant, National Institute of Standards and Technology
R.R. Cavanagh, National Institute of Standards and Technology
L.J. Richter, National Institute of Standards and Technology
Correspondent: Click to Email
We report illumination-mode near-field optical microscopy images of individual 80-115 nm diameter Au particles with metal-coated fiber probes. It is found that the images are strongly influenced by the thickness of the metal coating. Theoretical models are presented which are in good agreement with the images. Wide probes with thick coatings (~lambda/2) produce images consisting of three extrema, due to a resonance-like polarization of the probe end. Narrow probes with thinner coatings produce wavy images, due to interference between the direct radiation from the tip and propagating tip fields scattered by the particles. Additionally, we have demonstrated a method for acquiring images that allows for the construction of three different imaging modes from one data set: constant-gap, constant-height, and constant-intensity. The method is based on the acquisition of topographic and optical data in a three-dimensional rather than a two-dimensional scanning format with controlled scans along the dimension normal to the surface. In this way, we acquire the topographic features of the sample surface as well as its optical response at various heights. This allows for the construction of constant-height and constant-gap images from the same data set and provides a means of identifying and correcting features that are a result of topographically induced optical contrast. Comparison between images recorded in this format to images 'lift-off' corrected by a single or small number of retraction curves indicates significant artifacts can still be present in corrected images.