AVS 56th International Symposium & Exhibition
    Thin Film Tuesday Sessions
       Session TF1+SE-TuM

Paper TF1+SE-TuM12
A Slice of GLAD: Use of Focused Ion Beam Tomography to Characterize Titania Thin Films

Tuesday, November 10, 2009, 11:40 am, Room B3

Session: Glancing Angle Deposition I
Presenter: K.M. Krause, University of Alberta, Canada
Authors: K.M. Krause, University of Alberta, Canada
D. Vick, NRC National Institute for Nanotechnology, Canada
M.J. Brett, University of Alberta, Canada
Correspondent: Click to Email
Focused ion beam (FIB) tomography allows for the serial slicing and imaging of a sample volume on the order of several nanometers to microns thick. With this technique, a focused beam of ions rasters across the specimen surface, milling it layer-by-layer. In tandem, a scanning electron microscope (SEM) images the exposed surface at the removal of each individual slice. The series of SEM images can then be post-processed with custom or commercially available software to create a 3D reconstruction of the milled volume.

As FIB tomography has progressed over the years, the range of materials, structures, and size scales has been expanded. Various analysis have been carried out with FIB, including the study of how grain boundaries in Ni alloys influence crack propagation and how the geometry of buried Ge quantum dot superlatices depends on the growth of supporting materials layers [1 – 3]. In the present work we report on the use of ion beam milling and concurrent SEM imaging to probe the properties of titanium dioxide nanostructured thin films fabricated using the glancing angle deposition (GLAD) technique [4].

Our titania films are deposited at oblique angles, while substrate rotation is employed, on silicon wafers. The resultant films have a columnar structure with spacing between columns determined by the deposition angle and characteristics determined by the rotation speed and deposition rate. To support the porous GLAD films during FIB slicing, a photoresist is spun into the film and then baked, forming a heterogeneous solid. The photoresist not only provides support for the nanostructures as they are sliced, but also offers good atomic number (Z) contrast to the titania. The GLAD films are then sliced and imaged using a Zeiss NVision 40 Crossbeam® workstation. Captured images are post-processed using MATLABTM and commercially available JEOL TEMographyTM software packages.

While column morphology and geometric properties of GLAD films have been well studied, investigations of columnar structure have been limited to SEM and TEM. Here, we demonstrate that the FIB technique can be used to provide a spatially discrete view of GLAD intra-column and inner-column porosity and structure. Analysis of these properties is ongoing and current experimental results will be presented.

References

1. C. Holzpfel, W. Schaf, M. Marx, H. Vehoff, F. Mucklich, Scripta Materialia 56, 697-700 (2007).

2. E. Keehan, L. Karlsson, H.K.D.H Bhadeshia, M. Thuvancer, Materials Characterization 59, 877-882 (2008).

3. A.H. Kubis, T.E. Vandervelde, J.C. Bean, D.N. Dunn, R. Hull, Applied Physics Letters 88, 263103 (2006).

4. K. Robbie, M.J. Brett, A. Lakhtakia, Nature 384, 616 (1996).