Sample Analysis

   Once a sample piece has been anodized the next step is to analyze the
resulting surface. In the manufacturing sector this process is conducted in
the context of quality assurance for the resulting product and is generally
concentrated on the depth and hardness of the oxidation layer. Special
meters have been developed to test these material properties as air and
space applications ofter require precise engineering specifications.[3]

    However in the context of nanoporous alumina templates the surface
characteristics themselves become the point of interest requiring alternate
methods of analysis. Because the aspect ratio can be on the order of a few
nanometers standard optical microscopes are not an option. Instead the
template features are resolved via Tunneling Electron Microscopes (TEM)
or Scanning Electron Microsopes (SEM) which use electron beams to pen-
etrate or back-scatter the porous array and generate a computer image of
the actual surface.[5]

    The main difference between TEM and SEM is the path of the applied
electrons.[7] TEM is used primarily to image cross sections or depth profiles
as the resulting image is generated from the electrons that tunnel through
the sample onto a phosphorous screen or CCD. With SEM the incident
electrons are scattered off the surface as the beam scans over object; a
composite image is generated via the scattered electrons with resolutions
in the sub-nanometer range.

P. D. Wallace
UAF Spring 09'
Steve's Templates