Re: More on A.pellucida

On 23 Jan 2007 01:59:25 -0800, "rene" <renevanwezel@xxxxxxxxxxx>
wrote:



Last comment, the use of contrast enhancement techniques like
oblique/single sideband/DIC/phase contrast makes it even more
subjective. Only brightfield will show the quality of an optical
system. As you say, the resolution is there, no problem, but without
contrast (by the optical system OR the test specimen), you cannot see
it.

Oh yes, and be careful with taking sizes from SEM, in respect of tilted
valves, also SEM calibration. I wouldn't trust my own SEM pics from
A.p. within 10%. I'm sure Gary's FESEM would be better in that respect.

René.

A coated specimen will increase LM contrast. Done right, you won't
see the coating. Au is not good. Au/Pd, Ir, Pt or Pd are IMO better.
The surfaces are coated thicker than the pores due to plasma flux
variations (more difficult to get into the holes the same as the flat
surfaces).

The tilted specimens were optimal for thickness measurement. These
specimens were the internal (concave) view rather than the external
(convex) view. AP is like a W-shaped specimen with the middle of each
side flat on the cover slip. So, if one considers one side, it is
like a U where the bottom of the U is flat on the cover slip. This
allows for contrast variation between the slip and specimen. Tricky
but doable.

I use Geller MRS-5 microscopy calibration standard but only up to
500KX. The standard has patterns at 80nm (+- 1nm) on up to 3um. Most
of my work is between 5KX and 300KX. Since calibration correction is
electronic, it is easy to check and tweak if necessary. Typical
calibration limits are around +- 1% of FS at high mag and about 2-4%
at low mag (due to inability to put the cursors exactly on the edges).
So, this is mostly an operator problem.

gg


Kiss French. Drink California.
.