[3dem] recomendation for high resolution coater

[Farzad]

Dear Marcia,

Should you want to enhance the resolution of the secondary electron images
this message works for you. Since I am a materials scientist please
consider these notes critically. These methods might be harmful to your
samples or alter the validity of the results.

A high-resolution coating means having a very thin, even, fine-grained
coating without any agglomerated coating material. The following approaches
could be helpful:

1- the coating material:

Some conductive coating materials offer higher evenness. For example, Pt
group materials offer more even and finer-grained coating, and amongst all
Osmium gives the best results. Please note that gold has higher SE yield so
do not expect high contrast bright images from a Pt or Os coating.

2- the coater:

There are many instrument-related parameters to reduce the graininess of
the coating.

2-a- Most important parameter is the vacuum. Higher the vacuum, better the
coating quality. For example, the coaters equipped with a TMP or DP offer
much lower coating roughness. Please note: high vacuum coaters are slower
and need more maintenance and vacuum technology knowledge.

2-b- The other coater-related parameter is coating speed and evaporation
rate (or sputtering or ablation rate). Higher the coating rate rougher and
grainier the coating would be. One should consider the effect of coating
speed on the preparation throughput and also maybe on the stability of the
sample.

2-c- Another tricky parameter is the distance to the source. Increasing the
distance increases the graininess to some extent then reduces it again. So
it is very tricky and it is not a straightforward parameter to play with it.

2-d- The coating source is also very important. For example, the thermal
PVDs, e.g. electron beam evaporation or even better the sublimation sources
yield a very smooth surface but they are directional and make shadows
behind the topographical protrudes.

There are also some CVD methods in the literature but I never tested them.
All the abovementioned considerations are about the PVD methods.

Should you need any other question please do not hesitate to contact me.

Best regards

Farzad Hamdi, Dr.-Ing
Scientist,
Kastritis Laboratory for Biomolecular Research Interdisciplinary research
center HALOmem, Institute of Biochemistry and Biotechnology, Biocenter,
Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
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On Sun, Aug 30, 2020 at 11:37 PM Marcia Attias <mattias at biof.ufrj.br> wrote:

> Dear colleagues,
> would you have recommendations  pro or against a particular sputter coater
> for high resolutions FE-SEM?
> Thank you in advance.
> Marcia Attias
>
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> 3dem at ncmir.ucsd.edu
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