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OYC
11th January 2007 - 11:03 AM
Is there anyone has experience in STM on ultrathin dielectric film? Granular structure is always observed in ultrathin (<5nm) dielectric film (e.g. SiO2, HfO2.. etc), even when the film is armophous. What do you think the granular structures are?

Also, the morphology is very much rougher (3 to 4nm) than TEM observation (<0.5nm). What could be the possible reason?

Guest
16th February 2007 - 12:52 AM
This is a good topic.

In addition to STM you can consider using AFM, including conductive mode. Leakage spots in HfO2 films have been found this way.

Amorphous films microstructure is pseudocrystalline.

The tip morphology is important for imaging, it convolves with the topology.
Zephir
22nd February 2007 - 09:49 PM
QUOTE (OYC+Jan 11 2007, 02:03 PM)
What do you think the granular structures are? Also, the morphology is very much rougher (3 to 4nm) than TEM observation (<0.5nm). What could be the possible reason?

Simply the condensation: the forces required to make particle agglomerate are much more smaller, if the constituents are already absorbed at some surface. The adsorption is the reason of catalytic phenomena, due the higher relative concentration of surfactants at the surface.
2
5th May 2007 - 02:31 AM
STM on ultrathin dielectric film is tricky. The field is diminished in the film so to compensate the tip often drives into the surface to try to drive the current up.

Use standard AFM first, because it does not depend on the film conductivity so much.

If the sample and tip are clean you should be able to avoid artifacts related to contamination but not from tip shape.
Zephir
5th May 2007 - 01:51 PM
QUOTE (OYC+Jan 11 2007, 02:03 PM)
What do you think the granular structures are?

Probably the standing quantum waves in the potential field of the tip.
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