areas double exposed
Added by Amedee des Georges almost 10 years ago
Hello everyone,
First, happy new year! First post of the year! :-)
I have noticed on one of my datasets that a very significant portion of my micrographs came from previously exposed holes.
They have therefore twice the accumulated dose, sometimes three times. And I realized that it was not infrequent. It is about 1/4 to 1/3 of my dataset.
I welcome suggestions as to how to mitigate this. The first thing that comes to my mind is using a higher mag for the hole mode so that only one hole is present on the image, even when off center.
As I don't expect the problem to completely go away, I would like to shoot a high electron dose at the areas exposed just after collecting my exposures, so that the area is blasted and can be immediately recognized as such if exposed a second time. How can i do that without burning my K2 and without recording an extra image?
By advance, many thanks!
Amedee
Replies (1)
RE: areas double exposed - Added by Anchi Cheng almost 10 years ago
Regarding avoiding double exposure, the most important is to be consistent during targeting. On most scopes, the stage movement achieved at "Hole" node is consistant enough not to completely offset to the next hole if it is 2 um hole with 2 um inter-hole spacing. However, if it is at closer spacing, it is indeed harder to avoid target selection error. In general, the targeting of holes from those chosen at square level is more precise than accurate. Therefore, a good way to avoid target overlap at the next MSI scale is to pick the final targets with the same offsets.
If this is not possible, a more time consuming approach is to activate iterative navigator move in "Hole" node to increase the accuracy of the targeting at such level which will reduce error in choosing targets on them.
As to marking the exposed hole, if you have a secondary camera on the scope, you will be able to add a preset to your final exposure node to "post-expose" but it will indeed record an extra image. However, you can make the camera configuration of such preset in such a way that the image dimension is as small as the camera allows. The other trick we use is to melt and focus at a consistent offset and direction.