Help me identify this mystery structure in my SEM image?

[CFlower]

Hey all,

As the title suggests, I've found some recurring structure on an SEM image and I can't for the life of me figure out what it is. I took the image this morning.

Here she is:
http://i.imgur.com/nFuBsW2.png

Here's a larger, more zoomed out and higher res version. A few more of the mystery objects are visible.

http://i.imgur.com/gEXW4KN.jpg

I found plenty of these things. Here's some background on the sample. This was a piece of pyrex from a glass cell that contained a mixture of xenon and nitrogen gas. It also contained rubidium. The cell was continuously irradiated with 795 nm laser light, and heated sometimes up to 180 C. We washed out the rubidium by slowly reacting it with alcohol before breaking the cell open. I've been examining the cell surface looking for etching or pitting in the glass possibly caused by xenon excimers. So far, inconclusive. But I've been completely baffled by these circular structures that keep appearing. They were not present at all on a control piece of pyrex that I imaged.

Does anyone recognize this? What might it be?

Thanks!

 

[Dale]

I am not familiar with scanning electron microscopy, but the features look very similar to impact craters. Especially since they all seem to contain some central feature. Perhaps it is a surface defect due to microscopic impacts.

 

[CFlower]

Thanks for your input. I've considered that suggestion and I think it's viable. Here are some SEM images of microcratering in a similar vein that are fairly interesting. http://ccldas.blogspot.ca/2011/05/more-sem-images.html