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I have been imaging a small (1um), deep hole that has been machined through a thin piece of glass. The imaging has been done using a Bioscope Catalyst AFM. I have had great success imaging the hole using ScanAsyst probes in PF-QNM mode. I am able to successfully image the hole in both air and fluid. However, because of the depth of the hole and the shape of the tip, the images display the convolution of the tip and the hole, creating the appearance of a linear slope at the hole edges (see attached).
I have also been trying to use a TESP-HAR high aspect ratio probes to enhance the image. Using these HAR probes, however, has caused the hole to appear to be "filled in"(see attached). The tip is able to image the small lip that is raised around the hole, but doesn't register the actual hole in the surface of the glass (see attached).
I have attached several images to demonstrate the difference we are seeing between thetwo tip types. Both images were taken in air, the first set using the ScanAsyst probes in PF-QNM mode and the second pair using the TESP-HAR probes in contact mode. We have also used the TESP-HAR in PR-QNM mode and get similar results. Both ScanAsyst and TESP-HAR images are of the exact same hole, acquired just minutes apart from each other. In the second pair of images (with the HAR probe) a piece of dust can be seen to the left, but I wouldn't expect this to impact the hole image.
Is there a simple explanation for why the TESP-HAR tips appear to make the hole filled in? Am I doing something wrong? Or is this what you would expect from a TESP-HAR? I have tried two different TESP-HAR tips and have gotten nearly identical results. Does anyone have any thoughts as to why this might occur?
Thank you in advance for your help!
Joshua Price
Wheaton College
ScanAsyst Probe - top view
ScanAsyst Probe - side view
TESP-HAR probe - top view
TESP-HAR probe - side view
Hi joshua,
Not sure what happened here. I assume you are adjusting your peak force for imaging AND approach accordingly as the TESP levers have a significantly higher force constant that the ScanAsyst probes that your succesfully using (40N/m vs 0.7N/m). If you don't maybe you are just breaking the whole tip off after approach. Did you try a regular TESP? I have used the SS-ISC tips with 0.7N/m spring constant with success using ScanAsyst on challenging geometrical structures.
Stefan
Hello Joshua,
Two questions:
Are you very sure we are looking at the heigt channel in the TESP-Har picture, and not a error channel (e.g. peak force error)?
If I look at the picture can it be a flattening-error, because I think the picture is flatened without excluding the features (hole end the height at the top af the picture). Is there also no hole in the "raw picture"?
I can almost not believe it is a broken tip because of the stil good resolution of the edges of the hole.
I know it is not a real answer......
Joop de Vries
Good points Joop.
Those are good points. I'm sure I had the right image, however. I've added another image without any flattening or other processing. This is with out a doubt the height channel. Clearly the hole is still flat.
And I would agree, it seems like if the tip had broken off the lip around the hole wouldn't have such good resolution. I'm still a little confused on this one. Thanks again for the help!