Why Does AFM Imaging Drift Over Multiple Scans?

[ema]

Hello,
I am a newbie in AFM and do not have enough time to figure out the answer to a probably easy question:
I need to image continuously, for several times without modifying the scan settings, a relatively flat sample (+/-3 or 4nm) and I notice the following:
In CM, after a while, the deflection is drifted to (usually) higher values, fact that is modifying considerably the sample-probe interaction force. This is also visible in the images (higher or lower heights) and is destroying the sample.
Similar effects I see in TM: after taking several images the set point doesn’t remain the same any more..the pictures are getting fade and I recover them only after modifying the scan settings.
I would like to know what is the cause of these effects and if there is a way to eliminate them.

Many thanks,
ema

 

[BigJDubs]

The most likely cause of the drift you are seeing is thermal drift, which occurs when the cantilever temperature increases over time. This can be caused by the laser heating the cantilever, or a number of other factors. To help reduce thermal drift, you can use an active feedback system to keep the cantilever at a constant temperature. Additionally, you can reduce the laser power, or use a shorter laser pulse duration. Finally, you can use a cantilever with a lower thermal sensitivity.

 

[charng]

Hello Ema,

Thank you for reaching out about your AFM imaging concerns. It sounds like you are experiencing some drift in your images, which can be a common issue in AFM imaging. There are a few potential causes for this, so I will try to address them one by one.

Firstly, it is possible that the drift you are seeing is due to thermal effects. As the AFM probe scans over the sample, heat can be generated and cause the sample to expand or contract slightly, leading to a change in the deflection signal. This can be particularly problematic for soft or delicate samples. To minimize this effect, it is important to keep the scan speed and force as low as possible and to use a probe with a small tip radius.

Another potential cause of drift is due to changes in the environment, such as temperature or humidity. These changes can affect the sample and its interaction with the probe, leading to drift in the images. To minimize this, it is important to control the environmental conditions as much as possible and to allow time for the sample to equilibrate before beginning imaging.

Additionally, it is possible that the drift you are seeing is due to changes in the probe itself. Over time, the probe can wear down or become contaminated, leading to changes in its properties and behavior. It is important to regularly clean and replace your probes to ensure accurate and consistent imaging.

Lastly, it is possible that the drift you are experiencing is due to an issue with the instrument itself. If you have ruled out all other potential causes, it may be worth contacting the manufacturer of your AFM for further troubleshooting and assistance.

I hope this helps to address your concerns and provide some potential solutions. Best of luck with your imaging!