Measuring Great AFM Images: 4 Criteria

DNA imaged by TT AFM Challenging samples don't necessarily require expensive AFMs. Here's a 1 µm x 1 µm AFM image of DNA measured by a $30,000 TT-AFM.

Whether an atomic force microscope (AFM) cost $30,000 or $300,000, the validity and quality of its images depends on several important non-equipment factors. The simple truth about success with Atomic Force Microscopy is that it is generally less dependent on the equipment than it is on the operator and the environment.

Optimal operation of any AFM requires that the following four criteria be addressed:

1. Controlled Vibration Environment

It is essential to locate the AFM in a vibrationally quite environment and to use the appropriate vibration isolation cabinet or table for optimal AFM performance. Prior to imaging,users should measure the AFM's noise floor to gauge whether the AFM is placed in an appropriate location. Small changes in the AFM's location can make a big difference in results.

2. Proper Sample Preparation
The second criteria for measuring great AFM images is the proper preparation of samples. Sample preparation includes ensuring that the surface is relatively free of contaminates. Here's a link to an article with tips and tricks for removing surface contamination  from samples. If deposited structures are being imaged, these must be properly adhered to the surface and applied to the surface in the correct concentration. For more on sample preparation techniques, you may want to watch highlights from AFMWorkshop's popular AFM sample preparation seminar by Peter Eaton Ph.D. And Paul West Ph.D.

3. AFM knowledge and technique
Acquiring great atomic force microscope images requires operating the AFM correctly. Sadly, there are AFM images on websites and in publications that are actually images of artifacts, rather than images of samples. AFM users should master a few skills, including: making a careful probe approach to the sample; properly optimizing the feedback parameters used to control the motion of the probe as it is scanned; selecting the appropriate probe/cantilever for the application; and using the correct scanning mode.

4. Image processing skills
After being measured, all AFM images require some image processing. It's essential to learn an image processing software package. For example, initially the background must be removed using one of several options, next a method for displaying the image must be selected, and finally data can be extracted from the image when required. AFMWorkshop uses Gwyddion software in its AFMs, an open-source image processing software available to anyone. A free webinar on image processing techniques is offered in the Learning Center section of this website.

dirty test pattern for AFM imagingImages processed with Gwyddion: 2D grey scale image of AFM test pattern showing surface contamination
dirty test pttrn 3 D March 15 PMImages processed with Gwyddion: 3D color scale image of the same AFM test pattern with surface contamination
 

Scientists, engineers and educators who make the investment in purchasing an AFM should plan on meeting the criteria above to ensure optimal performance from their AFM and satisfaction with their investment.

AFMWorkshop offers regular AFM Training to help users with any make or model of AFM achieve success. Upcoming workshops include applications training in characterizing polymers and nanoparticles (both in April, 2015), bioapplications (imaging DNA, cells and F/D curves July 2015), and mastering advanced sample techniques (July, 2015). To view some of the images produced by AFMWorkshop's atomic force microscopes, visit our AFM image gallery.

 

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