September 2011 Americas and Asia Pacific Editions Cover Picture and Story
COVER STORY
The cover shows height and phase atomic force microscope images of Celgard® polypropylene battery separator membrane scanned with a Dimension FastScan AFM. The membrane is a highly ordered sieve, consisting of filaments a few nanometers in diameter, and larger perpendicular linkers.
This sample is challenging to image at traditional AFM scan rates and the task is more complex when scanned at higher rates to improve imaging efficiency. The difficulty comes from the combination of nm-filaments supported only at their ends, with deep trenches in-between, making the sample ideal for the evaluation of AFM performance.
In this sample, the filaments should be oriented approximately perpendicular to the scan direction, and to image the trenches the tip needs to go down tens of nm. To come back up onto the filaments the tip must not cause damaging high lateral forces. The least effect would be a blurring of the filament edges, and if permanent damage occurs, it is a good indicator of poor force control at the AFM tip.
These effects can be further judged in detail when looking at the phase image, where they are not masked by the overall topography, and loss of tracking (forces too light to stay in contact) would also become apparent in phase. The AFM images shown here display excellent force control on Celgard, at a scan rate of 22 lines per second, consistent with a gain in imaging bandwidth of >20X when compared to a standard AFM.
The improved AFM throughput enabled by the Dimension FastScan technology is expected to be game-changing for all industries relying on nanoscale information to make product critical product improvement decisions.
(Celgard is a registered trademark of Celgard LLC, and is not associated with Bruker Nano Surfaces Division.)
Contact:
Bruker Nano Surfaces Division
www.Bruker.com/fastscan
