|  Using AFM for Photonics Applications
|
Atomic Force Microscopes (AFMs) are well-suited for photonics applications. This is because an AFM provides extreme contrast on flat samples, yields three dimensional images, and can examine optically transparent materials. Operationally, an AFM is a derivative of a stylus profiler; the primary difference between the two is that by using an AFM's feedback control loop, small probe/sample forces are possible.
|
Some specific areas of photonics applications are highlighted below. They include:
- Gratings
- Analysis of Polished Fused Silica Substrates
- Thin Films
Gratings
Atomic Force Microscopes scan and directly measure the topography of ruled gratings. From AFM images, the ruling angle, pitch, and surface texture of features are measurable. The images below are of of a ruled grating measured on a
|
|
|
| 4 X 4 micron color scale vibrating mode image of ruled grating. Notice the surface texture at the apex of each of the lines. Red Line above is detailed in information below. |
|
|
|
| Analysis of line profile taken from the same 4 X 4 micron vibrating mode image. Cursors 1 and 2 show that the grate angle is 19 degrees and cursors 2 and 4 show that the pitch is .376 nm. |
|
|
|
| 3-D image of the same ruled grating, displayed in color scale with a light projection. This image readily facilitates visualization of the grating's irregularities. |
|
Analysis of Polished Fused Silica Substrates
Once polished, fused silica substrates can have surface roughness values of 0.1 nm. With an AFM it is possible to visualize the surface of polished silica substrates, measure the surface texture, and measure the dimensions of structures created by the polishing process.
|
|
|
| Vibrating mode AFM image of a fused silica substrate having an RMS roughness of 0.106 nm and an Ra of 0.083nm. The scan size of the image is 1 X 2 microns. A residual polish mark is visible at the right of the image. |
|
|
|
| 1 X 2 micron AFM image of a substrate with an RMS roughness of .203 nm and an Ra of 0.159nm. Several polish marks in differing directions are visible in the image. The red line designates a line profile which allows measurement of the depth and the width of the polishing mark. The line is detailed in the graph below. |
|
|
|
| Line profile taken from the AFM image of the polished substrate having a .203 nm RMS roughness. The half width of the polish mark in the image is 19.4 nm and the depth of the feature is 0.0354 nm. |
|
Thin Films
AFM is ideal for imaging coatings used for photonics devices. Beyond visualizing the overall surface topography, measurements of grain sizes and surface texture are possible. Below is an AFM image of Indium Tin Oxide. An advantage of imaging films such as ITO with an AFM is that a vacuum is not required.
|
|
|
| TT-AFM image of Indium Tin Oxide |
|
For More Information on AFMs and Photonics along with additional AFM Application notes, we invite you to visit our website's Applications area.
|
| Brief AFM Videos Available |
UC Berkeley's Physics 111 Experimentation Laboratory is an intensive 3-unit laboratory course for 3rd- and 4th-year physics students at the University of California at Berkeley. To facilitate use of the TT-AFM in an experiment, the group has prepared some practical introductory videos including:
In addition to being informative, we nominate them for
"Best Use of Music and Star Wars Scrolling in an AFM Instructional Video."
The Regents at UC Berkeley and Don Orlando, Senior Research & Development Engineer and 111 Lab Manager, have generously made these videos available for public viewing.
|
AFMWorkshop recently posted our 20 minute AFM Image Processing Webinar on our YouTube Channel. Getting the most from your AFM requires effective utilization of image processing software. This brief seminar covers how to level images, display images, and analyze images with Gwyddion, an open source AFM image processing software. If you'd like to receive the slides from that webinar, please contact us.
|
|
|
 |
|
A still shot from animated series #2 on Vibrating Mode for AFMs
|
|
A very popular step-by-step animation series, currently includes :
|
from Oxford University Press, by Peter Eaton and Paul West. Order yours today from Amazon.com.
"...a great introduction to AFMs for beginners and also serves as a good starting point for more serious users."
Udo D. Schwarz,
Yale University
|
|
|
