Developing novel characterization methods for atomic force microscopy cantilever tips

1. Developing novel characterization methods for atomic force microscopy cantilever tips Thomas M. Hadley

2. Background • Atomic force microscopy (AFM) uses a sharp-tipped cantilever to image a sample surface[1]

3. Background • Convolution due to cantilever tip geometry (including cone angle and tip radius) becomes more significant with smaller surface features[2]

4. Background • At the present there are two problems: • There is no standard method for obtaining the cone angle from image data that includes uncertainty analysis • The method for calculating tip-radius is not “user-friendly” and requires experience in order to achieve accurate results

5. Hypothesis MatLAB code can be written to calculate tip radius and cone angle with uncertainty values using height data from an undercut sample.

6. Methods • AFM Imaging • Develop cone angle procedure for TGX grating • Compare tip radius procedure for TGX grating and TGT grating

7. Methods • Uncertainty Analysis • Use the methods outlined by Dunn in Measurement and Data Analysis for Engineering and Science to propagate uncertainty • Tip radius • Cone angle

8. Methods • MatLAB Coding • Cone angle with uncertainty from data obtained using the TGX01 procedure • Revise existing tip radius code to be easier to use and to include uncertainty values

9. Methods • Compare results to SEM imaging • Analyze the same tips from AFM imaging using SEM • Accuracy • Precision • Complete wear tests and observe the effect on tip radius and cone angle

10. Methods UncertaintyAnalysis Comparison toSEM AFM Imaging MatLABCoding

11. Current Status • Trained in AFM tapping mode procedure • TGX and TGT gratings are ready for imaging • In need of tapping mode cantilevers • Initial imaging can be done with contact mode tips

12. Current Status • MatLAB Coding • Learning MatLAB programming basics • Examining tip radius code • Beginning to write cone angle code

13. Timeline • Complete uncertainty analysis by 7/13 • All AFM imaging for TGX and TGT gratings completed by 7/18 • Complete MatLAB coding by 7/23

14. Conclusions & Implications • Uncertainty propagation may help to better understand tip convolution • Calculating cone angle using AFM may be more efficient than using SEM • Making the tip radius code more user-friendly may eliminate inconsistent use between users

16. References • Poggi, M.A., Gadsby, E.D., Bottomley, L.A., King, W.P., Oroudjev, E. & Hansma, H. (2004). Scanning probe microscopy. Analytical Chemistry 76(12), 3429-3443. • Villarrubia, J.S. (1997). Algorithms for scanned probe microscope image simulation, surface reconstruction, and tip estimation. Journal of Research of the National Institute of Standards and Technology 102(4), 425-454

17. Images Used • http://www.sciencedirect.com/science?_ob=MiamiCaptionURL&_method=retrieve&_eid=1-s2.0-S0304399106001665&_image=1-s2.0-S0304399106001665-gr1.jpg&_ba=&_fmt=full&_orig=na&_issn=03043991&_pii=S0304399106001665&_acct=C000040078&_version=1&_urlVersion=0&_userid=716796&md5=ed7bb225c643108257d93852847b7961 • http://upload.wikimedia.org/wikipedia/commons/0/0f/AFM_(used)_cantilever_in_Scanning_Electron_Microscope,_magnification_1000x.GIF • http://www.spmtips.com/foto/tgx01_f.jpg • http://www.kteknano.com/kteknano/calibration-gratings/tgt1.html • http://www.polymer-physics.uwaterloo.ca/images/PICTURES/equipmentpics/afm%20diagram.gif • http://www.iis.ee.ethz.ch/research/physchar/microscopy.en.html

18. Thank You