Any material of known size and geometry can be used to visualize the AFM tip, but some material is better suited depending on the user's needs.

The following are some suggestions and sources of things which can be used for the determination of the AFM tip structure. Elsewhere are some examples of what to look for when using these standards.

Feel free to add to the list by writing to me at the address below or fill out the special form.

The sphere is probably the most extensively used geometry for tip characterization since this class is not only restricted to "true" spheres but also describes the rounded portion of most structures. Calculation of the radius is easily obtained using the equation shown provided that only the apex of the tip is used in the image, otherwise the body of the tip will be erroneously measured.

Colloidal Gold

• These are available from most any microscope supplier.
• They come in a range of small sizes (5 to 50 nanometers).
• Used to determine AFM tip radius.
• Ideally, can codeposit with material being studied.
• Ted Pella supplies a kit for the AFM (#16200).

Sources

Structure Probe Inc.
Ted Pella 1-800-237-3526
Nanoprobes

References

1. S. Xu and M.F. Arnsdorf, "Calibration of the scanning (atomic) force ficroscope with gold particles" J. Microscopy 173 (1994) pg 199

Polystyrene and Glass Spheres

• Again, available from many microscope suppliers.
• Range of sizes (50 nanometers to several microns).
• Not to be used for apex determination using above formula.

Sources

Structure Probe Inc.
Ted Pella 1-800-237-3526 Image shown
Polysciences, maker of polystyrene microspheres
Banglabs, distributor of microspheres
Duke Scientific, maker of glass and polymer microspheres
Interfacial Dynamics Corporation microspheres
ProLabo microspheres
Spherotech, Inc. microspheres

References

1. Y. Li and S.M. Lindsay, "Polystyrene Latex particles as a calibration for the atomic force microscope", Rev. Sci. Instrum. 62(11), 1991, pg2630.

Array of Spheres

• Instead of individual spheres, construct an array.
• Stable, periodicity = diameter.
• Any range of sizes.
• Not to be used for apex determination using above formula.

Sources

See above.

References

1. Y. Li and S.M. Lindsay, "Polystyrene Latex particles as a calibration for the atomic force microscope", Rev. Sci. Instrum. 62(11), 1991, pg2630.

Fabricated structures

• Sharp spikes provide direct image of AFM tip.
• Often, very little deconvolution is required.
• Assorted range of heights.
• (NT-MDT) for 1000 nm of tip (image shown).
• (EMS) "Nioprobe" - niobium film for last 5-20 nm of tip.
• (EMS) "TipCheck" - titanium characterizes the last 100 nm of tip.

Sources

Silicon-MDT Image shown
EMS, 1-800-523-5874

References

1) Ken Westra et al., "Tip Artifacts in AFM imaging of thin film surfaces", J. Appl. Phys. 74, 3608 (1993)
2) Ken Westra et al., "AFM tip radius needed for accurate imaging of thin film surfaces", J. Vac. Sci. Technol. B 12, 3176 (1994)
3) Ken Westra et al., "Effect of tip shape on surface roughness measurements form AFM images of thin films", J. Vac. Sci. Technol. B 13, 344 (1995)
4) Ken Westra et al., "The microstructure of thin films observed using AFM", Thin Solid Films 257, 15 (1995)
5) Ken Westra et al., "AFM tip radius measurement using the surface of a niobium thin film", J. Vacv. Sci. Technol. A. (accepted)

These are different from the structures above in that here the top portion is flat and not rounded. Deconvolution of the images is required.

Fabricated structures

• Indifferent to scan direction
• Two sizes are available (300 and 700 nm)
• Used for xy linearity calibration

Sources

Advanced Surface Microscopy, Inc. Image shown
Moxtek

References

None found.

These round holes have been used by us before but have problems associated with them (Ref. 1).

Fabricated structures

• Indifferent to scan direction.
• One size, no longer made (?).
• Intended for xy linearity calibration.

Sources

Formerly a free sample from Digital Instruments.

References

1. P. Markiewicz and M.C. Goh, "Simulation of Atomic Force Microscope Tip-Sample/Sample-Tip Reconstruction", J. Vac. Sci. Technol. B 13, 1115 (1995).
2. P. Markiewicz and M.C. Goh, "Atomic force microscope tip deconvolution using calibration arrays", Rev. Sci. Instrum. 66, pg3186 (1995)

"Home-made" structures

• Compression molding (Ref. 1)
• Gold coated Polycarbonate filter (Ref. 2)
• Special polymer blends (Ref. 3)
• Indifferent to scan direction
• Various sizes possible
• Random distribution (?)

Sources

Not found.

References

1. S.Y. Chou, P.R. Krauss, and P.J. Renstrom, "Imprint Lithography with 25-nm Resolution", Science 272, pg 85 (1996)
2. J. Tentschert et al., (a very big postscript file).
3. T.O. Glasbey et al., Surface Science 318 (1994) L1219-L1224.

Flat on the top and with sharp sidewalls, these can give good information on the tip shape. Unfortunately, the large size of the squares means alot of data collected is not used in the reconstruction.

Fabricated structures

• Dependant on scan direction.
• Use for xy linearity calibration.

Sources

Silicon-MDT Image shown

References

None found.

Personal note: These are rather poor for tip reconstruction (Ref. 1).

Fabricated structures

• Dependant on scan direction (eg. square or diamond image).
• Used primarily for xy linearity calibration.
• Require deconvolution procedure (Ref.2)

Sources

VLSI Standards, Inc.
Nanosensors

References

1. P. Markiewicz and M.C. Goh, "Simulation of Atomic Force Microscope Tip-Sample/Sample-Tip Reconstruction", J. Vac. Sci. Technol. B 13, 1115 (1995).
2. P. Markiewicz and M.C. Goh, "Atomic force microscope tip deconvolution using calibration arrays", Rev. Sci. Instrum. 66, pg3186 (1995)

Possible Items

• Assorted structures
• Examples: DNA - 2 nm: TMV - 15 nm
• Widely available from most microscope suppliers

Sources

None found.

References

None found.

These objects can provide an image of the tip, but often only in one direction.

Possible Items

• (IBM) Silicon Nano Edges - sharp line.
• Silicon-MDT line - Image shown
• (IBM) Flared Silicon Ridges - wide lines
• Crystal structures - eg. salt (?)

Sources

IBM Sindelfingen, Germany.
Silicon-MDT Image shown

References

None found.

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Last revised on 03-02-1999 by Peter Markiewicz

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