Products and services for AFM, STM, and SEM
Applications of AFM and STM
Cast, extruded, or molded polymers
New materials including ultra high strength magnets
Optics & Photonics
of interesting images
Educational and Demonstration Experiments in Scanning Probe
At Advanced Surface Microscopy, we are very enthusiastic about AFM and we
like to say that any surface you can touch is a potential candidate for study.
The following examples emphasize common and/or relatively inexpensive materials.
Contact or Tapping Mode AFM - Height Imaging
Here are some ideas that emphasize nm- to um-scale topography
- Aluminum foil - compare shiny and dull sides. What does this tell you
about the process for making the foil?
- Salt and sugar crystals - look at facetting, defects, motion of atomic
steps over time. Does humidity affect the rate of surface diffusion?
- Paper and paper coatings - comparing cheap photocopier paper with
expensive "photo quality" paper for ink jet printers
- Polymer fibers: compare cotton and rayon. Both are made of
cellulose, but the surface structure is very different. Reading
- see Encyclopedia of Polymer
Science and Engineering to learn what cellulose and rayon are. Which
one can crystallize? Which one can only form amorphous structures?
- Hair: see the overlapping segments (like shingles on a roof).
Compare the proximal (near scalp) and distal (far end) surfaces. Does
hair wear out? Look for shampoo and/or dirt deposits.
- Magnetic hard drive. take apart a dead drive, removing the recording
head and media:
- identify and scan the pole tip region of the recording
- scan different regions of the disk surface. Why is the
- CD-R (compact disc-recordable). Remove the coating from the label
side. Image the dye-coated surface. Using alcohol or other suitable
solvent, wash off
the dye from a spot and scan the grooved surface. What is the function
this surface? Reading: Ken C. Pohlmann, The Compact Disc
- "water spots". Apply a droplet of a dilute solution, such
as tap water, to a smooth surface, such as glass.
Let dry. AFM images will often show rings of residual material.
rings form when a droplet evaporates? Reading - research papers by Sidney
Nagel and co-workers (Physics, U. Chicago.):
AT THE BREAKFAST TABLE
Rings: Solute Deposits at the Contact Line of a Drying Sessile Drop.
Tapping Mode Height and Phase Imaging
Tapping Mode height images often show higher resolution than contact mode,
because the tip is sharper and lateral forces, which deform the surface, are
practically absent. Phase imaging adds the new
capability of mapping material domains.
An intriguing specimen for demonstrating phase contrast of material domains
at high resolution (10 nm) is our Model PT-1.
Most of the materials listed for Contact Mode imaging also show phase
- Aluminum foil - apply a viscous oil and then wipe the surface, leaving
only microdroplets behind. Scans near the microdroplets should contain
some nanodroplets, which normally appear dark, indicating strong adhesion
and low stiffness.
- "Water spots"
- Hard disk drive: Different regions of the magnetic recording head
have different phase contrast.
- The Platinum-coated 10-um pitch 2-dimensional grid specimen commonly
supplied with Digital Instruments AFMs up to about 2000 often becomes
contaminated with nm-scale bumps. These show good phase
Magnetic Force Imaging
- Image the data and servo marks on magnetic recording tape or hard disks.
- Advanced: connect the appropriate leads of a magnetic recording head
to a dc power supply. Image the magnetic field at the pole tips with
and without applied current. Caution: use a resistor to limit
the current to about 1-10 mA. Hint: the appropriate leads are
the ones connected to the inductive write head. You may need a
microscope to identify these. Older recording heads are easier to work
with because everything is larger.
Electric Force Imaging
Metallic specimens with sharp edges will illustrate geometric variations in
electric force gradients. Aluminum foil or our Model
750-HD can be used.
- "Atomic Force Microscopy?, Donald A. Chernoff and Sergei Magonov,
chapter 19 in ?Comprehensive Desk Reference of Polymer Characterization
and Analysis?, R. Brady, ed., Oxford University Press, New York. 2003
This chapter describes AFM starting with the basics and continuing with
various applications so that the reader can understand each technique, the
information it provides, how to prepare the samples and capture the images,
and how to interpret the data. Although the examples emphasize
polymers, anyone examining materials with AFM can benefit. The
discussion uses very little mathematics.
- ASTM E 2382?04 ?Guide to Scanner and Tip Related Artifacts in Scanning
Tunneling Microscopy and Atomic Force Microscopy?, under jurisdiction of
ASTM Committee E42 on Surface Analysis and direct responsibility of
Subcommittee E42.14 on STM/AFM. Published by ASTM International.
September 2004. www.astm.org.
This document helps users understand how to recognize many types image
errors. Remember: all scientific instruments have artifacts.
Recognizing the artifacts is a required skill for an advanced user.