Technical information

Table Of Contents

13. PROCEDURES FOR IMAGING OF STANDARDS AT

ATOMIC-SCALE RESOLUTION USING THE DIGITAL

INSTRUMENTS MULTIMODE AFM

Ortiz Nanomechanics Laboratory@MIT F01

I. Sample Producers and Preparation

•

Muscovite Mica

is a yellowish, light-colored, transparent to translucent silicate (subclass : phyllosilicates)

mineral with the following chemistry : K

(OH,F)

, Potassium aluminum silicate hydroxide

fluoride. It is a hard, layered, crystalline (monoclinic 2/m) material that fractures along weak atomic planes

("cleavage" planes), thus easily producing atomically flat surfaces of atoms having a regular lattice structure

which are excellent for use in high-resolution AFM piezo calibration and as substrates for imaging of biological

samples. Muscovite has a layered structure of aluminum silicate sheets weakly bonded together by layers of

potassium ions. The potassium ions occupy large holes between 12 oxygen atoms, 6 from the layer above and 6

from the layer below; the resulting K-O ionic bonds are rather weak and easily broken. The cleavage sheets

fairly flexible and elastic, hydrophilic, and negatively charged in water. Muscovite Mica has low iron content is

a good electrical and thermal insulator. More detailed information on Muscovite Mica can be found here :

http://www.2spi.com/catalog/submat/mic_shet.html

(*http://www.ill.fr/dif/3D-crystals/layers.html)

Another typical AFM substrate is Highly Ordered Pyrolytic Graphite (HOPG) which is described in detail

here : http://www.2spi.com/new/hopgsub.html

• A few suppliers include the following companies :

1) Bioforce Lab (

http://www.bioforce.com

)

2) Structure-Probe Inc. (*http://www.2spi.com/catalog/afmstm.html),

3) Microscopy Mart / Pelco International (*http://www.pelcoint.com/AFM.htm)

• Cleavage directions are detailed here : http://www.2spi.com/catalog/submat/mica-disk.html

• Attach to metal puck and then to piezo scanner cap.

II. Real Time Parameter Settings

• contact mode, air or fluid cantilever holder (it is typically much easier to obtain images in water or buffer than

in air)

• use stiffest spring constant cantilever; on DI V-shaped cantilever chips this is the shortest one with fattest

legs