Made 12/01/06

Digital Instruments—model: Dimension 3100

If the right screen is not “on” it means that the program (which runs in the left screen) is in the data file mode. Click on microscope icon in upper right corner, which will bring the left monitor to the main interface screen, and the right monitor will display afm status and positions

ATTACHING TIPHOLDER

If Tip is already in the tip holder:

– Invert the AFM “head” in its V-groove slot, So the place to attach the tip holder is facing up. – Press in the tip holder onto the prongs, and then return the AFM” head” back to its non-inverted position within the V-groove

FOCUS LASER ONTO CANTILEVER

–Move the two top thumb screws for left and right movements, until you have found the tip of the cantilever in the center of the laser beam. Then move the laser over the cantilever tip so that it just barely splits the central point of the laser. This will be the approximate position of the AFM tip itself. –Watch the “sum” which is on the AFM monitor screen. We want to maximize the sum. Good values seem to be between 2-3.

FOCUS THE CANTILEVER DEFLECTION MIRRORS

–In the program panel, set “mode” into contact. This allows you to see both the horizontal and vertical deflections –move the two thumb screws on the side of the laser head, until the red dot representing the vertical and horizontal deflection is centered in the 4 quadrant window.

MOVE SAMPLE UNDER LASER

–Put sample to be AFM’ed onto the stage and turn on the vacuum –Click on the icon in the program screen, second in from the right, which is red with a magnifying glass. (This is the sample focus button, but we do not focus at this stage!) –After checking that the height of the tip will clear the sample, use the trackball to move the sample under the red laser light in the approximate position that you want to scan. –Close the focus window

DEFINE INITIAL SETTINGS

All in “program window” –Set a small scan size, say 500nm-1um –Slow scan speed, say 1 Hz. –Samples/line can be 512 or 256. number of lines 256 –Integral and proportional gains can be ~ 0.5 and 1.2 respectively (for my samples at least, std. for Scott and Luke is to set it to 0.5 and 3.0 respectively, and they just change the amplitude set point.) The following MUST be done * Mode must be in TAPPING mode * * Z limit must be at a maximum… 6.477um * * Interleave mode must be disabled *

TUNE THE CANTILEVER

This step essentially indicated the spring constant—amplitude as a function of voltage. –Use the icon in the toolbar with the tuning fork. Once this is selected Set resonant frequency range to 100-500 kHz—(this information is on the box containing the tips.) –use the auto tune setting, and this will do all of the work for you ☺ –you should see the resonant peak shift off center a bit to the right of the central axis. –There will be an “eye” in the program window. Click on it to get back to the main program window.

FOCUS ON CANTILEVER

–In the program window, click on the icon to the far right, green with a V representing the cantilever tip. This will bring up a window in the AFM monitor which shows the tip. –There are settings in which to adjust the brightness. –use the focus buttons on the trackball, to zoom and focus. –Use the two knob facing front of the AFM head to adjust the red crosshairs so that there are aligned where the tip would be. (This corresponds to the crosshairs in the left monitor screen).

FOCUS ON SAMPLE

–click again on the red icon with the magnifying glass. –use focus buttons to bring substrate into focus. –use track ball to move to the place that you want to scan

LOWER TIP!

Good Luck… Scan away!!

REAL TIME VIEWING THE SCANS

There are two channels, one height, and one can be set to amplitude. Amplitude shows the derivative of the height. This can also help when tuning the two different gains.

When scanning fast, will need to increase integral gain.

In the AFM terminal window, can move where the tip is by selection “??” which brings up crosshairs. Click on where you want the new center to be, and then click execute. Doing “execute” 2 times from right side of frame will move you one whole frame over. Watch x and y offset so that you are not missing scanning part of your sample

SETTINGS AND SCANNING KNOBS to TURN: getting better images:

– Roughly the “standard” settings with which to begin a scan with:

Integral gain 0.4 Proportional gain 3.0 Amplitude setpoint 1.4 Scan speed 1Hz

“Data Scale” : this only changes the picture that we are looking at during the scan, but does not change in any way the way the scan is being taken. But with the right parameters it may help us to locate the nanotubes better:

Standard setting: 10nm, which is standard viewing for looking for tubes as small as 2nm

“Scan size”: (This does affect what is being recorded!) typically 10um square for initial search (of unsuspended tubes). To measure the size of a tube, would want use a smaller scan size of ~ 1um square.

Amplitude setpoint: Define the distance the tip should be from the surface that it is “tapping”. (also, corresponds to the force at which it is tapping with) If the image shows as all smooth dark area, the tip is most likely not in contact with the surface, and the setpoint needs to be lowered.

If the sample is tilted, the amplitude setpoint may have to be lowered.

SAVING DATA:

Go to Camera settings and save a file that starts with your initials, then the 6 digit date. This will end in an extension with three digits after it, which will number the scans recorded for that date. Eg: on Feb 21st 2007 I recorded data into

sr022107.001 For each time you press the camera icon, the whole frame that you are in the process of scanning will be recorded. After that it will automatically iterate, eg: to sr022107.002.

If, in the middle of capturing a scan you change parameters that affect how the scan is taken, the bottom of the screen would give the capure status as : “Capture Next”. This means that it will not save the scan that you are doing, but will automatically capture the next full scan that is done, once it hits the endpoint, (either the top or the bottom). If you truly want to record the original scan, press the camera icon again, and the status will then read, “Capture Forced”

Capturing the last frame: If you forgot to capture that last frame, and you wanted it badly– Do not fear! The key sequence “control – b”, will capture the last frame.

Note: the number in the extension that is displayes : xxxxxx.001 or xxxxxx.002 represents the number of the next scan that will be taken. If this number has iterated too far, go into the files that have been saved and change that number.

ORGANIZING DATA

Since the files names do not reflect what you are doing, it is important to record in your lab book what each scan represents. A sample way to do this is:

File # sp022107.###

.001 - wafer and chip number, electrode number, sketch of area being scanned. .002 ……

ANALYZING DATA:

– The icon (spectra looking thingy) in upper right corner of program window will bring you to the saved files – go to “Image”, and select “Height info” –go to “modify” and ten “flatten” (alternately use rolling pin icon) –Execute, then quit *Now click on the knife icon (whoever wrote this program had fun for certain) –Click on image in right screen –There will be 2 red arrows. Clicking once will drag arrow wherever the cursor goes. (clicking twich will “let go” of the red arrow. As you draw the arrow around it will give the height info with respect to the other arrow. –We measure diameter of the tube by measuring the heaight at the top of the CNT. Measuring the width does not tell us about the nanotube, but it ca tell us about the resolution of the AFM tip –Quit *Click on the Microscope icon in the upper right hand corner of the window, which brings you back to the program screen. It will ask you if you want to save the changes. DO NOT SAVE CHANGES. We want to keep original data