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Scanning Tunneling Microscopy (STM)

Basic STM Operation

178 Dimension 3100 Manual Rev. D

4. Plug the loaded tip holder into the end of the Dimension head, then mount the head into the

dovetail slot. Select Stage > Locate Tip to find the end of the STM probe—it will resemble

a metallic bee stinger. Once the tip has been located, proceed with using the Stage > Focus

Surface controls to position the sample beneath the probe.

Note: Using the microscope’s optical system, the tip will be difﬁcult or impossible to

view if it is not located over a very reﬂective surface. Usually, the stage surface

is sufﬁciently reﬂective to accomplish this; however, most polished, silicon

wafers will work just as well. If the sample is dark in appearance, it may be

necessary to load it onto the stage AFTER the tip has been located using a

reﬂective background.

5. Set the Scan Controls panel parameters to the values shown below:

6. Engage the sample surface using the Motor > Engage option. The display monitor should

render an image of the sample surface immediately. Depending on the condition of the tip,

the image on the screen will be either clear or noisy. The status bar on the control monitor

shows how many microns the tip has traveled. When the tip engages with the surface and

tunneling occurs, the computer will beep and an Engaged message will appear in the status

bar.

7. Click on a scan parameter and drag the mouse to change the parameter. Lower the Integral

gain and Proportional gain (Feedback Controls panel) near zero and vary the Bias voltage

to see how the image changes. Vary the Scan size to observe how the image can be

magnified, then vary the X offset and Y offset to see how the image can be moved. Transfer

to the Channel panels, and instead of displaying an image using Height data, select Current

at the Data type field to observe image changes.

Note: Generally, the Data type ﬁeld is set to Height whenever the Dimension is used

in STM mode to image sample surfaces with large ﬁelds of view. The Current

setting is usually selected for imaging atomic features—a more difﬁcult feat for

the Dimension-series microscopes due to their much larger stages and frames.

Customers desiring to image atomic features should use Veeco’s dedicated

STM microscope, which is equipped with a much smaller, more rigid frame.

For more information, contact Veeco.

Scan Controls

Scan size:

X offset:

Y offset:

Scan angle:

Scan rate:

Number of samples:

Slow scan axis:

Z limit:

90.0 µm

0.00 nm

0.00 deg

2.44 Hz

256

Enabled

440 V

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