Introduction to the Digital Instruments MultiMode SPM
Microscope Speci
fi
cations
Rev. B
MultiMode SPM Installation Manual
13
1.3
Microscope Speci
fi
cations
The MultiMode SPM can be
fi
tted with any of several scanners, depending upon the imaging
requirements. Generally, the smaller the scan, the smaller the scanner used. This is especially true
of atomic-scale scans, which are most often conducted with “A” or “E” scanners. Larger scans are
normally performed using “J” scanners.
1.3.1 Image Size and Resolution
Images consist of raster-scanned, electronic renderings of sample surfaces. There are three default
sizes: 128 x 128 pixels, 256 x 256 pixels, and 512 x 512 pixels. In addition, nine width-to-height
aspect ratios may be speci
fi
ed by the user: 1:1, 2:1, 4:1, 8:1, 16:1, 32:1, 64:1, 128:1 and 256:1.
Thus, it is possible to obtain “strip scans” which require less time to capture.
The controller provides 16-bit resolution on all three axes, with three independent 16-bit digital-to-
analog converters (DACs) in X and Y for control of the scan pattern, scaling and offset. This
con
fi
guration provides 16-bit resolution of the lateral scanning motion at any scan size, and the
ability to perform atomic resolution imaging throughout the full lateral range of the scanner. The
patented digital feedback is governed by integral and proportional gain controls, providing
immediate response to scanning parameter changes.
The MultiMode can scan up to 200µm laterally (in X and Y) and 10µm vertically (Z axis).
summarizes each scanner’s capabilities.
1.3.2 Scanning Techniques with the MultiMode SPM
The MultiMode is so called because it offers multiple SPM modes, including AFM, ECAFM,
ECSTM, STM and TappingMode. A complete range of Atomic Force Microscopy (AFM) and
Scanning Tunneling Microscopy (STM) techniques is available with the MultiMode SPM. Some of
these techniques are available only through Veeco.
•
Contact AFM
—Measures topography by sliding the probe’s tip across the sample
surface. Operates in both air and
fl
.
•
TappingMode AFM
— Measures topography by tapping the surface with an oscillating
tip. This eliminates shear forces which can damage soft samples and reduce image
resolution. TappingMode is available in air and
fl
uids (patented). This is now the
technique of choice for most AFM work. See
•
Phase Imaging
—Provides image contrast caused by differences in surface adhesion
and viscoelasticity. Requires a Basic Extender Module in conjunction with a NanoScope
III or IIIA controller. See
•
Non-contact AFM
—Measures topography by sensing Van der Waals attractive forces
between the surface and the probe tip held above the surface. Provides lower resolution
than either contact AFM or TappingMode.
