Veeco Dimension 3100, Manual

Page: 278 / 376

Magnetic Force Microscopy
Basic MFM Operation
258 Dimension 3100 Manual Rev. D
15.2 Basic MFM Operation
In the instructions below, steps specific to phase and amplitude imaging are described
independently. Use the icons in the margin to locate steps specific to either frequency modulation
and phase detection, or amplitude detection.
15.2.1 MFM Using LiftMode
LiftMode allows the imaging of relatively weak but long-range magnetic interactions while
minimizing the influence of topography (see Figure 15.1a ). Measurements are taken in two passes
across each scan line; each pass consists of one trace and one retrace. In the first pass,
topographical data is taken in TappingMode. The tip is then raised to the lift scan height and a
second trace and retrace performed while maintaining a constant separation between the tip and
local surface topography. Magnetic interactions are detected during this second pass. In LiftMode,
topographical features are virtually absent from the MFM image (see
Figure 15.2e ).
This section provides instructions for using the LiftMode of Interleave Scanning to obtain MFM
images. These guidelines will help you obtain an MFM image of a standard magnetic sample
(metal-evaporated video tape). Standard tape samples are provided with purchase of MFM probes,
and can be obtained free of charge from Veeco. Other samples can also be used; however, you will
not have the benefit of comparing your results with the images shown here. Obtaining a good image
of the tape sample will familiarize you with Interleave and MFM techniques and provide a check
that the system is correctly tuned to image magnetic samples. Many of the principles discussed here
also apply to Electric Force Microscopy (EFM).
As mentioned above, the NanoScope controllers use force gradient detection for MFM imaging.
Within this general technique, there are three possible schemes, known as frequency modulation,
phase detection, and amplitude detection. Phase detection and frequency modulation are available
for all TappingMode-capable microscopes in the form of the Basic Extender Electronics Module
(Basic) and Quadrex Extender Electronics Module (Quadrex). (Microscopes without an Extender
addition cannot utilize phase detection; for more information, contact Veeco.) The NanoScope IV
design integrates the Quadrex. Phase detection and frequency modulation detection are superior
methods for magnetic force imaging, offering greater ease of use, better signal-to-noise ratios, and
reduced artifact content as compared to amplitude detection. Extender electronics are strongly
recommended for extensive MFM imaging.
For MFM procedures, magnetic-coated tips are required. Various kinds of MFM probes are
available for specific applications; contact Veeco for more information. For specific information
regarding TappingMode and Interleave Scanning please refer to
Chapter 9 and Chapter 14
respectively.
The procedure below suggests parameter values that should work well for most applications.
Further adjustment, in some cases, will improve the quality of MFM scans. Some experimentation
may be needed to optimize the imaging of specific samples. See the suggestions at the end of this
section.