Imaging Technology Group Visualization, Media and Imaging Laboratory Microscopy Suite

1
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite
Magnetic and Electric Force Microscopy
Beckman Institute for Advanced Science and
Technology
Dr. Janelle Gunther, Beckman STM and ACS group
www.itg.uiuc.edu
2
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite
General AFM
Beckman Institute for Advanced Science and
Technology
A probe slides across the sample surface and is
deflected as it encounters topography
www.itg.uiuc.edu
3
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite
Tapping Mode AFM
Laser beam
Beckman Institute for Advanced Science and
Technology
Return signal
The probe is driven with the same energy Height
or material characteristics cause the probe to
deflect as it comes in contact with the sample.
A probe is oscillated at its resonant frequency.
The reflected laser beam is deflected into a
photodiode detector. This process generates a
sinusoidal electronic signal.
www.itg.uiuc.edu
4
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite
Contrast Mechanisms
Beckman Institute for Advanced Science and
Technology
www.itg.uiuc.edu
5
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite
Contrast Mechanisms
Beckman Institute for Advanced Science and
Technology
Amplitude, Phase, Frequency Phase and
frequency changes offer Better signal to noise
ratios Reduced artifacts Frequency modulation
can give quantitative information on
force gradients
www.itg.uiuc.edu
6
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite
Interleaved Imaging
1) The probe maps the surface topography on the
first pass (trace) 2) The topography is mapped
out again, but in the opposite direction
(retrace) 3) The probe is raised to a
user-specified height above the surface 4) and
5) The original topography maps are used to scan
the probe at the given height above the sample
surface. During the scan, The probe responds to
changes in magnetic properties of the sample
Beckman Institute for Advanced Science and
Technology
www.itg.uiuc.edu
7
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite
Magnetic Force Microscopy
Requirements 1) Tapping Mode 2) Interleave
scanning 3) MFM Probes Etched
silicon Magnetically sensitized by sputter
coating with a ferromagnetic material.
Beckman Institute for Advanced Science and
Technology
www.itg.uiuc.edu
8
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite

• Magnetic Force Microscopy

100x100 mm image of the magnetic tracks on a
ZipDisk Variations in the resonant frequency of
the probe were used to create contrast in the
image.
Beckman Institute for Advanced Science and
Technology
www.itg.uiuc.edu
9
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite

• Magnetic Force Microscopy

Beckman Institute for Advanced Science and
Technology
10x10 mm images of a ZipDisk Left image
height mode measures topography Right image
frequency image maps the change in resonant
frequency of the probe
www.itg.uiuc.edu
10
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite

• Magnetic Force Microscopy

100x100 mm image of a ZipDisk exposed to a
magnetic Field. Contrast mechanism Change in
the probes Resonant frequency
Beckman Institute for Advanced Science and
Technology
www.itg.uiuc.edu
11
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite

• Magnetic Force Microscopy

Beckman Institute for Advanced Science and
Technology
50x50 micron image of a sample of terfenol Left
topography Right MFM image, phase
contrast Image courtesy of Frits Brouwer
www.itg.uiuc.edu
12
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite

• Magnetic Force Microscopy

Beckman Institute for Advanced Science and
Technology
12x12 micron MFM/phase contrast image of a sample
of terfenol Image courtesy of Frits Brouwer
www.itg.uiuc.edu
13
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite

• Electric Force Microscopy

1) The probe maps the surface topography on the
first pass (trace) 2) The topography is mapped
out again, but in the opposite direction
(retrace) 3) The probe is raised to a
user-specified height above the surface 4) and
5) The original topography maps are used to scan
the probe at the given height above the sample
surface. During the scan, The probe responds to
changes in electrical influences.
Beckman Institute for Advanced Science and
Technology
www.itg.uiuc.edu
14
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite

• Electric Force Microscopy

Beckman Institute for Advanced Science and
Technology
Electric Field Gradient Imaging Measures
variations in the electric field gradient above a
sample Sample can be conducting,
non-conducting or mixed. Surface topography can
affect the experiment.
Surface Potential Imaging Measures the effective
surface voltage of the sample by adjusting the
voltage on the tip so it feels a minimum
electric force from the sample. Samples can be a
mix of conducting and non-conducting
regions. Different materials will show
contrast due to contact potential differences.
www.itg.uiuc.edu
15
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite

• Electric Force Microscopy

Beckman Institute for Advanced Science and
Technology
Topographic image (left) and surface potential
image (right) of interdigitated metal lines
(TiPtAu on Si3N4 on GaAs). The different
shadings indicate different voltage levels. 90
µm scan. Sample courtesy of Arnold Howard,
Sandia National Labs, New Mexico.
www.itg.uiuc.edu
16
Imaging Technology Group Visualization,
Media and Imaging Laboratory
Microscopy Suite

• Electric Force Microscopy

Beckman Institute for Advanced Science and
Technology
Topographic image (left) and surface potential
image (right) of interdigitated metal lines
(TiPtAu on Si3N4 on GaAs). The different
shadings indicate different voltage levels. 90
µm scan. Sample courtesy of Arnold Howard,
Sandia National Labs, New Mexico.
www.itg.uiuc.edu