The document discusses scanning probe microscopy (SPM) techniques. It defines local density of states (LDOS) and artifacts. It then discusses the motivation for surface research in electrical engineering due to modern devices' dominance of surface properties. It provides overviews of SPM, atomic force microscopy (AFM), and SPM software. Modes of AFM including contact, friction, tapping, and phase are summarized.

1. Present Erfan Zaker Esfahani
Email aref_z_e@yahoo.com
Course Nanotechnology
Number 09131299216
Lecturer Dr. Monajati

2. Local density of states (LDOS) is a physical
space-resolved quantity that describes the
number of states at each energy level that are
available to be occupied. According to
crystal's structure, this quantity can be
predicted by computational methods, as for
example with density functional theory
Artifact is any perceived distortion or
other data error caused by the instrument of
observation

3. ..Terms DefinitionTerms Definition
.Motivation.Motivation
.Historical Overview.Historical Overview
.SPM Overview.SPM Overview
.AFM Overview
.SPM Software.SPM Software
.Summary.Summary

4. .Surface is the shell of a macroscopic object
(the inside) in contact with its environment
(the outside world). An interface is the
boundary between two phases. Object inside
is called bulk
.In large objects with small surface area A to
volume V ratio (A/V) the physical and
chemical properties are primarily defined by
the bulk
.In small objects with a large A/V-ratio the
properties are strongly influenced by the
surface

5. Hydrophobic effectHydrophobic effect
WaterWater
Hydrophobic materialHydrophobic material
Surface structureSurface structure
(20-100μm)(20-100μm)

6. Current flow near the surfaceCurrent flow near the surface
In modern semiconductor devices surface isIn modern semiconductor devices surface is
dominantdominant

7. LayerLayer
byby
layer …layer …
SurfaceSurface
byby
surfacesurface ……

8.  surface topography
valley, planes, hills
• physical materials behavior (conducting /
insulating)
• polarity (hydrophilic / hydrophobic)
• tribological behavior (friction on "rough" or
"smooth" surface)
• physical surface behavior (reflectivity)

9. • understanding and inhibition of corrosion
• chip manufacturing / microelectronics
• hard disks (anti-friction, ultra-smooth,...)
• biological surfaces (patterned cell growth)
• sensors (chemical, biological, electrical)
• modification of anti-reflection (displays)
• modification of wetting (inkjet printing)

10. • According to all the mentioned before our
motivation as electrical engineers for surface
research is clear. The modern physical
materials properties, in general, affected by
surface.
• Moreover, we want not only passively
receive information about the surface, but
actively affect on it topology, moving the
atoms

11. Microscopy small, – see
Scanning Probe Microscopy (SPM) is a branch of
microscopy that forms images of surfaces using a
physical probe that scans the specimen. SPM able to
receive 3D surface topography

12. Local density of states (LDOS) is a physical space-resolved quantity that
describes the number of states at each energy level that are available to
be occupied. According to crystal's structure, this quantity can be
predicted by computational methods, as for example with density
functional theory
Artifact is any perceived distortion or other data error caused by the
instrument of observation
Input transducer or sensor
Convert nonelectrical signal to electrical one
Output transducer or actuator
Convert electrical signal to nonelectrical one
Piezoceramic
Ceramic that convert electrical field to mechanical deformation and vice
versa
Piezoelectric properties
are time-depended

13. SPM Scanning Probe Microscope
STM Scanning Tunneling Microscope
AFM Atomic Force Microscope
SFM Scanning Force Microscope
FFM Force-Modulated AFM
LFM Lateral Force Microscope
MFM Magnetic Force Microscope
SThM Scanning Thermal Microscope
EFM Electrical Force Microscope

14. ActuatorActuator
SensorSensor
ComputerComputer
ProbeProbe
SampleSample

15. The blind mouse can’t see the object (sample), but
using the stick (probe), he can scan it.
Arm skin (sensor) send the received from the probe
information to the brain (computer), the computer
“see” the picture, if it need receive additional
information about the sample (decision done using
feedback), it send requirement to arm muscle
(actuator), arm carefully moves the probe to
required coordinate and vice versa

16. All of the SPM techniques are based upon scanning
a probe (typically called the tip, since it literally is a
sharp metallic tip) just above a surface whilst
between scanned surface and probe exist interaction
The nature of this chosen interaction defines a
device accessory to this or that type within the
family of Scanning Probe Microscope
The information on a surface is taken by fixing (by
means of feedback system) or monitoring of
interaction of a probe and the sample

17. Surface divided to matrix of N rows by M columns
Scanning performed row by row, as result we
receive per each couple of coordinates {xi,yj},
vector with measurement results that described
surface at this point

19. We will present scanning probe microscopes
based on two kind of iteration
1.Iteration is electrical current STM
2.Iteration is atomic force AFM/SFM
In general, as mentioned, SPM have two modes,
defined by tip movement over the surface
1.Fixed probe Z coordinate, iteration or parameter
depended on iteration monitoring
2.Fixed iteration, height change monitoring

21. Cantilever
Laser
Photo
detector

23. Cantilever is a beam supported on only one end

28. 1. Contact Mode
2. Friction mode
3. Tapping Mode
4. Phase mode

29. Contact (repulsive) mode: tip makes soft
"physical contact" with the sample, the
contact force causes the cantilever to bend
to accommodate changes in topography

30. Stoney's formula
( ) 2
2
L
E
v1σ3
δ 





⋅
−⋅⋅
=
m
k
ω
L4
ωEt
δ
F
k o3
3
=⇔==
σ is applied stress
E, v are known physical parameters
t
w
L

31. Lateral force / friction mode: AFM cantilever in
contact mode is laterally deflected in the
sample
plane due to scanning motion perpendicular
to cantilever axes, lateral deflection is
measured
and gives information on surface material
apart from topography

32. Intermittent contact: AFM cantilever is
vibrated near the surface of a sample with
spacing on the order of tens to hundreds of
angstroms
In this case the oscillator is non linear,
mathematical calculation is pretty
complicated, it is out of scope of this
presentation

33. Phase mode: AFM cantilever is vibrated near the
surface of a sample with known amplitude
frequency equal to resonance cantilever one .
Compare phase of driving signal and cantilever
response
( )
( )
( ) 





=
+⋅=
+⋅=⋅+⋅+
QF
k
arctg
ωtcosZz
FωtcosAzωzβ2z
ω
2
0
0
ϕ
ϕ



34. Image of a Si surface
imaged with a force
sensor. In the left half of
the image, the cantilever
does not oscillate, in the
right half it oscillates with
an amplitude of 0.09 nm,
yielding a double image
of every atom
Image size 3.3 nm x 3.3 nm.

36. AFM contact scanning
after scanningbefore scanning

37. • Repeat the scan to ensure that it looks the
same.
• Change the scan direction and take a new
image.
• Change the scan size and take an image to
ensure that the features scale properly.
• Rotate the sample and take an image to identify
tip imaging
• Change the scan speed and take another image

38. • User-friendly interface, basic Windows tools
• Offline simulation tool
• Calibration tool, ability to see results
• Variety of supported formats
• Control unit monitoring
• Filtering control
• Mathematical tools
• Programming tools
• 3D studio – capture and editing images and
videos in real time

39. SPM standardization has only
recently begun
as part of an effort by the
International Organization for
Standardization (ISO) !!!
25 years of scanning probe microscopy
www.nanowerk.com , 2007

40. Today, Jan 2008, 25 years of STM, UNDER DEVELOPMENT