Download Scanning Probe Microscopy

Report (Submitted to)
Dr. Aamir Razzaq
Scanning Probe Microscopy
Submitted by
Muhammad Khurram Farooqi
(CIIT/FA11/MSPHY/006/LHR)
Department of Physics CIIT Lahore
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Introduction
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Scanning Probe Microscopy
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


Scanning Probe Microscopy (SPM) is a technique
of microscopy which makes images of surfaces,
using a physical probe that scans the sample.
An image of the surface is obtained by
mechanically dragging the probe on surface of
the specimen, line by line.
SPMs are used both as standard analysis tools
and as high-level research instruments.
Historical Background
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


SPM was founded with the invention of the scanning
tunnelling microscope in 1981.
In 1986, very soon after their first publications about
the STM in 1981, the inventors of this marvellous
instrument, Gert Binnig and Heinrich Rohrer from the
IBM Research Laboratory in Rüschlikon (Switzerland),
were awarded the Nobel Prize in Physics.
Nowadays, SPMs can be found in many academic and
industrial physics, chemistry and biology laboratories.
Components
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Figure
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S.P.M Working
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Working
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The STM works like a record player…
 The principle of the STM is very simple.
 Can be compared best with that of an
old-fashioned record player.
 Just like in a record player, the instrument
uses a sharp needle, referred to as the
‘tip’, to interrogate the shape of the
surface.

Working
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But
in
contrast
with
a
normal record player, the STM tip
does not touch the surface.
 A voltage is applied between the
metallic tip and the specimen,
typically
between
a
few milliVolts (mV) and a few
Volts (V).

Working
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When the tip is far away from the surface,
the current is zero.
 The STM operates at very small distances
between the tip and the surface of only 0.5
to 1.0 nm, i.e. 2 to 4 atomic diameters.
 At these distances, the electrons can ‘jump’
from the tip to the surface or vice versa.
 This ‘jumping’ is a quantum mechanical
process, known as ‘tunneling’.

Working
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Hence the name of this microscope is
tunneling microscope.
 The tunneling process is very difficult,
which implies that the tunneling current
is always very low.
 STMs
usually operate at tunneling
currents
between
a
few picoAmperes (pA) and a
few nanoAmperes (nA).

SPM Environments
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Scanning probe microscopes can be
operated in a variety of environments.
But only four environments are
described:
 Ultra-high vacuum (UHV),
 Ambient (air),
 Liquid, and
 electrochemical (EC).

1. Ultra-high Vacuum
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The first STMs were operated primarily
in UHV to study atomically clean
surfaces.
 STM
applied to atomically clean
surfaces allows characterization of
structure,
without
the
added
complication of contamination that is
always present in air.

2. Ambient(Air)
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The easiest, least expensive, and thus most
popular environment for SPMs is ambient, or
air.
 STM in air is difficult, since most surfaces
develop a layer of oxides or other
contaminants that interfere with the
tunnelling current.
 A clean, “fresh” surface can be prepared by
peeling away older surfaces.

3. Liquid
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Liquid cells for the SPM allow operation
with the tip and the sample fully
submerged in liquid,
 It has capability for imaging hydrated
samples.
 A liquid environment is useful for a
variety of SPM applications, including
studies of biology, geologic systems,
corrosion etc.

4. Electrochemical
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Like UHV, electrochemical cells provide
a controlled environment for SPM
operation.
 EC-SPMs consist of a cell, a
potentiostat, and software.
 Applications of EC-SPM include realspace imaging of electronic and
structural properties of electrodes.


Key features include
 An
instrument that is easy to use
 Has lower operating costs.
 Minimal training time is desirable
in a multi-user facility.
 Finally, an instrument that is easy
to run will be used more—and
produce more results.
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1. User Interface
SPMs are built upon
operating systems that
allow multi-tasking.
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2. Optical Microscope
 All SPMs include optical microscopes to help
monitor.
 A good optical microscope speeds up our work.
 In optical microscope, the following features
are present:
 ♦ optical image clarity
 ♦ useful magnification range
 ♦ zoom lens
 ♦ integrated video camera
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Applications
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
One of the most versatile and at the same
time also very complex SPM measurement
technique is the optical nearfield microscopy
(Scanning Nearfield Optical Microscope,
SNOM or NSOM). This class of instruments
are used for investigation of electromagnetic
interactions (light) with a resolution below
the wavelength of the used electromagnetic
field.
Applications
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An STM can be used as a
spectroscopy tool, probing the
electronic properties of a material
with atomic resolution.
 It is used to study the local electronic
structure of the surface known as
scanning tunnelling spectroscopy
(STS).

Innovation
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If we have this instrument in our Lab then
we can scan the surface if the Electroactive
Conducting Polymers ECPs and quite easily
fine out their properties such as
 Electrical
 Mechanical
 Surface analysis etc

Types
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OM)






Contact Atomic Force Microscopy(CAFM)
Magnetic Force Microscopy(MFM)
Lateral Force Microscopy(LFM),
Electrostatic Force Microscopy(EFM),
Scanning Capacitance Microscopy (SCM),
Scanning Thermal Microscopy(STM) etc.
THANKS
The End
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