Dipak Paramanik

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(No Transcript)
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Scanning Probe Microscopy (SPM) Study of Surface
Modification of InP(111) Due to MeV Sb
Implantation.

• Dipak Paramanik
• Institute of Physics, Bhubaneswar

Research Advisor Dr. S . Varma
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Experimental Techniques

• SPM with Nanoscope III from Digital
  Instruments(Veeco).

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Atomic Force Microscope(AFM)
Multimode AFM
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Atomic Force Microscope
Diff-Amp.
Light Deflection System
L.D.
P.S.D.
Monitor
Cantilever
Computer
Z Axis Servo System
Sample
Z Control
PZT Scanner
X,Y-Scanning System
X,Y Control
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Scanning Probe Microscopy (SPM)
A Family of Microscopy forms where a sharp probe
is scanned across a surface and some tip/sample
interaction are monitored.

• Scanning Tunneling Microscope (STM).
• Atomic Force Microscope(AFM)

• Contact Mode
• Non-Contact Mode
• Tapping Mode

• Lateral Force
• Force Modulation
• Magnetic or Electric Force
• Phase imaging

3. Other forms of SPM
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• General AFMBeam Deflection Detection
• Used for Contact Mode, Non-contact and
  TappingMode AFM
• Laser light from a solid state diode is reflected
  off the back of the cantilever and collected by a
  position sensitive detector (PSD). This consists
  of two closely spaced photodiodes. The output is
  then collected by a differential amplifier.
• Angular displacement of the cantilever results in
  one photodiode collecting more light than the
  other. The resulting output signal is
  proportional to the deflection of the cantilever.
• Detects cantilever deflection lt1A0 .

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• Piezoelectric Scanners
• Whether they expand or contract depends upon the
  polarity of the applied voltage. Digital
  Instruments scanners have AC voltage ranges of
  220 to -220V.
• SPM scanners are made from a piezoelectric
  material that expands and contracts
  proportionally to an applied voltage.

V
- V
0 V

• In some versions, the piezo tube moves the sample
  relative to the tip. In other models, the sample
  is stationary while the scanner moves the tip.
• AC signals applied to conductive areas of the
  tube create piezo movement along the three major
  axes.

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Contact Mode AFM

• A tip is scanned across the sample while a
  feedback loop maintains a constant cantilever
  deflection (and force) .
• The tip contacts the surface through the adsorbed
  fluid layer.
• Forces range from nano to micro N in ambient
  conditions and even lower (0.1 nN or less) in
  liquids.

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Tapping Mode AFM

• A cantilever with attached tip is oscillated at
  its resonant frequency and scanned across the
  sample surface.
• A constant oscillation amplitude (and thus a
  constant tip-sample interaction) are maintained
  during scanning. Typical amplitudes are 20-100nm.
• Forces can be 200 pN or less
• The amplitude of the oscillations changes when
  the tip scans over bumps or depressions on a
  surface.

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Lateral force Microscopy

• The probe is scanned sideways. The degree of
  torsion of the cantilever is used as a relative
  measure of surface friction caused by the lateral
  force exerted on the probe.
• Identify transitions between different components
  in a polymer blend, in composites or other
  mixtures.
• This mode can also be used to reveal fine
  structural details in the sample.

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Phase Imaging

• Accessible via TappingMode
• Oscillate the cantilever at its resonant
  frequency. The amplitude is used as a feedback
  signal. The phase lag is dependent on several
  things, including composition, adhesion, friction
  and viscoelastic properties

• than lateral Identify two-phase structure of
  polymer blends
• Identify surface contaminants that are not seen
  in height images
• Less damaging to soft samples force microscopy

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Magnetic Force Microscopy

• Special probes are used for MFM. These are
  magnetically sensitized by sputter coating with a
  ferromagnetic material.
• The cantilever is oscillated near its resonant
  frequency (around 100 kHz).
• The tip is oscillated 10s to 100s of nm above
  the surface.
• Gradients in the magnetic forces on the tip shift
  the resonant frequency of the cantilever .
• Monitoring this shift, or related changes in
  oscillation amplitude or phase, produces a
  magnetic force image.
• Many applications for data storage technology.

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Cantilever And Tips for AFM
10 nm
Cantilever with the tip on its end is the main
sensing component ultimately responsible for
quality of AFM imaging.
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Different Kind of AFM Probes
Tapping mode Probe
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Different Kind of AFM Probes
Contact mode Probe
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Motivation

• InP is a key material for fibre optics and high
  speed electronics.

• Sb is an important dopant in the development of
  Field Effect Transistor and Infrared Detectors.

• MeV implantation important for producing devices
  with thick buried layers.

• Ion implantation causes morphological changes in
  surface.

• Surface properties can crucially effect device
  performance and its reliability.

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Experimental Sb Implantation in InP(111)
Beam 51Sb2 Energy 1.5 MeV Average Flux 20
nA/cm2 (dE/dx)e Se 84.99 eV/Ao (dE/dx)n Sn
158.7 eV/Ao
7o off implantation Projected Range 4977
Ao Long. Stragling 1680 Ao Lat. Stragling
1221 Ao
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Modification InP(111) Surface due to Sb
implantion
Interface

• All the imges are of scan size 10 um and Z heihgt
  75 nm.

Dose 1x1011 ions/cm2
Virgin
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Higher Doses
Dose 1x1012 ions/cm2
Dose 1x1013 ions/cm2
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More higher Doses
Dose 1x1014 ions/cm2
Dose 5x1014
ions/cm2
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Very high Dose
Dose 1x1015
Dose 5x1015
ions/cm2
ions/cm2
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Roughness Study

• Roughness increases as dose increases .

• Dose 1x1014 ions/cm2 ,maximum roughness, beyond
  that roughness slowly decreases

• Surface Roughness NOT a continuous phenomena .

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Raman Analysis

• Peaks disappear at dose 5x1013 ions/cm2

TO
LO

• This indicates sample becomes completely
  amorphised at dose 5x1013 ions/cm2 .

• Surface roughness influenced by the lattice
  damage.

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Summary

• Evoluation of Surface Roughness Studied with
  Increasing Dose.

• Surface Roughness influenced by the lattice
  damage .

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Future Plan

• Roughness study for various length scales.
• Variation of defect size with Dose.
• RBS/C and Transmission Electron Study of this
  sample.

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THANK YOU