AFM

1

• AFM

2
(No Transcript)
3
(No Transcript)
4
(No Transcript)
5
(No Transcript)
6
The cantilever dimensions
7
SEM image of the AFM tip
8
(No Transcript)
9
Typical Features of our AFM
ambient temperature and pressure
Working environment
up to 100 x 100 µm2
Working area
64 to 1024 pixels
Resolution per image
Lower limit resolution
0.03 nm
max 3 µm
Sample height
no
Oblique view
3D / 2pi
Image information
indirectly, from phase information
Chemical composition
10
Laser diode
hardware components of the AFM
11
Inter-atomic force vs. distance curve
12

• Modes of operation of an AFM
• Contact mode
• Non-contact mode

the force gradient between tip and
sample keff effective spring constant ?
operational frequency m effective mass of
cantilever
13

• Theory, inter-molecular forces
• Electrostatic, (magnetic) and van der Waals
  forces
• Van der Waals forces
• Polarisation from permanent dipoles
• Induction-induced dipoles
• Dispersion-fluctuation of electrons as function
  of light

14

• Theory, inter-molecular forces
• 1. Coulombic energy between ions with net charges
  leading to a long range attraction with u a r-1
• 2. Energy interactions between permanent dipole u
  a r-6
• 3 energy interactions between an ion and a dipole
  it induced in another molecule U a r-4
• 4 between a permanent dipole and the dipole it
  induced in another molecule U a r-6
• 5 forces between neutral atoms/molecules U a r-6
• 6. Overlapping energy arising from positive
  nuclei of one molecule and the electron cloud of
  another. This overlap leads to repulsion at very
  close intermolecular separations with a r-9 to a
  r-12 potential.
• Van der waals interactions arise from 2, 4, and 5.

15
(No Transcript)
16
(No Transcript)
17

• Image processing
• Plane levelling
• Filtering
• Measuring particle sizes

18
2D Topography Image Aerosol Particles
3.535 µm
Source Topography Mode AFM Fast Scan
Direction X X scan left to right Y scan
bottom to top of columns 256 of rows
256 X scan size 3.535 µm Y scan size 3.535 µm
3.535 µm
19
(No Transcript)
20
Particles from stage 6
21
Tip Characterization