1. AFM

5. The cantilever holder

6. The cantilever dimensions Tip position

7. SEM image of the AFM tip

9. Typical Features of our AFM indirectly, from phase information Chemical composition 3D / 2piImage information noOblique view max 3 µmSample height ~0.03 nm Lower limit resolution 64 to 1024 pixelsResolution per image up to 100 x 100 µm 2 Working area ambient temperature and pressure Working environment

10. mirror computer system feedback system positioning system probe tip sample piezo-electric scanner PSPD Laser diode z y x hardware components of the AFM

11. Inter-atomic force vs. distance curve Non-contac t contact distance tip to sample separation repulsive forces attractive forces Intermittent- contact Force

12. Modes of operation of an AFM Contact mode Non-contact mode ƒ’ = the force gradient between tip and sample k eff = effective spring constant ω = 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 α r -1 2. Energy interactions between permanent dipole u α r -6 3 energy interactions between an ion and a dipole it induced in another molecule U α r -4 4 between a permanent dipole and the dipole it induced in another molecule U α r -6 5 forces between neutral atoms/molecules U α 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 α r -9 to α r -12 potential. Van der waals interactions arise from 2, 4, and 5.

17. Image processing Plane levelling Filtering Measuring particle sizes

18. 2D Topography Image – Aerosol Particles 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

20. Particles from stage 6 3.78 µm

21. (x’,y’) image i(x,y) Minimum separation Raised tip t(x-x’,y-y’)Tip Sample s(x,y) Tip Characterization