1. Scanning Tunneling Microscope
In The Name of Allah
Scanning Tunneling Microscope
Pooria Gill
PhD of Nanobiotechnology

2. Image from an STM
Iron atoms on the surface of Cu(111)

3. Microscopy Optical Microscopy Scanning Electron Microscopy
Scanning Probe Microscopy

4. Scanning Probe Microscope
Atomic Force Microscope (AFM)
Electrostatic Force Microscope (EFM)
Magnetic Force Microscope (MFM)
Scanning Tunneling Microscope (STM)
Near-field Scanning Optical Microscope (SNOM)

5. History
The scanning tunneling microscope was developed at IBM Zürich in 1981 by Gerd Binning and Heinrich Rohrer who shared the Nobel Prize for physics in 1986 because of the microscope.
Gerd Binning
Heinrich Rohrer

6. Scanning Tunneling Microscope (STM)
The STM is an electron microscope that
uses a single atom tip to attain atomic resolution.

7. SPM Systems
Piezoelectric Scanner

8. General Overview An extremely fine conducting probe is held
about an atom’s diameter from the sample.
Electrons tunnel between the surface and the tip,
producing an electrical signal.
While it slowly scans across the surface,
the tip is raised and lowered in order to keep
the signal constant and maintain the distance.
This enables it to follow even the smallest
details of the surface it is scanning.

9. The Tip As we will see later, is very important that the
tip of the probe be a single atom.
Tungsten is commonly used because you can use
Electro-chemical etching techniques to create
very sharp tips like the one above.

10. Quantum Tunneling
The second tip shown above is recessed by about two atoms and thus carries about a million times less current. That is why we want such a fine tip. If we can get a single atom at the tip, the vast majority of the current will run through it and thus give us atomic resolution.

11. Note A STM does not measure nuclear position directly.
Rather it measures the electron density clouds on the surface of the sample.
In some cases, the electron clouds represent the atom locations pretty well, but not always.

12. Converse Piezoelectricity
Piezoelectricity is the ability of certain crystals to produce a voltage when subjected to mechanical stress.
When you apply an electric field to a piezoelectric crystal, the crystal distorts. This is known as converse piezoelectricity. The distortions of a piezo is usually on the order of micrometers, which is in the scale needed to keep the tip of the STM a couple Angstroms from the surface.
Electric Field
Pizos
The tip

13. Advantages of Scanning Probe Microscopy
The resolution of the microscopes
Create small structures nanolithography
Do not require a partial vacuum
Disadvantages of Scanning Probe Microscopy
The detailed shape of the scanning tip
Slower in acquiring images
The maximum image size

14. Scanning Modes
STM Constant Current Mode

15. STM Constant Height Mode

16. System Components Mechanical Parts Electronics Parts
Computer + software

18. Needle replacement Needle type Platinum-iridium (PtIr) Tungsten tips
Gold
Needle preparation
Electrochemical etching
Mechanical shearing

19. System Software Execution

20. Sample preparation

21. ZnO Nanoparticles around 6.5-8nm

22. Gold Nano crystals 6-14nm

23. Gold Nano crystals 6-14nm

24. Gold Nano crystals 6-14nm

25. Calibration

26. Etching of atoms and molecules from the surface of gold (100x100nm) by our STM system
(a step for Nanorobotics)

27. Atomic resolution of graphite
4x4x 0.2nm

28. Atomic resolution of graphite

30. References
Pooria Gill, Bijan Ranjbar, Reza Saber. Scanning Tunneling Microscopy of Cauliflower-like DNA Nanostructures Synthesized by Loop-mediated Isothermal Amplification. IET Nanobiotechnology 2011; 5 (1), 8-13.
Reza Saber, Saeed Sarkar, Pooria Gill, Behzad Nazari, Faramarz Faridani. High Resolution Imaging of IgG and IgM Molecules by Scanning Tunneling Microscopy in Air Condition. Scientia Iranica (Transaction F: Nanotechnology) 2011; 18 (6), 1643–1646.
M.Q. Li. Scanning probemicroscopy (STM=AFM) and applications in biology, Appl. Phys. A 68, 255–258 (1999).
Errez Shapir et al., High-Resolution STM Imaging of Novel Single G4-DNA Molecules, J. Phys. Chem. B, Vol. 112, No. 31, 2008.
D. P. ALLISON. Immobilization of DNA for scanning probe microscopy, Proc. Nadl. Acad. Sci. USA, Vol. 89, pp , November 1992.
Hiroyuki Tanaka. Visualization of the Detailed Structure of Plasmid DNA, J. Phys. Chem. B , 112, 16788–16792.
Hiroyuki Tanaka. High-resolution scanning tunneling microscopy imaging of DNA molecules on Cu(111) surfaces, Surface Science 432 (1999) L611–L616.
Handbook of microscopy for nanotechnology / edited by Nan Yao. Zhong Lin Wang Kluwer Academic Publishers.
Scanning probe microscopes : applications in science and technology / K.S. Birdi by CRC Press LLC.
SCANNING PROBE MICROSCOPY, 2007 Springer Science+Business Media, LLC.

31. Thanks for your Attentions