stm / afm images

STM / AFMSTM / AFMImages Images

Explanations fromExplanations fromwww.iap.tuwien.ac.at/www/surface/STM_Gallery/stm_schematic.htmlwww.iap.tuwien.ac.at/www/surface/STM_Gallery/stm_schematic.html

www.almaden.ibm.com/vis/stm/lobby.htmlwww.almaden.ibm.com/vis/stm/lobby.htmlwww.nanoscience.com/education/STM.htmlwww.nanoscience.com/education/STM.html

Scanning Tunneling MicroscopyScanning Tunneling Microscopy

In 1981, the Scanning Tunneling microscope In 1981, the Scanning Tunneling microscope was developed by Gerd Binnig and Heinrich was developed by Gerd Binnig and Heinrich Rohrer – IBM Zurich Research Laboratories in Rohrer – IBM Zurich Research Laboratories in Switzerland (Nobel prize in physics in 1986). Switzerland (Nobel prize in physics in 1986).

This instrument works by scanning a very sharp This instrument works by scanning a very sharp metal wire tip over a sample very close to the metal wire tip over a sample very close to the surface. By applying an electric current to the tip surface. By applying an electric current to the tip or sample, we can image the surface at an or sample, we can image the surface at an extremely small scale – down to resolving extremely small scale – down to resolving individual atoms.individual atoms.

Quantum mechanics tells us that electrons have both wave and particle like properties.

Tunneling is an effect of the wavelike nature. The top image shows us that when an electron (the wave) hits a barrier, the wave doesn't abruptly end, but tapers off very quickly. For a thick barrier, the wave doesn't get past.

The bottom image shows the scenario if the barrier is quite thin (about a nanometer). Part of the wave does get through, and therefore some electrons may appear on the other side of the barrier.

TunnelingTunneling

The number of electrons that will actually tunnel is The number of electrons that will actually tunnel is very dependent upon the thickness of the barrier. very dependent upon the thickness of the barrier. The actual current through the barrier drops off The actual current through the barrier drops off exponentially with the barrier thickness.exponentially with the barrier thickness.

To extend this description to the STM: The barrier To extend this description to the STM: The barrier is the gap (air, vacuum, liquid) between the is the gap (air, vacuum, liquid) between the sample and the tip. By monitoring the current sample and the tip. By monitoring the current through the gap, we have very good control of the through the gap, we have very good control of the tip-sample distance.tip-sample distance.

Computer software is used to add color Computer software is used to add color and analyze the captured data.and analyze the captured data.

SCAN IMAGESCAN IMAGE

DEMONSTRATE ANALYSISDEMONSTRATE ANALYSIS

Use images from Science Express laptop.Use images from Science Express laptop.

Diffraction GratingDiffraction Grating

3-D View: Diffraction Grating3-D View: Diffraction Grating

Diffraction Grating - AnalysisDiffraction Grating - Analysis

Red Blood CellsRed Blood Cells

Red Blood Cells – AnalysisRed Blood Cells – Analysis

GraphiteGraphite

3-D View : Graphite3-D View : Graphite

Graphite - AnalysisGraphite - Analysis

Graphite - magnifiedGraphite - magnified

Graphite - magnifiedGraphite - magnified

Graphite - magnifiedGraphite - magnified

Graphite – magnified – AGAIN!Graphite – magnified – AGAIN!

Graphite – magnified – AGAIN!Graphite – magnified – AGAIN!

Graphite – magnified – AGAIN!Graphite – magnified – AGAIN!

Purdue UniversityPurdue UniversityPhysics DepartmentPhysics Department

http://www.physics.purdue.edu/nanophys/stm.htmlhttp://www.physics.purdue.edu/nanophys/stm.html

Atomically flat gold film.

Atoms of Highly Oriented Pyrolytic Graphite (HOPG).

Atomic Force MicroscopyAtomic Force Microscopy

In principle, the AFM works like the In principle, the AFM works like the stylus on an old record player.stylus on an old record player.

There is actual contact between the There is actual contact between the probe tip and the sample.probe tip and the sample.

The following explanation taken from

www.chembio.uoguelph.ca/educmat/chm729/afm/general.htm

Atomic Force MicroscopyAtomic Force Microscopy

1. Laser 2. Mirror 3. Photodetector 4. Amplifier 5. Register 6. Sample 7. Probe 8. Cantilever

Atomic Force MicroscopyAtomic Force Microscopy

www.wikipedia.com

AFM IMAGESAFM IMAGES

http://jpk.com/spm/gallery1.htmhttp://jpk.com/spm/gallery1.htm

JPK INSTRUMENTSJPK INSTRUMENTS

GERMANYGERMANY

DIC (Differential Interference Contrast) image of human

lymphocyte metaphase chromosomes on microscopy

slide

dimensions 83 µm * 83 µm  

DIC (Differential Interference Contrast) image of human lymphocyte metaphase chromosomes on microscopy slide

dimensions 83 µm * 83 µm  

height image (left, 3D plot) and corresponding optical

microscope image (above, bright field) of a

moth wing scale

intermittent contact modescan field 10 µm * 10 µm

z-range 0 - 1.7 µm

height image (left, 3D plot) and corresponding optical microscope image (above, bright field) of a

moth wing scale

intermittent contact modescan field 10 µm * 10 µm

z-range 0 - 1.7 µm

Height image (left, 3D plot) and corresponding optical microscope image (above, phase contrast) of a moth's eye - region of three adjacent facets. intermittent contact mode scan field 10 µm * 10 µmz-range 0 - 6.0 µm

Atomic force microscope topographical scan of a glass surface. The micro and nano-scale features of the glass can be observed, portraying the roughness of the material.Constructed at the Nanorobotics Laboratory at Carnegie Mellon University (http://nanolab.me.cmu.edu).

……science has helped us see in fine detail…science has helped us see in fine detail…

What does the future hold?What does the future hold?