NSC Dec. 15, Göksel Durkaya. Physics and Astronomy Department, Atlanta, GA,

Transcription

1 NSC Dec. 15, 2005 Göksel Durkaya Physics and Astronomy Department, Atlanta, GA, cover

2 Motivation Atomic Force Microscopy Applications What we do Conclusion 2/27

3 3/27

4 - OM: Optical Microscope Magnification by changing focal length of the objective lens Diffraction limited at ~/4 practically: ~400 nm NOT SUITABLE FOR NANO-SCALE IMAGING! The methods suitable for nano-scale applications >>> 4/27

5 - SEM: Scanning Electron Microscopy Investigation of electron reflection from a specimen Provides ~up to 10 nm size resolution 5/27

6 - TEM: Transmission Electron Microscopy Investigation of electron transmission through a specimen Provides ~10 nm size resolution 30µm x 30µm 6/27

7 - NSOM: Near Field Optical Scanning Microscopy Investigation of behavior of light reflected from the surface of a sample Provides ~ up to 50 nm size resolution 30µm x 30µm Single Molecule Detection Images courtesy of Paul F. Barbara 7/27

8 - STM: Scanning Tunneling Microscopy Investigation of surface topography by taking the tunnel current as reference that is built between tip and sample Provides ~ up to Angstrom size resolution! 2.5nm x 2.5nm Single Atom Defect Detection Images courtesy of Purdue Uni. 8/27

9 - AFM: Atomic Force Microscopy Investigation of surface topography by taking the deflection on the cantilever oscillations as reference Provides ~ Angstrom size resolution! 2.5nm x 2.5nm SARS Viruses Images courtesy of Mary Ng Mah Lee, Jason WM Lee 9/27

10 Advantages Disadvantages OM Optical Microscopy SEM Scanning Electron Microscopy TEM Transmission Electron Microscopy NSOM Near-Field Scanning Optical Microscopy STM Scanning Tunneling Microscopy - Easy to operate - Cheap - Resolution up to ~10nm - Resolution up to ~10 nm - Resolution up to ~50 nm - Provides optical spectroscopy - Resolution up to ~ 1 A! - Limited at ~ 400nm resolution - Only for visualizing -Energetic electron bombardment to sample -Energetic electron bombardment to sample - Sample preparation - Optical beam focusing on a very small area - Conducting sample requirement AFM Atomic Force Microscopy - Resolution up to ~ 1 A! - Operates on all types of samples and at different environments - No damage to the sample - Measures physical properties (friction, elasticity, power dissipation, electron transfer) - ATOMIC MANIPULATION! 10/27

11 Maximum size resolution values for different methods are compared 11/27

12 !"#$ 12/27

13 $% " Nobel Prize in 1986 by Binnig 13/27

14 $"$ 14/27

15 $& Atomic Imaging Silicon Atoms Si (111) 7x7 Graphite Atoms 15/27

16 $& Surface Characterization Bismuth thin film AFM images As-grown Annealed at 100C for 45 mins Annealed at 150C for 45 mins 30 nm 90 nm 16/27

17 $& Surface Characterization Bismuth thin film X-ray diffraction pattern 30 nm 90 nm 17/27

18 $& Manipulation and friction studies Lateral forces play an important role in friction studies as well as atomic manipulation. 18/27

19 $& Manipulation and friction studies Scanning tunneling microscopy single atom/molecule manipulation and its application to nanoscience and technology Saw-Wai Hlaa Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio /27

20 $& Manipulation and friction studies Portrait of Zhores Alferov, russian Nobel prize winner in Physics, AFM nanolithography image obtained by electrical local probe oxidation technique on ultrathin titanium film. Image courtesy of Alexander Alexeev, NT-MDT Co. 20/27

21 $ & ncafm for lateral force measurements Si (111) 7x7 Simultaneous lateral force and STM imaging of Si (111) -7 7 surface using sub-ångstrom oscillation amplitude AFM M. Atabak, G. Durkaya, H. Ö. Özer and A. Oral Bilkent University, Physics Department, Ankara, Turkey 21/27

22 $% Problem: SOFTNESS (damage of sample / not adhesive to surface) 1 ST Solution: 1990, Hansma > Imaging by an AFM in cryogenic environment >>> Crucial results obtained - however sample contamination problems Better Solution (2003): An AFM maps the force profile on the surface input Appropriate model Persistence Length Measurements Young s Modulus (softness measure) 22/27

23 $ ' Persistence Length Measurements of DNA: is a statistical property describing its straightness which correlates with stiffness and as a function of temperature Manipulation and patterning: study of nanofabrics (a) DNA waffles and (b) DNA barcodes are shown in these images (400 x 400 nm). The periodicity of the waffle grids in (a) is 19 nm. (Hansma et. al) 23/27

24 $ In 1998, a chromosome was dissected and imaged in ambient and in liquid buffer by an IC-AFM. 1998, Stark, AFM image of dissected chromosome 24/27

25 $( ) - Surface characterization of HPCVD grown samples - Correlation of AFM results with results of other characterization methods. point Roughness -rms (nm) Grain area (e-1 um2) /27

26 AFM: - Fundamentally a non-invasive method - Provides a size resolution up to Angstroms! - Suitable for biological applications where samples are sensitive - Some physical properties can be measured; elasticity, adhesion, friction, electron transfer - Can be used in various environments; Room temperature, Vacuum, Liquid, Low temperature - Plays very important role in nano-scale manipulation which is vital for constructing nano circuits - will play A KEY ROLE for nucleic acid and living cell studies in future 26/27

27 Thank you end