Experimental techniques in superatomic physics IV

Today Ion scattering Diffraction of x-rays, electrons, and neutrons Transmission and scanning electron microscopies Scanning tunnelling microscopy Atomic force microscopy Design of an experiment series

Ion scattering LEIS = Low energy ion scattering (< 10 kev) MEIS = Medium energy ion scattering HEIS = High energy ion scattering (~100 kev to 2 MeV) LEIS Fixed E 0, M 1, θ 1 E 1 gives M 2. A=M 2 /M 1 Ions: most often He +, Ne +, Ar +, but others are being used as well. Woodruff and Delchar, Modern Techniques of Surface Science

Ion scattering - Shadowing LEIS is extremely surface sensitive!

Losses due to electronic excitations Ion scattering - MEIS Multiple sandwich: 10 Å Au, 100 Å Al Woodruff and Delchar, Modern Techniques of Surface Science

X-ray, electron,, and neutron diffraction Electron microscopy Group 1: Review the basic theory of diffraction (Laue condition, Bragg condition, Laue condition in reciprocal space). Material: chapter 5.2 in Structural and Chemical Analysis of Materials Group 2: Give a brief account of x-ray, high energy electron, low energy electron, and neutron diffraction. Which method is used when? What are the advantages and disadvantages of each of the probes? Material: chapter 3.2.1 in Solid State Chemistry and its Applications, chapter 4.3 in Structural and Chemical Analysis of Materials, Fig. 9 of Powell & Jablonski, J. Phys. Chem. Ref. Data 28 (199) 19, Fig. 8 of Tung & Ritchie, Phys. Rev. B 16 (1977) 4302. Group 3: Give a brief account of transmission electron microscopy. Material: Structural and Chemical Analysis of Materials, pages 391-393, 404-408 Group 4: Give a brief account of scanning electron microscopy. Material: Structural and Chemical Analysis of Materials, pages 458-468, 471-472

Diffraction All images from J.P. Eberhart, Structural and Chemical Analysis of Materials, John Wiley & Sons, Chichester 1991.

X-ray,, neutron, and electron diffraction J.P. Eberhart, Structural and Chemical Analysis of Materials, John Wiley & Sons, Chichester 1991.

Inelastic mean free paths of electrons in matter Inelastic mean free path Tung & Ritchie, Phys. Rev. B 16 (1977) 4302. Powell & Jablonski, J. Phys. Chem. Ref. Data 28 (1999) 19

Transmission electron microscopy J.P. Eberhart, Structural and Chemical Analysis of Materials, John Wiley & Sons, Chichester 1991.

Example from Transmission electron microscopy: The formation of a carbon nanofiber by catalytic decomposition of methane over a Ni nanocrystal S. Helveg et al., Nature 427 (2004) 426

Example from High resolution transmission electron microscopy (use of phase contrast instead of intensity contrast only) J.P. Eberhart, Structural and Chemical Analysis of Materials, John Wiley & Sons, Chichester 1991.

Scanning electron microscopy All images from J.P. Eberhart, Structural and Chemical Analysis of Materials, John Wiley & Sons, Chichester 1991.

Scanning electron microscopy Reine Wallenberg, Lunds universitet

Scanning tunnelling microscopy Group 1: Explain how a scanning tunnelling microscope works in practice. Group 2: Explain the physical principle of electron tunnelling. Group 3: Explain the two different modes of scanning tunnelling microscopy.

Scanning tunnelling microscopy

Scanning tunnelling microscopy: Electron tunnelling Binnig & Rohrer, Nobel lecture

Scanning tunnelling microscopy: Principle Binnig & Rohrer, Nobel lecture

Scanning tunnelling microscopy: Tunnelling modes Constant height mode Binnig & Rohrer, Nobel lecture

Atomic force microscopy

Atomic force microscopy www.wikipedia.org

Atomic force microscopy Why would one want to use AFM if high resolution quite generally is easier to achieve with STM??

Physics experiments... Devise an experiment series (of course using what you ve learnt during this course) to elucidate as many characteristics of your sample as possible! Present this series to your fellow students. Take into account the nature of the sample. Motivate your choice of techniques. Explain how they work, and what kind of information you obtain!