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Department of Electronics

Nanoelectronics 09. Atsufumi Hirohata. Department of Electronics. 12:00 14/February/2014 Friday (D/L 002). Quick Review over the Last Lecture. ( Field effect transistor (FET) ) :. ( Drain ) current increases with increasing a ( gate ) voltage. *. ON. OFF.

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Department of Electronics

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  1. Nanoelectronics 09 Atsufumi Hirohata Department of Electronics 12:00 14/February/2014 Friday (D/L 002)

  2. Quick Review over the Last Lecture ( Field effect transistor (FET) ) : ( Drain ) current increases with increasing a ( gate ) voltage. * ON OFF ( Esaki Tunneling diode ) : ( Single electron transistor (SET) ) : p n * http://stc-mditr.org/research/lsoe/highlights/highlight4.cfm

  3. Contents of Nanoelectonics I. Introduction to Nanoelectronics (01) 01 Micro- or nano-electronics ? II. Electromagnetism (02 & 03) 02 Maxwell equations 03 Scholar and vector potentials III. Basics of quantum mechanics (04 ~ 06) 04 History of quantum mechanics 1 05 History of quantum mechanics 2 06 Schrödinger equation IV. Applications of quantum mechanics (07, 10, 11, 13 & 14) 07 Quantum well V. Nanodevices (08, 09, 12, 15 ~ 18) 08 Tunnelling nanodevices 09 Nanomeasurements

  4. 09 Nanomeasurements • Scanning tunnelling microscope • Scanning tunnelling spectroscopy • Atom manipulation • Atomic force microscope • Transmission electron microscope • Scanning electron microscope • Surface analysis

  5. Scanning Tunnelling Microscope (STM) In 1982, Gerd Binnig and Heinrich Rohrer invented scanning tunnelling microscopy : Au (001) surface : tunnelling current * http://www.wikipedia.org/ ** http://nobelprize.org/

  6. Si Surface Reconstruction Atomic resolution by STM was clearly proved by Si surface observation in 1983 : Si (111) 7  7 surface reconstruction was proposed in 1959 : * http://www.omicron.de/

  7. Scanning Tunnelling Spectroscopy (STS) In order to measure a density of states (DOS) with a STM tip, * http://www.physics.berkeley.edu/research/crommie/research_stm.html

  8. Atom Manipulation An individual atom can be manipulated by a STM tip shown by Donald Eigler in 1989 : 35 Xe atoms * http://www.wikipedia.org/ ** http://www.physics.berkeley.edu/research/crommie/research_stm.html

  9. Atomic Force Microscope (AFM) In 1985, Gerd Binnig invented atomic force microscopy :  Non-conductive surface can be observed. * http://www.wikipedia.org/

  10. Magnetic Force Microscope (MFM) In 1987, a magnetic tip was introduced to observe a magnetic stray field : *  By subtracting surface morphology, magnetic domains are observed.  Similarly, scanning SQUID † / Hall‡ microscope were developed. † C. C. Tsuei et al., Phys. Rev. Lett.73, 593 (1994). ‡ A. Oral et al., Appl. Phys. Lett.69, 1324 (1996). * Y. Martin, H. K. Wickramasinghe, Appl. Phys. Lett.50, 1455 (1987). ** http://www.veeco.com/

  11. AFM / MFM Images MFM images can subtract dots morphology : 20 nm thick Fe dots (1 µm diameter) 30 nm thick NiFe dots (5 µm)

  12. Transmission Electron Microscope (TEM) In 1933, Ernst A. F.Ruska and Max Knoll built an electron microscope : • Preliminary electron microscope ( 17) in 1931 • Improved to  12,000 in 1933 • Commercially available from Siemens in 1938 • Sample thickness : 200 ~ 300 nm • Magnetic field acts as a lens to electron-beam : Hans W. H. Busch in 1927 * http://nobelprize.org/ ** http://www.wikipedia.org/

  13. Early TEM Images Early oxide replica of etched Al : Si-Fe : * http://www-g.eng.cam.ac.uk/125/achievements/mcmullan/mcm.htm

  14. Scanning Electron Microscope (SEM) In 1937, Manfred von Ardenne developed a scanning electron microscope : * http://www.wikipedia.org/ ** http://bluedianni.blogspot.com/2008/05/scanning-electron-microscopy-sem.html

  15. Early SEM Images SEM image of etched brass : * http://www-g.eng.cam.ac.uk/125/achievements/mcmullan/mcm.htm

  16. Scanning Transmission Electron Microscope (STEM) By scanning electron-beam, TEM resolution can be improved significantly : • 0.8 Å resolution York JEOL Nanocentre

  17. Capability of STEM Annular dark field (ADF) STEM Annular bright field (ABF) STEM Incident e-beam Specimen Diffraction electrons Detector Collection of electrons with large scattering angles. Collection of electrons with small scattering angles. Observation of heavy and light atoms at the same time. Observation of heavy atoms. By STEM, H atoms were directly observed : * S. D. Findlay et al., Appl. Phys. Exp.3, 116603 (2010).

  18. Surface Spectroscopy By introducing electron-beam onto a sample surface: Incident electron-beam Characteristic X-ray Reflected electron-beam Photo-emission electrons Secondary electrons Auger electrons Auger electrons (AES) Sample Auger electrons are found by Lise Meitnerin 1922 and Pierre V. Auger in 1925 : * http://www.wikipedia.org/ ** http://auger.ung.si/agn/

  19. Auger Electron Spectroscopy (AES) AES signal: Penetration depth: * Co2CrAl Al Cr Co AES mapping: ** * http://www.phi.com/ ** http://www.jeol.com/

  20. Electron Probe Micro-Analyser (EPMA) Electron Probe Micro-Analyser (EPMA) : Incident electron-beam Characteristic X-ray (EPMA, EDX) Reflected electron-beam Incident electron beam Photo-emission electrons Secondary electrons Auger electrons Bent crystal Sample Typical penetration depth : ~ 1 µm Detector Wavelength dispersive X-ray spectrometer (WDS) (EPMA) Energy dispersive X-ray spectrometer (EDS) (EDX) Counter Roland circle

  21. EPMA Signals Example of Co2TiSn :

  22. Surface Structural Analysis Shadow edge [110] [010] 10 10 00 [110] 11 11 01 Unit cell 02 12 12 2nd Laue spots 01 11 11 1st Clean surface : Streak patterns [110] [110] 00 10 10 0th Real space : fcc (001) surface Reciprocal lattice : bcc (001) Reflection high energy electron diffraction (RHEED) : Direct spot Sample Shadow edge Incident electron beam 00 Reflected beam 01 Reflected beam Typical penetration depth : a few nm Screen

  23. RHEED Observation [110] Co2FeAl (24) GaAs (001) 1.0 nm top view (001) 2.0 nm 1 Ga  2 As 20 nm bcc [110] B2 [110] 7.5 nm 1 [100]  2 [1-10] Zinc blende a = 0.56533 nm a bcc [110] L21 side view [110] Cr or Fe Al Co c (24) unit mesh RHEED patterns of Co2FeAl grown on GaAs (001) : epitaxial L21 (clean surface) Co2FeAl (001) <110> || GaAs (001) <110>

  24. Surface Analysis Major techniques for surface analysis: * D. P. Woodruff and T. A. Delchar, Modern Techniques of Surface Science (Cambridge University Press, Cambridge, 1994).

  25. Detection Limits of Surface Analysis * http://www.nanoscience.co.jp/surface_analysis/technique/RBS-HFS-PIXE-NRA.html

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