1. Department of Electronics
Nanoelectronics 09
Atsufumi Hirohata
Department of Electronics
13:00 Monday, 13/February/ (P/T 006)

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 *

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 * **

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 : *

7. Si (111) 7  7 Surface Reconstruction*

8. Scanning Tunnelling Spectroscopy (STS)
In order to measure a density of states (DOS) with a STM tip, *

9. Atom Manipulation
An individual atom can be manipulated by a STM tip shown by Donald Eigler in 1989 :
35 Xe atoms * **

10. Atom Manipulation by IBM

11. Atom Manipulation by IBM

12. Atomic Force Microscope (AFM)
In 1985, Gerd Binnig invented atomic force microscopy :
 Non-conductive surface can be observed. *

13. 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). ** 13

14. AFM / MFM Images MFM images can subtract dots morphology :
20 nm thick Fe dots (1 µm diameter)
30 nm thick NiFe dots (5 µm) 14

15. 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 * **

16. Early TEM Images Early oxide replica of etched Al : Si-Fe :* 16

17. Scanning Electron Microscope (SEM)
In 1937, Manfred von Ardenne developed a scanning electron microscope : * **

18. Early SEM Images SEM image of etched brass :* 18

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

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

21. Photo-emission electrons
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
(AES)
Auger electrons
Sample
Auger electrons are found by Lise Meitner in 1922 and Pierre V. Auger in 1925 : * **

22. Auger Electron Spectroscopy (AES)
Penetration depth : *
AES signal :
Co2CrAl Al Cr Co
AES mapping : ** * ** 22

23. 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

24. EPMA Signals
Example of Co2TiSn : 24

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

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

27. Surface Analysis Major techniques for surface analysis :
Incident beam
Signals
Composition
Structure
Electronic state
Auger electron spectroscopy (AES)
Electron-beam
Auger electrons
Qualitative analysis
Auger electron spectra
Auger electron diffraction (AED)
Auger diffraction
(~ a few atoms)
Electron probe micro-analyzer (EPMA)
Characteristic X-ray
Qualitative analysis (sensitivity ~ 0.1 %)
X-ray spectra
Energy dispersive
X-ray analysis (EDX)
X-ray photoelectron spectroscopy (XPS)
Photo-emission electrons
Atomic binding energy
Photoemission electron microscopy (PEEM)
X-ray / photon
Atom mapping
Secondary ion mass spectroscopy (SIMS)
Secondary electrons
Electron energy-loss spectroscopy (EELS)
Surface absorption spectra
Reflection high energy diffraction (RHEED)
Reflected electron-beam
Reflected diffraction patterns
Low energy electron diffraction (LEED)
Back-scattered diffraction patterns
X-ray absorption fine structure (XAFS)
X-ray
X-ray diffraction (XRD)
Reflected X-ay
X-ray diffraction
Transmission electron diffraction (TED)
Transmission electrons
Diffraction patterns
(t < 30 nm)
* D. P. Woodruff and T. A. Delchar, Modern Techniques of Surface Science (Cambridge University Press, Cambridge, 1994).

28. Detection Limits of Surface Analysis* 28