‫מבוא לננופיסיקה‬
‫המרצה‪ :‬פרופ' ברוך הורוביץ‬
‫נושאי הקורס‬
‫תכונות של חצאי מוליכים‪ ,‬הנדסה של מבנה פסים‪ ,‬אלקטרונים וחורים‪ ,‬סימום‬
‫אלקטרוסטטיקה של מבנים ננומטרים‬
‫מוליכות חשמלית‪ ,‬דיפוזיה‪ ,‬התאבכות קוונטית ולוקליזציה‬
‫מוליכות בערוצים ונוסחאות לנדאואר‬
‫אפקט הול קוונטי בשני ממדים‪ ,‬אפקט הול שבור‪ ,‬מטענים שבורים‬
‫נקודות קוונטיות‪ ,‬מחסום קולוני‪ ,‬טרנסיסטור חד‪-‬אלקטרוני‪.‬‬
‫ספר מומלץ‪:‬‬
‫בספריה)‬
‫"‪Thomas Ihn, "Semiconductor Nanostructure‬‬
‫(‪ 3‬עותקים‬
Mesoscopic systems
Moore’s law (Intel founding team)
” Transistors on one chip doubles every 18 months”
The Development of Semiconductor Industry 1.
The first transistor
W. Shockley, J. Bardeen, W. Brattain, Bell Laboratories (1947)
The first transistor
Nobel Prize, 1956.
108 transistors/chips
IBM 2003
Silicon flakes
Quartz sand
→
Si single cristal (2m x 20cm)
Lattice defects: 1000/cm3
Defect concentration: 10-12
The Development of Semiconductor Industry 2.
IC (Integrated Circuit)
CCD (Charge Coupled Device)
High Electron Mobility Transistor
600GHz max. frequency telekommunication
Semiconductor laser
Z.I. Alferov, H. Kroemer, J.St.C. Kilby – Nobel Prize 2000.
for “The Basis of Technologies of Information and Communication”
The technology of the semiconductor industry under extreme conditions
(low temperature, high magnetic field)
Actual record:
Two dimensional electron gas2DEG)
λF ≈10 −100nm
Nanostructures
Litography of Electron rays (2DEG)
AFM lithography (2DEG)
Resolution: ~40nm
Shuffling of atoms by tunnel microscope
Nobel Prize 1986.: E. Ruska; G. Binnig & H. Rohrer, electron microscope
- or sweeping tunnel microscope
„Leave it to Nature”
Self organizing structures
Coherent conducting phenomena
Quantifying conductivity
Aharonov-Bohm effect
The noise as sign
T is the transmission probability through a
point contact.
0<T<1 has noise
„The noise is the signal”
R. Landauer
The Quantum Hall effect
Klaus von Klitzing – Nobel Prize 1985.
fraction number Quantum Hall effect
H. Störmer, D.C. Tsui, R.B. Laughlin – Nobel Prize,
1998.
Composite fermions
Superconducting nanostructures , Andreev reflection
-Gauging Spin polarization by
Andreev spectroscopia
Phenomena of interference in diffusive NS contacts
Quantum dots
Charging energy
e2
 1meV  10 K
C
Atomic size molecular contact
examined by nanophysics
Caracteristis of conductivity in single-atom and molecular contacts
- Quantifying conductivity
- Fluctuating conductivity
- Shot noise
- Subgap structure
- Dinamic Coulomb blocade
- Spetroscopy of inelastic inductivity
Semiconductors
Basic semiconductors: Si, Ge
III-V Semiconductors: GaAs, AlAs, InAs,
InSb, GaSb, GaP, AlSb, InP
II-IV, IV-VI semiconductors
Applications in optics
(semiconductor laser, photodetector)
direct gap→→ indirect gap!
Band engineering
Band is continuously changed and mixed e.g. AlxGa1-xAs
GaAs, AlAs, AlxGa1-xAs
< 0.15% deviation
↓
In the lattice constant
Epitaxial growth is possible on
each other
Epitaxial growth 1.
MBE, Molecular Beam Epitaxy
Organised growth of atomic layers on each
other
Chambers to evaporate different
types of materials
Heated substrate; By diffusion the atoms
find their favourable lattice
high vacuum~ 10-10-10-11 mbar
Low growth: ~ 1 atomic layer/s
Epitaxial growth 2.
In situ analysis: e.g. RHEED
(Reflected High-Energy Electron Diffraction)
The intensity periodically oscillates in the
process of growth, so the atomic layers
can be controled.
The MBE is a perfect tool for growing heterostructures.
The composition, thickness and doping of the layers can be varied
arbitrarily
2DEG GaAs-AlGaAs in heterostructure
• n-AlGaAs GaAs
Remote doping - modulation doping
Doping in GaAs: Ga -> Si (n type donor)
Application:
High Electron Mobility Transistor
600GHz max fequency
The donor atoms have been removed from the
layer of electron gas
→
Exceptional mobility!
Formation of nanostructures /methods of growing
„Cleaved egde overgrowth”
1D quantum conduction
Formation of nanostructures /latexial structuring
Photolitography > 100nm)
Structuring
semiconducting layers
Forming gate eletrodes
Example: preparation of Hall
sample
Formation of nanostructures /lateral structuring
AFM litography
Contact of quantum dots
On the surface of semiconductors at room
temperature a thin water layer is formed by precise
control of vapour
Doped Si needle + high voltage->
Lines of oxides can be made on the surface
(width<100nm, height 20-30nm)
The 2DEG is removed on the oxide lines
quantum dot