Transcript P202 Lecture 2

Building a more complex molecule
C2
Isolated impurities
From E. A. Moore: “Molecular Modelling and bonding”, Royal Soc. Chem.
Building a solid Graphite/Diamond
Isolated impurities
From W. A. Harrison: “Electron Structure” Royal Soc. Chem.
Building a metal (Copper)
Isolated impurities
From J. A. Burdick Phys. Rev. 129 138 (1963)
Building a Semiconductor
E
Isolated
atoms
Condensed
Phase
Conduction
Band
Available
States
No States
available
Valence
Band
Fill up the states with
electrons just like you fill
up atomic or molecular
states, fill from the lower
energy up being careful
to abide by Pauli.
The material properties
are dominated at by the
highest energy states that
are occupied.
1/R
Conduction band
Valence band
Localized states near
impurities;
These control
Isolated
impurities
the properties of the
semiconductor
Impurities in Semiconductors
•“Electrons” in solids can behave as if they have a different
mass and charge than free electrons. Why, the dynamics of
the material are really determined by the “excitations” of the
system (how it’s behaviour differs from the equilibrium
state).
•E.G. for Donors in Si you might expect E=(eo/e)2(m*/mo)EH
•For Si this works out to be about 25meV, and this is in
reasonable agreement with the experimental results for
shallow donors (even though we have left out a lot of
details that account for differences between elements like P
and As etc.
Band structure and Impurties
in Si and Ge
From S. SM .Sze “Physics of Semiconductor devices”, Wiley (1969))
Nano Technology/Materials
•Why interesting?
•Technological Applications (7 responses)
•How do we make things that small? (8 responses)
•Confinement energy becomes important (DVB)
•What would you like to hear more about?
•Quantum computing (7 responses)
•Applications in general (5 responses) life sciences (4)
•Buckyballs/Carbon Nanotubes (5 responses)
•How to make them? (4 responses)
Key Properties of Materials
• Electrical Conductivity
• Hall Effect (balance of Lorentz and Electric forces within
a wire carrying a current in a magnetic field).
– Useful for measuring carrier concentration and type
(electrons vs. holes)
– Ubiquitous for measuring magnetic fields
• Thermo-electric Effects
– Electrons carry both charge and energy, hence the
two can be coupled.
– Used widely for measuring temperature
• Piezoelectric effects (strain<-> voltages)
– Used in SPM’s, small sensors etc.
Lecture 32
Semiconductor Laser
http://www.explainthatstuff.com/laserdiode.png
The Field-Effect Transistor
Inside an Integrated Circuit
From Mayer and Lau (1990)
Materials Science:
Interdiffusion, anisotropic etching,
electromigration, diff. therm. exp.
From T. N. Thies IBMJRD (2000)
Condensed-matter Physics:
Quantum Hall effects, quantum
interference, non-local transport
Integer Quantum Hall Effect
1985 Nobel Prize
Von Klitzing
Fractional QHE
A very rich area of
CMP for 2 decades,
Anyons, Skyrmions,
Coulomb drag …
1998 Nobel Prize
Laughlin, Tsui, Stormer
Fractional QHE
A very rich area of
CMP for 2 decades,
Anyons, Skyrmions,
Coulomb drag …
1998 Nobel Prize
Laughlin, Tsui, Stormer
Take-home lesson:
It’s the excitations
(stupid!); the low-lying
Excitations of a manyParticle system determine
Its properties!
The Field-Effect Transistor
Photo-lithography
(the birth of nano-tech)
http://www.hitequest.com/Kiss/VLSI.htm
Inside an Integrated Circuit
From Mayer and Lau (1990)
Materials Science:
Interdiffusion, anisotropic etching,
electromigration, diff. therm. exp.
From T. N. Thies IBMJRD (2000)
Condensed-matter Physics:
Quantum Hall effects, quantum
interference, non-local transport
Fractional QHE
A very rich area of
CMP for 2 decades,
Anyons, Skyrmions,
Coulomb drag …
1998 Nobel Prize
Laughlin, Tsui, Stormer
Take-home lesson:
It’s the excitations
(stupid!); the low-lying
Excitations of a manyParticle system determine
Its properties!
ENIAC
1946
• Electronic Numerical Integrator And Computer
• 17468 vacuum tubes
• weight 20 t, power consumption 150 kW
Vorlesung Quantum
Computing SS ‘08
20
Moore’s law
http://www.intel.com/technology/mooreslaw/
Vorlesung Quantum
Computing SS ‘08
21
??e
:
quantum effects in silicon
technology barrier silicon
year
source:
Vorlesung Quantum
Computing SS ‘08
proteins, macro-molecules
minimum size of chip components (nm)
semiconductor industry
exponential extrapolation
size of viruses and DNA
breaking the barrier?
We may be starting to see
this flatten out, latest Intel
processors are using a “32
nm” process, and they are
planning for 22nm. Previous
generations had used a
“45nm” process.
http://techreport.com/articles.x/18216
Gold Nano-particles
Color varies with particle size (red stained glass
From the middle ages uses gold nano-particles)
http://www.meliorum.com/gold.htm?gclid=CObsuZfvlJ4CFQOdnAodoEl-qA
Gold Nano-particles
Color varies with particle size (red stained glass
From the middle ages uses gold nano-particles)
http://www.nsec.ohio-state.edu/teacher_workshop/Gold_Nanoparticles.pdf
For even more exciting applications see the Dragnea group site in IU Chem.:
http://www.indiana.edu/~bdlab/research.html
Self-Assembly routes to
nanomaterials
Nanostructures from
Self-Assembly
http://cae2k.com/photos-of-aloha-0/mcm-41.html
http://igitur-archive.library.uu.nl/dissertations/2003-0325-143241/inhoud.htm
This self-assembly can be used to make materials with
molecular size control (e.g. MCM-41 and related silicates)
Discovery of the Neutron
T&R Figure 12.1
Chadwick (1932, building on earlier
work by Both and Becker, and later
I. Curie, and Joliot) demonstrated
that the unknown radiation must
have a mass of the same order as
the proton by measuring the energy
of recoil nuclei of various mass.
Size of Nuclei
T&R Figure 12.2
R = ro A1/3
Trends in Nuclear Stability
See also: T&R Fig. 12.6
Please note two things from
this figure:
1. The binding energy per
nucleon peaks at 56Fe
(CALM)
2. Note the peaks at 4He
16O, and (to some extent)
at 12C.
http://www.tutorvista.com/physics/binding-energy-per-nucleon
2
10
18
36
54
86
Closing a shell->
Stable atom,
high ionization
energy
http://www.corrosionsource.com/handbook/periodic/periodic_table.gif
Magic numbers in Nuclei
Note the sharp
(protons)
drop in
separation
energy at
atomic numbers
of 9, 21, 29,51,
and 83
From E. Segre “Nuclei and Particles
Magic numbers in Nuclei
(neutrons)
From E. Segre “Nuclei and Particles
Shell model for Nuclei
From E. Segre
“Nuclei and Particles”
3-D Harmonic
Oscillator
Spherical
Square well
Trends in Nuclear Stability
T&R Figure 12.5
See also Nudat2 at:
http://www.nndc.bnl.gov/nudat2/
Types of Radiation
http://www.nndc.bnl.gov/nudat2/reColor.jsp?newColor=dm
Types of Radiation
•Alpha (a):
•4He nucleus; very easy to stop (paper,etc.)
•Beta (b)
•Electrons or positions, relatively easy to stop
•NOTE: you can also get high-energy electrons through
“internal conversion” and the Auger process, but strictly
speaking, these do not come from beta decay, and are
therefore not, technically, “beta” particles (even though they
behave exactly the same way).
•Gamma (g)
•High-energy photons (of nuclear origin)
•X-rays
•High-energy photons (of atomic origin)
•Neutron (n)
•Protons, ions
Types of Nuclear Decay
•Alpha (a):
•4He nucleus;
•Beta (b)
•Electrons or positions, of nuclear origin
•Electron Capture
•Gamma (g)
•(gamma, internal conversion do not change nucleons).
•Spontaneous fission
•proton
•Neutron (n)
http://library.thinkquest.org/3471/radiation_types.html
Examples
• What is the binding energy per nucleon of
56Fe?
• The mass of 12553I is 124.904624u and that
of 12552Te is 124.904425 u. What decay
mode is possible between these two
nuclei?