How do we see nanostructures?

Figure 1.3.2 Electron micrograph of an SiO

/Si interface in a

transistor.

Fig. 1.3.1 Cartoon of the action of a quantum well laser.

Parallel Spin Filters

→

Resistance Low

Opposing Spin Filters

→

Resistance High

Giant Magnetoresistance (GMR)

Figure 1.3.3 GMR (giant magnetoresistive) spin valve reading head. At the upper left is a diagram showing how the GMR
phenomenon is used to control current. At the upper right, a graph of signal versus sensing layer thickness shows the optimum
thickness. At the bottom is a diagram showing the interaction of the read/write head and the magnetic storage medium. The GMR
read head is the red block with the read current passing through.

Figure 1.1.2 shows diagrammatically just how much storage density can still be increased. Today's commercial
media can store about 14 Gbits/inch

. To achieve this density, the storage medium required to store one bit is a

rectangle of dimensions 600 nm by 50 nm. This is represented by the blue rectangle in the middle of Figure 1.1.2.
Think of the neighboring rectangles as bits that are magnetically oriented in the other direction. One can see how
many 10nm particles are covered by each of the bits, and how much storage density would increase if one can
use one particle to store one biteven without shrinking the size of the particles themselves.
For a good synopsis on how far storage density has already advanced, visit IBM's

disk storage system

page.

Figure 1.1.2 Cartoon showing how much room on a magnetic storage medium is currently needed to store one
bit.

• A photolithography system

consist of a projection

system, a mask, and a

surface coated with a

photo-sensitive film

• The light changes the

properties of the film

locally

• This allows the film to be

partly removed and the

substrate to be selectively

exposed to etching or

deposition

Photo lithography

Top: STM image of a

quantum corral

consisting of a ring of iron

atoms assembled on a copper surface. It can be used to

mainpulate the electron wave function. The waves inside the ring
represent direct detection of the electron wave function by STM;
there is no iron atom in the center

•

Quick Facts About Carbon Nanotubes

•

Equilibrium Structure

•Average Diameter of SWNT's 1.21.4 nm
•Distance from opposite Carbon Atoms (Line 1) 2.83 Å
•Analogous Carbon Atom Separation (Line 2) 2.456 Å
•Parallel Carbon Bond Separation (Line 3) 2.45 Å
•Carbon Bond Length (Line 4) 1.42 Å
•CC Tight Bonding Overlap Energy ~ 2.5 eV
•Group Symmetry (10, 10) C5V
•Lattice: Bundles of Ropes of Nanotubes: Triangular
Lattice(2D)
•Lattice Constant 17 Å
•Lattice Parameter:
•(10, 10) Armchair 16.78 Å
•(17, 0) Zigzag 16.52 Å
•(12, 6) Chiral 16.52Å
•Density:
•(10, 10) Armchair 1.33 g/cm3
•(17, 0) Zigzag 1.34 g/cm3
•(12, 6) Chiral 1.40 g/cm3
•Interlayer Spacing:
•(n, n) Armchair 3.38 Å
•(n, 0) Zigzag 3.41 Å
•(2n, n) Chiral 3.39 Å