PH454 nanoscience

What is a 2D structure?

particle free movement in 2 directions, quantization of particle motion in 1 direction

What is a 1D structure?

free movement in 1 direction, quantization in 2 directions

What is a 0D structure?

no free movement, quantized in 3 directions

what are the assumptions in the free electron model?

electrons have constant potential and interactions are ignored

What is the fermi energy?

energy of highest occupied energy level

what does the density of state function do?

describes the number of states that are available for a system

what are the degrees of confinement for 3d,2d,1d & 0d

0,1,2,3

what is dN/dE for 3d,2d,1d & 0d

3d = sqrt(E), 2d = 1, 1d = 1/sqrt(E), 0d = delta(E)

for a coulomb blockade, is the charging energy (e^e/2C) larger than thermal energy (kT) for small systems?

yes

what makes a coloumb blockage easier to see?

low temperatures

can large islands do coulomb blockages?

no, only small since it depends on C

what happens when an electron overcomes that charging energy in a coulomb blockage?

it tunnels

name 2 approaches on nanofabrication

top-down and bottom-up

what is physisorption?

weak interaction, molecules retains its gas phase structure

what is chemisorption?

chemical bonding of adsorbed substances (irreversible)

do all atoms absorb if they find a site to land on?

no, only a fraction will

what is Volmer-Weber (VW) growth

three-dimensional adatom clusters or islands on a substrate

What is Frank-Van der Merve (FM) growth?

atomically smooth, fully formed 2d layers

What is Stranski-Krastanov growth?

both smooth 2d layers and 3d cluster/islands

What is coalscence in thin film growth?

islands forming a network by touching each other, temperature dependent

What is shadowing in thin films?

incoming admolecules at angles, dominant at low temps

What is surface diffusion in thin films?

mobility of admolecules at surfaces and grain boundaries, dominant at medium temps

what is bulk diffusion in thin films?

mobility of admolecules in the volume of grains, dominant at high temps

what is recrystalisation in thin films?

phase transition as a change of crystal orientation

What does physical vapor deposition (PVD) involve?

generation of vapor phase species via evaporation, sputtering or laser ablation

what set up is this for?

PVD evaporation processes that utilize heat and vacuum to deposit thin films.

which one is chemisorption?

3, also known as chemical bond formation

which one is adsorption (physisorption)?

1

which one is surface diffusion?

2

which one is bulk nucleation?

4

in oblique angle deposition (OAD) what growth is used?

shadowing effects

low mobility, limited surface diffusion and low temperatures are needed for what type of deposition?

oblique angle deposition

what deposition technique is this?

ion-beam assisted deposition, technique that combines ion implantation with other PVD technique.

advantages of chemical vapour deposition?

simple apparatus, high deposition rate, very uniform, high density

what type of deposition is this?

atomic layer deposition (ALD)

what technique uses this apparatus and epitaxial growth?

molecular beam epitaxy (MBE)

what does nanolithography mean?

fabrication of patterns with 1 dimension being under 100nm

how does photolithography work?

remove parts of a thin film/bulk of substrate using light and a mask

these steps are for what type of lithography?

photolithography

what does a positive resist do?

soluable in the photoresist developer

what does a negative resist do?

insoluble in the photoresist developer

how does x-ray lithography work?

uses x-rays to transfer geometer patterns using masks

which lithography technique overcomes the diffraction limit of light?

electron-beam lithography

name the lithography technique being used

electron-beam lithography

what lithography techniques dont need a mask?

ion-projects, electron beam, FIB, proton-beam

what lithography technique uses jet printing?

digital lithography

name the lithography technique

nano-imprint lithography (NIL)

what does dip-pen lithography involve?

AFM (atomic force microscopy) tip coated with thin film of ink molecules that interact

what is scanning probe lithography?

includes STM and AFM

what do focused ion beam techniques (FIB) use in the beam

slow and heavy ions

What type of particle do proton beam techniques use?

fast protons

what type of deposition is this?

gas assisted selective depositionS

fill in the blank: this is gas assisted _____?

etching