纳米技术-课件04

3. Polymerization, formation of a stamp.
6. Molecules are transferred !!
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4.1.8 Lift-off techniques
Experimental sequence of the conventional lift-off
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4.1.3 e -beam lithography
Example:
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4.1.4 Comparison of lithography techniques
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Example: AFM induced nano-oxidation
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4.1.7 Soft lithography
General experimental sequence of soft lithographu
1. Preparation of the stamp
k = 0.5-1 NA=sin α ? 1 (numeric aperture)
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4.1.1 Photolithography technique
Projection and stepper
α
Resolution Numeric aperture
NA=sin α
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4.1.1 Photolithography technique
Lithographic printing modes & resolution limitation - Direct contact: R ~ λ - Proximity: R ~ (λ d)1/2 - Projection: R = k (λ/NA),
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4.1 Nano-scaled lithography (top-down)
Photo-lithography a X-ray lithography
Lithography using scanning probe instruments - Electron-beam lithography (based on SEM) - Dip Pen Nanolithography (based on AFM) Soft-lithography techniques Lift-off techniques:
4.1.5 Dip pen nano-lithography
Equipment availability: SEM
water
The wiggly lines are molecular “ink”
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4.1.6 Dip pen nano-lithography
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4.2 Nano-manipulating
2: Examples: Manipulating atoms using STM
Single atom removal
IBM advertisement made of Xenon atoms
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4.3.1 Physical vapor deposition (PVD)
Generate atomic/molecular fluxes by a physical process
Thermal evaporation Sputtering deposition
4.3 Nano-scale crystal growth (bottom-up)
Growth techniques Physical vapor deposition (PVD) - Molecular beam epitaxy (MBE) Chemical vapor deposition (CVD) - Atomic layer epotaxy Growth from the liquid phase
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4.1.2 X-ray lithography
Mask fabrication
Normal mask
Quartz sub + Cr
X-ray mask
Si frame + Si3N4 membrane + Cr
Synchrotron X-ray source
Self-ordered growth of the patterned substrates
Shadow growth
Cleave edge over growth of a multi layer sample
Growth on V-grooves
Templating against step edge
+ Direct writing (focused beam + scanning)
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Difficulty for large quantity production
Physical limitation: electron scattering (replacement: ion-beam lithography(?), but ion-beam damage)
+ Can use simple proximity print mode for largequantity production + Availability of masks and resists Disadvantages _ Very expensive light source, e.g. using synchrotron radiation
STM tip evaporating the atom Pick-up the atom Large E field between the tip and substrate E field stimulated evaporation of the surface atom Capturing an atom using the tip Move the atom to other places Using the attractive force Move the atom
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4.3.4 Molecular beam epitaxy (MBE)
MBE equipment at IFM/LiU
VG V-80
Balzers UMS-630
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4.3.5 Growth of 1-D nano-wires substrates
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4.3.6 Growth of semiconductor nano-whiskers
target Sputtered atoms
e-gun
Ar+ ions
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4.3.2 Surface processes
When atoms/molecules arrive on the surface
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4.3.3 Growth modes
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4.1.1 Photolithography technique
Photo-lithography
Basics components: light source, mask, aligner, resist - Light source g-line (Hg-Xe): 436 nm i-line (Hg-Xe): 365 nm KrF: 248 nm ArF : 193 nm F2: 157 nm - Positive & negative resist
1. Produce patterns on the Si sub. 4. Incubate molecules on the stamp
2. Pull PDMS on the patterned Si sub.
5. Stamp molecules on the Au-coated sub.
Pattern revealing by the surface wetting test
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4.1.3 e -beam lithography
Equipment availability: SEM Short equivalent wavelength a High resolution λe = h/(2meE)1/2; 1eV ? 12.3 Å.
Nano-CAD (computer-aided-design)
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Vision
To integrate the ”top-down” approach with the ”bottom-up” approach
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2. Transfer patterns or ng
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4.1.7 Soft lithography
Example: molecule transfers