Transcript Slide 1

Part 3iii:
Scanning Near-Field
Photolithography
(SNP)
Learning Objectives
After completing PART 3iii of this course you should have an understanding of, and be
able to demonstrate, the following terms, ideas and methods.
(i)
The photo-oxidation process of thiolates to sulfonates on gold,
(ii)
Appreciate how the surface chemistry is probed by various spectroscopic
techniques,
(iii) Appreciate how the modified surfaces can be utilised as platforms for
building the structures into the third dimension,
(iv) Appreciate the various chemistries that are initiated by the radiation,
(v)
Appreciate how an AFM operates,
(vi) Appreciate how a SNOM operates, and
(vii) Appreciate how SNP works
Background
Some Surface Photo-oxidation
Chemistry
Photoxidation of Thiol SAMs on Golds and Silver
XPS
Immersion for 1 Hr in 1 mM
Hexane thiol solution
SO 3
I Hr UV irradiation in air
SH
J. Am. Chem. Soc. 1993, 115, 5305
HO
Static SIMS
O
10 Mins
Photooxidation
S
40 Mins
Photooxidation
Ag
S
Ag
O 3S
J. Am. Chem. Soc. 2001, 123, 4089-4090
Patterning the C60 Film
SIMS
HO
O
Mask
HS
254 nm
Photooxidation
HO
O
HS
O3S
Background
An Atomic Force Microscope
(AFM)
The Atomic Force Microscope Set-Up
A key element of the AFM is its force sensor, or cantilever. The cantilever is usually formed by
one or more beams of silicon or silicon nitride that is 100 to 500 microns long and about 0.5 to 5
microns thick. Mounted on the end of the cantilever is a sharp tip that is used to sense a force
between the sample and tip. For normal topographic imaging, the probe tip is brought into
continuous or intermittent contact with the sample and scanned over the surface. Fine-motion
piezoelectric scanners generate the precision motion needed to generate topographic images
and force measurements. A piezoelectric scanner is a device that moves by a sub-nanomtere
amounts when a voltage is applied across its electrodes. Depending on the AFM design,
scanners are used to translate either the sample under the cantilever or the cantilever over the
sample.
Piezoelectric scanners for AFMs usually can
translate in three directions (x, y, and z axes) and
come in different sizes to allow maximum scan
ranges of 0.5 to 125 microns in the x and y axes
and several microns in the vertical (z) axis. A
well-built scanner can generate stable motion on
a scale below 1 Angstrom.
By scanning the AFM cantilever over a sample
surface (or scanning a sample under the
cantilever) and recording the deflection of the
cantilever, the local height of the sample is
measured.
Three-dimensional
topographical
maps of the surface are then constructed by
plotting the local sample height versus horizontal
probe tip position
The AFM Cantilever and Tip
The Tip is an Atom!!
Tip
Atomic Resolution
Background
Scanning Near Field Optical
Microscope
(SNOM)
SNOM/NSOM
http://www.olympusmicro.com/primer/techniques/nearfield/nearfieldhome.html
Drawn or etched fibre optic cable
appended to AFM cantilever
Or hole made in the end of an AFM tip
Wavelength of light 180-300 nm
l
i.e. longer than the aperture
Therefore diffraction…
Which is limited by being used in the near field
Aperture
~50 nm
~10 nm
SNOM/NSOM
http://www.olympusmicro.com/primer/techniques/nearfield/nearfieldintro.html
Strands of DNA
http://www.witec.de/pdf/alpha300Sflyer.pdf
Example of SNP 1
The SNOM as Lithography Tool
Scanning Near Field Photolithograpgy
Scanning Near Field Photolithography,
Oxidation and Back Filling
CO2H
6
SH
6
S
N
O
M
SO3
6
SH
Au
J. Am. Chem. Soc., 2002, 124, 2414
AFM (Friction Force Mode)
CH3
CO2H
Lines
6 x 6 mm
J. Am. Chem. Soc., 2002, 124, 2414
Example of SNP 2
Scanning Near Field Photolithography,
Oxidation and Etching
Fe(CN)62+/Fe(CN)63+ (aq)
30 mins
11
SH
11
S
N
O
M
SO 3
Au
Nanoletters, 2002, 11, 1223
Example of SNP 4
Chemical Modifying the SAM Surface Group
NANO LETTERS, 2006, 6, 29-33
O
Cl
hm
Si
O
hm
[O]
Si
Si
O
OH
OH
DNA
Si
Si
O
OH
Si
(i) Convert acid
into active ester
(ii) Incubate with
Calf Thymus DNA
O
OH
Si
Example of SNP 4
Writing to Gold Nanoparticles on SiO2
S
S
S
S
S
UV Radiation
S
S
S
S
SO
S
3 SO
3
S O3
S O3
S O3
Aggregation of Gold
S O3
Nanoletters, 2006, 6, 345
S O3
S O3 S O
3
S O3
Making a Thin Film of Nanoparticles:
Spin Coating
Decane thiol passivated
nanoparticles (1-3 nm)
gold
M. Brust, M. Walker, D. Bethell, D. J.
Schiffrin, R. Whyman, J. Chem. Soc.,
Chem. Commun., 1994, 801-802.
Volatile
solvent
S
S
Solvent
evaporates
S
S
S
S
S
S
S
S
S
S
S
S
S
S
Si/SiO2
Spinning
Making 3D Micron
Scale Structures
Parallel Exposure to 244 nm photons
Irradiation/Rinsing
10mm
UV Masks
2nm
40nm
Si/SiO2
Si/SiO2
70 nm
Rinse
Si/SiO2
Unirradiated
rinse away
particles
Proposal: Scanning
Near
Field
Photolithography
(SNP)
100 nm
2 nm
10 nm
40 nm
Si/SiO2
x
Si/SiO2
Rinse
z
y
Si/SiO2
Proposal: Scanning
Near
Field
Photolithography
(SNP)
100 nm
2 nm
10 nm
40 nm
Si/SiO2
This was a little
disappointing as
structures were
greater than 100 nm
250 nm
120 nm
x
Si/SiO2
110 nm
Rinse
z
y
Si/SiO2
14 nm
Solution? Making a Thinner Film of the Gold Nanoparticles
Langmuir-Schaeffer Layer Structures
Repeat to obtain a bilayer
Air
Moveable
Barrier
Water
Langmuir-Schaeffer Bilayers and SNP Structures
60 nm
60 nm structures indicates that the
excitation does not spread outside
the area illuminated by the probe, in
contrast to the behavior observed for
the spin-cast films.
The structures are continuous and
appear generally free from defects,
with some thinning.
~ SNOM Aperture
6 nm High
~2 x diameter of the particles
Making Carbon
Nanowires with
Photons:
Scanning Near Field
Photolithography
1mm
-
ee
+
Writing Wires
Parvez Iqbal†, Marcus D Hanswell‡, Shuqing Sun,# Tim Richardson‡, G. Leggett#
and Jon A. Preece†
†School
‡
of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT
Department of Physics and Astronomy, University of Sheffield, S3 7RH
School of Chemistry, University of Sheffield,Western Bank, Sheffield, S10 2TN
Reaction of C60 Under UV Light Exposure
•
•
Rao et al. demonstrated UV light exposure on C60 film led to a insoluble
material in toluene
Through Raman and infrared spectroscopy, x-ray diffraction and Laser
desorption mass spectroscopy concluded that the exposed C60 film
underwent photopolymerisation (2 + 2  cycloaddition)
For Yr2 and Yr3 Chemists!!
2s + 2s
Photochemical
Cycloaddition
~ 1 nm
UV light
LUMO (ene)
SOMO (ene)
Combination
M. Rao, P. Zhou, K.-A. Wang, G. T. Hagar, J. M. Holden, Y. Wang, W.-T. Lee, X.-X. Bi, P. C. Eklund,
D. S. Cornett, . M. A. Duncan, I. J. Amster, Science, 1993, 259, 955
Making a Thin Film of C60
Langmuir-Blodgett Layer Structures
5 mm min-1
O
O
O
Air
O
~ 2.5 nm
O
O
O
O
Moveable
Barrier
O
O
OH
HO
Water
Patterning the C60 Film
Mask
Substrate
Patterning the C60 Film with SNP
0.3 mm s-1
1 mm s-1
2 mm s-1
300
Line width (nm)
250
200
150
100
50
35 mm s-1
0
0
0.5
1
1.5
Writing speed (mms-1)
2
2.5
Conclusions on SNP
SNP is a very facile and versatile route to create nanostructured surfaces, with
resolution better than photolithography and almost equalling EBL.
It requires relatively cheap instrumentation and is carried out under ambient
conditions.
Only the tip of the iceberg has been looked at to date as to what type of SAMs and
functional groups might be modified, and there is a whole host of chemical reactions
that have been studied in the solution phase that could be transferred to the surface.
Major disadvantage of SNP (and EBL) is that it is a serial process and therefore
slow, unlike photolithography.
Summing Up Part 3
Photolithography is a rapid parallel process, but is struggling with to keep pace
with Moore’s law.
E-beam lithography is a slow serial process, but can create nanoscale structures.
However, it requires the use of expensive intrumentation and UHV conditions.
SNP is a slow serial process, but can also create nanoscale structures. In
addition, it is a relative cheap and facile methodology, being carried out under
ambient conditions.
MAPPER
An array of around 14,000 direct write electron beams
Millipede
An Array of AFM cantilvers and tips
http://www.zurich.ibm.com/st/storage/concept.html#