Part 3 iii Scanning NearField Photolithography SNP Learning

Part 3 iii: Scanning Near-Field Photolithography (SNP)

Learning Objectives After completing PART 3 iii 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 m. M Hexane thiol solution SO 3 I Hr UV irradiation in air SH J. Am. Chem. Soc. 1993, 115, 5305

Static SIMS 10 Mins Photooxidation 40 Mins Photooxidation J. Am. Chem. Soc. 2001, 123, 4089 -4090

Patterning the C 60 Film SIMS Mask 254 nm Photooxidation

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 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/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 i. e. longer than the aperture l 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/nearfieldintro. html Strands of DNA http: //www. witec. de/pdf/alpha 300 Sflyer. pdf

Example of SNP 1

The SNOM as Lithography Tool Scanning Near Field Photolithograpgy

Scanning Near Field Photolithography, Oxidation and Back Filling 6 6 6 S N O M Au J. Am. Chem. Soc. , 2002, 124, 2414

AFM (Friction Force Mode) CH 3 CO 2 H 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 hm [O] hm DNA

(i) Convert acid into active ester (ii) Incubate with Calf Thymus DNA

Example of SNP 4

Writing to Gold Nanoparticles on Si. O 2 UV Radiation SO 3 S O 3 Aggregation of Gold S O 3 Nanoletters, 2006, 6, 345 S O 3

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 Solvent evaporates Si/Si. O 2 Spinning

Making 3 D Micron Scale Structures Parallel Exposure to 244 nm photons Irradiation/Rinsing 10 mm UV Masks 2 nm 40 nm Si/Si. O 2 70 nm Rinse Si/Si. O 2 Unirradiated rinse away particles

Proposal: Scanning Near Field Photolithography (SNP) 100 nm 2 nm 10 nm 40 nm Si/Si. O 2 x Si/Si. O 2 Rinse z y Si/Si. O 2

Proposal: Scanning Near Field Photolithography (SNP) 100 nm 2 nm 10 nm 40 nm Si/Si. O 2 This was a little disappointing as structures were greater than 100 nm 250 nm 120 nm x Si/Si. O 2 110 nm Rinse z y Si/Si. O 2 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 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 1 mm - 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 B 15 2 TT Department of Physics and Astronomy, University of Sheffield, S 3 7 RH School of Chemistry, University of Sheffield, Western Bank, Sheffield, S 10 2 TN

Reaction of C 60 Under UV Light Exposure • • Rao et al. demonstrated UV light exposure on C 60 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 C 60 film underwent photopolymerisation (2 + 2 cycloaddition) For Yr 2 and Yr 3 Chemists!! p 2 s + p 2 s 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 C 60 Langmuir-Blodgett Layer Structures 5 mm min-1 Air ~ 2. 5 nm Moveable Barrier Water

Patterning the C 60 Film Mask Substrate

Patterning the C 60 Film with SNP 0. 3 mm s-1 1 mm s-1 2 mm s-1 35 mm s-1

Conclusions on 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#