国际会议海报Poster模板

1、Scanning near-field optical lithography (SNOL) of organic semiconductors Dan Credgington1, Oliver Fenwick1, Ana Charas2, Jorge Morgado2, Klaus Suhling3and Franco Cacialli1 1 UCL Department of Physics and Astronomy and London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, UK. 2 Inst

2、ituto de Telecomunicaes, Instituto Superior Tcnico, Av. Rovisco Pais 1, P-1049-001 Lisboa, Portugal. 3 Department of Physics, Kings College London, The Strand, London WC2R 2LS, UK. Scanning near-field optical lithography (SNOL) has been shown to provide a versatile method for patterning materials ov

3、er lengths well below the classical diffraction limit.We apply this technique thin films of organic semiconductors. These optically and electronically active materials are chemically tuneable, flexible, and can often be processed directly from solution. For applications in photonic devices and nano-

4、electronics, achieving lithographic resolution on the nano-scale is vital.Using a home-built SNOL system, we demonstrate how thin films of the widely studied polymer poly(para-phenylene-vinylene) (PPV), and the cross-linkable oxetane derivatives F8Ox and BTOx can be patterned to any predetermined de

5、sign. The SNOL probe: a sharpened, metal-coated optical fibre with a sub-wavelength aperture defined at the apex 325nm HeCd laser launched into the fibre. Opticalnear-fieldgeneratedaroundthe aperture Contact is maintained using shear-force feedback IN SUMMARY, scanning near-field optical lithography

6、 is a powerful tool for patterning materials on the nano-scale. We have investigated the resolution achievable with our system, as applied to the patterning of PPV, and found that a feature size of around 50nm are possible. We have also shown that, in addition to individual small structures, creatin

7、g large arrays and more complicated designs is equally feasible using SNOL. Finally, we have shown that a variety of other materials are suitable for patterning via this technique, including BTOx and F8Ox, which undergo a very different reaction to PPV. -5 0 5 10 0100200300400 nm nm -5 0 5 10 nm 60n

8、m75nm A B 200nm B A 10m 1m(Left)AFMscanofa features drawn in PPV on a varietyoflengthscales, froma15nmthick precursor film using a 50nm near-field probe. 5m X BTOx r-BTOx UV activation -50 0 50 1 00 1 50 200 01234567891 01 1m nm X 500nm Photoinitiator Cross-linking through oxetane side- chainsactiva

9、tedviaaphotoacid initiator. Cross-linked reticulated network (r- BTOx) forms. Development in THF removes the unexposed polymer. Sub-wavelength aperture Incident laser Log (Intensity) Thin film (Right) 3-dimensional representation of the optical field strength in a thin film placed below the tip of a

10、n apertured SNOL probe. Optical intensity distribution is calculated with the Bethe-Bouwkamp model ( = 325nm, aperture diameter 50nm, film thickness 20nm and film refractive index 1.73 + 0.067i.) PPV BTOx SNOL Optical fibre probe Quartz tuning fork Sample Contacts Probe tip x z y Acopolymerbasedarou

11、ndthe commongreen-emittingpolymer F8BT. (Right, bottom) cross section through the pillars, typical feature size of around 500nm. PPVstructuresfabricatedviaa Wessling-type precursor process using SNOLtoconvertpoly(p-xylene tetrahydrothiophenium chloride) (PXT) in-situ into conjugated PPV. Unexposed P

12、XT removed using methanol PXT UV activation PPV (Right, top) An array of pillars defined in r-BTOx from a 200nm film using a 60nm probe aperture Unbaked Height (nm) 01020304050 Baked Height (nm) 0 10 20 30 40 Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Unbaked FWHM (nm) 0100200300400 Baked FWHM (nm

13、) 0 100 200 300 Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 (Below)Cross-sectionsof the finest features. 5m 200nm X 0 2 4 6 8 1 0 0501 001 50200 nm nm X 55nm (Left) Dots drawn in PPV from a 15nm film, using a 50nm probe aperture. (Right) Zoomandcross-sectionthroughthis feature showing FWHM of appro

14、ximately 55nm. 10050200500 1000 Exposure time (ms) Structure of 65,000 pixels. Minimum resolution 60 nm. Integrity of aperture maintained. Non-uniform shrinkage during baking Uniform films shrink 50% during baking. Height and width of nano-sized dots measured before and after baking Linear fits to d

15、ata give :nmWW ubb 46 nmHH ubb 37 . 0 W = width (FWHM) H = height b = baked ub = unbaked 30% vertical shrinkage Outer layers collapse a fixed 20-25 nm around the edge (not dependent on lateral dimension) Poly2,7-(9,9-dioctylfluorene-alt-benzothiadiazole)-co-1,4-(2,5-bis-(methyl-4-(6-(3-methyloxetan-

16、3-yl)methoxy)hexyloxy)benzene) F8Ox Oxetanesidechains(analogueto BTOx). Blue-emitting. Photoluminescence preserved during lithography. Under-exposureresultsinpoorly positioned features (area C). (Left) Arrays of pillars defined in r-F8Ox from a 200 nm film using a 60 nm probe aperture. Exposure decr

17、eases from A (200 ms) to B (50 ms) to C (20 ms). (Right) Confocal photoluminescence images of the same areas. We thank: the EPSRC; the RS; the EC for funding of the RTN THREADMILL (EU-contract: MRTN-CT-2006-036040); the European Science Foundation EUROCORES Programme SONS with supplementary funds from EPSRC and the EC Sixth Framework Programme (ERAS-CT-2003-980409); as well as the EC Seventh Framework Programme (FP7/2007- 2013) under grant agreement N. 212311 (ONE-P).