Topic Name: 3D multi-photon lithography

Category: Nanofabrication

Research persons: Prof. Joseph Perry,Vincent Chen,

Location: Chemistry & Biochemistry,Georgia Institute of Technology,901 Atlantic Drive,Atlanta, GA 30332-0400, United States

Details

Producing three-dimensional polymer line structures as small as 65 nanometers wide just became easier with new two-photon absorbing molecules that are sensitive to laser light at short wavelengths, allowing researchers to create them without highly sophisticated fabrication methods.
Fabricating such small features normally requires expensive electron beam or extreme ultraviolet lithography equipment. However, using a technique called 3D multi-photon lithography simplifies the process and reduces the cost. The technique could compete with existing processes for fabricating nanoscale electronic, photonic and microfluidic devices.
“Being able to obtain line widths down to 65 nanometers, which is substantially below prior published work of 100 nanometers, opens up new applications for multi-photon lithography,” said Joseph Perry, a professor in the Georgia Tech School of Chemistry and Biochemistry and the Center for Organic Photonics and Electronics.
The technique scans a laser beam across a substrate coated with a polymer resin containing a unique dye to create a desired hardened polymer structure. The laser writing process takes advantage of the fact that the chemical reaction of cross-linking occurs only where molecules have absorbed two photons of light. Since the rate of two-photon absorption drops off rapidly with distance from the laser’s focal point, only molecules at the focal point receive enough light to absorb two photons.
The fabrication method and dye were described in the March 19 issue of Optics Express. The research was supported by the Office of Naval Research APEX Consortium and the National Science Foundation, through the Science and Technology Center for Materials and Devices for Information Technology Research.
Seth Marder and Stephen Barlow, also researchers in the School of Chemistry and Biochemistry and the Center for Organic Photonics and Electronics, synthesized the unique molecule called DAPB, 4,4’-bis(di-n-butylamino)biphenyl, to initiate the chemical reaction leading to the hardening of the polymers when exposed to laser light.
“We needed a dye with good two-photon absorption at a wavelength of 520 nanometers, so we tried DAPB,” explained Perry. “DAPB proved to be very effective in this kind of lithography.”
The molecule developed by Marder and Barlow is about ten times more efficient at absorbing light by two photon absorption than commercial ultraviolet photoactive materials. That efficiency allowed Perry and graduate students Wojciech Haske and Vincent Chen, research scientist Joel Hales and postdoctoral associate Wenting Dong to create 3D patterns with nanoscale lines at light intensities low enough to avoid damaging the polymers.
For the experiments, a film of the polymer resin containing DAPB was formed. When the film was exposed to the focused laser, DAPB was excited and triggered cross-linking, leaving the insoluble scanned structure on the surface of a substrate when placed in a developer solution.
Since Perry controls where the Ti: Sapphire pulsed laser scans with a computer program, the polymers can be cross-linked in any pattern including 3D stacks of straight lines that are connected and sturdy. The laser beam is turned on to expose lines of polymer and off when no line should be drawn.
Conventional lithography involves creating a specific pattern on a mask for each new layer and exposing each layer to light and developing it. With this new technique, three-dimensional layered nanostructures can be created simply by having a computer program scan a different pattern for each layer. Mask templates become unnecessary and the coating, exposing and developing processes only have to be conducted once.
“We can create essentially any pattern we want. For this work, some of the patterns look like walls or lines suspended across walls and some are like a tall stack of crisscrossed lines,” noted Perry.
Perry and Marder co-founded a company in 2003 called Focal Point Microsystems that is working to commercialize this fabrication technology.
“We can write very small lines and create stacked-up grids of lines called photonic crystals,” explained Perry. “This work shows that we can fabricate functional photonic micro-devices with tailored transmission capabilities.”
It takes only 10 minutes to create a 20 micron by 20 micron structure with 30 layers, Perry added. Perry envisions using this technology to create compact micro-spectrometers on a chip for use in telecommunications and sensors. It may also be used as a compact way to separate the multiple wavelengths traveling through a fiber optic cable.
This type of simple, table-top technology may also be useful to fabricate customized types of circuits with many layers, which would be extremely expensive with standard methods because each layer would require a special mask.
“With the combination of the right molecule and short wavelength light, we’ve demonstrated that we can obtain nanoscale features. We’re at 65 nanometers now and we’re still trying to go smaller,” said Perry.

About researcher:

Joseph Perry

Professor

Office: MSE G209B

Phone: 404-385-6046

Fax: 404-894-7452

E-mail Joseph Perry

B.S., University of South Florida, 1977 ; Ph.D., California Institute of Technology, 1984

Research Interests

Physical, Polymer and Materials Chemistry; Optical Science. Our research program focuses on understanding how the chemical structures of molecules and materials relate to their electronic and optical properties. We employ a molecular approach in which fundamental structure-property relations are defined through a coordinated synthesis, theory and characterization program. In particular, we seek to develop a fundamental understanding of how to control the interactions of light and matter, and use this understanding to design and synthesize molecules and material for applications in photonics, materials processing, biology, and medicine. We collaborate with theoretical, physical, and analytical chemists, optical scientists, and biologists providing researchers a multidisciplinary training.
 

major focus of our research involves nonlinear optical absorption, wherein a molecule absorbs two or more photons at once. This process is intensity dependent; for two-photon absorption (TPA) the absorption rate increases quadratically with intensity. This allows activation of photo-chemical or photo-physical processes with high spatial resolution in 3-D. Current and future research directions are as follows: 1) In collaboration with Professor Marder's group, we are investigating structure-property relationships for TPA in conjugated molecules, with the goal of learning how to design efficient two-photon absorbers. These studies involve measurements of TPA spectra on molecules with systematically varied structures with dipolar, quadrupolar or octupolar charge redistribution. Excited-state Raman spectroscopy will be used to investigate the influence of excited-state structure and delocalization on TPA. 2) We are investigating excited-state reactions of systems excited by TPA. Current work focuses on molecules that undergo excited-state charge-transfer reactions following TPA and can thereby initiate polymerization. 3) TPA driven chemistry is being investigated for the 3-D patterning of materials. Using a femtosecond laser and a high-power microscope, we have fabricated 3-D structures (1-micron resolution), that can have interesting optical properties, see figure. Opportunities exist to study 3-D photopatterning of various materials including metals, and nanoparticles of metals and oxides. This allows tailoring of the optical and electronic properties of materials. 4) Fluorescent TPA chromophores are of interest for imaging and sensing and we are investigating the effects of solvent, concentration, and electric fields on TPA and fluorescence of conjugated molecules. 5) We have observed a large enhancement of the nonlinear absorption properties of dye molecules dissolved in cyanobiphenyl nematic liquid crystals (LC). Our studies indicate that photoinduced charge transfer from the dye to the LC results in the formation of strongly absorbing radical ions with high efficiency. Current studies are aimed at understanding the role of LC order in the efficiency of charge carrier generation. Other approaches, including the use of fullerene systems, to transient photochromic materials based on charge transfer are being pursued.

Recent Publications

"Two-photon absorption in three-dimensional chromophores based on [2.2]-paracyclophane," G. P. Bartholomew, M. Rumi, S. J. K. Pond, J. W. Perry, S. Tretiak, G. C. Bazan, J. Am. Chem. Soc., 2004, 126 (37): 11529-11542.

"Metal-ion sensing fluorophores with large two-photon absorption cross sections: Aza-crown ether substituted donor-acceptor-donor distyryl benzenes," S. J. K. Pond, O. Tsutsumi, M. Rumi, O. Kwon, E. Zojer, J. L. Brédas, S. R. Marder, J. W. Perry, J. Am. Chem. Soc., 2004 , 126 (30): 9291-9306.

"Two-photon absorption in linear bisdioxaborine compounds - The impact of correlation-induced oscillator-strength redistribution," E. Zojer, W. Wenseleers, M. Halik, C. Grasso, S. Barlow, J. W. Perry, S. R. Marder, J. L. Brédas, Chem. Phys. Chem., 2004, 5 (7): 982-988.

"Limitations of essential-state models for the description of two-photon absorption processes: The example of bis(dioxaborine)-substituted chromophores," E. Zojer, W. Wenseleers, P. Pacher, S. Barlow, M. Halik, C. Grasso, J. W. Perry, S. R. Marder, J. L. Brédas, J. Phys. Chem. B, 2004, 108 (25): 8641-8646.

"Real time differentiation of G-protein coupled receptor (GPCR) agonist and antagonist by two photon fluorescence laser microscopy," M. Y. Cai, M. Stankova, S. J. K. Pond, A. V. Mayorov, J. W. Perry, H. I. Yamamura, D. Trivedi, V. J. Hruby, J. Am. Chem. Soc., 2004, 126 (23): 7160-7161.

"Design and application of high-sensitivity two-photon initiators for three-dimensional microfabrication," S. M. Kuebler, K. L. Braun, W. Zhou, J. K. Cammack, T. Yu, C. K. Ober, S. R. Marder, J. W. Perry, J. Photochem. Photobio. A: Chemistry, 2003, 158, 163-170.

"Ultrabright supramolecular beacons based on self-assembly of two-photon chromophores on metal nanoparticles," F. Stellacci, C. A. Bauer, T. Meyer-Friedrichsen, W. Wenseleers, S. R. Marder, J. W. Perry, J. Am. Chem. Soc., 2003, 125, 328-329.

"Chemically-amplified positive resist system for two-photon three-dimensional lithography," T. Yu, C. K. Ober, S. M. Kuebler, W. Zhou, S. R. Marder, J. W. Perry, Adv. Mat., 2003, 15, 517- 521.

"Bis(dioxaborine) compounds with large two-photon cross sections, and their use in the photodeposition of silver," M. Halik, W. Wenseleers, C. Grasso, F. Stellacci, E. Zojer, S. Barlow, J.-L. BrŽdas, J. W. Perry, S. R. Marder, Chem. Commun., 2003, 1490.

"Information storage and retrieval using Macromol. as storage media," M. Mansuripur, P. K. Khulbe, S. M. Kuebler, J. W. Perry, M. S. Giridhar, J. K. Erwin, K. Seong, S. R. Marder, N. Peyghambarian, Proc. Soc. of Photo-Opt. Instr. Eng., 2003, 5069, 231-243.

"Synthesis and characterization of efficient two-photon acid generators for 3D microfabrication" J. Wang, W. Zhou, K. L. Braun, S. Barlow, S. M. Kuebler, J. W. Perry, S. R. Marder, Polymer Preprints (American Chemical Society, Division of Polymer Chemistry), 2003, 44(1), 970-971.

"Five orders-of-magnitude enhancement of two-photon absorption for dyes on silver nanoparticle fractal clusters," W. Wenseleers, F .Stellacci, T. Meyer-Friedrichsen, T. Mangel, S. R. Marder, J. W. Perry, J. Phys. Chem. B, 2002, 106, 6853-6863.

"Laser and electron-beam induced growth of nanoparticles for 2D and 3D metal patterning," F. Stellacci. C. A. Bauer, T. Meyer-Friedrichsen, W. Wenseleers, V. Alain, S. M. Kuebler, S. J. K. Pond, Y. Zhang, S. R. Marder, J. W. Perry, Adv. Mater., 2002, 14, 194-198.

"Efficient photoacids based upon triarylamine diakylsulfonium salts," W. Zhou, S. M. Kuebler, D. Carrig, J. W. Perry, S. R. Marder, J. Am. Chem. Soc., 2002, 124, 1897-1901.

"Tuning the two-photon absorption response of quadrupolar organic molecules," E. Zojer, D. Beljonne, T. Kogej, H. Vogel, S. R. Marder, J. W. Perry, J. L. Brédas, J. Chem. Phys., 2002, 116, 3646-3658.

"An efficient two-photon photoacids and their applications to 3D microfabrication in positive-tone resists," W. Zhou, S. M. Kuebler, K. L. Braun, T. Yu, J. K. Cammack, C. K. Ober, J. W. Perry, S. R. Marder, J. Am. Chem. Soc., 2002, 124, 1897-1901.

"An efficient two-photon-generated photoacid applied to positive-tone 3D microfabrication," W. Zhou, S. M. Kuebler, K. Braun, T. Yu, J. K. Cammack, C. Ober, J. W. Perry, S. R. Marder, Science, 2002, 296, 1106-1109.

"Role of dimensionality on the two-photon absorption response of conjugated molecules: The case of octupolar compounds," D. Beljonne, E. Zojer, L. Shuai, H. Vogel, W. Wenseleers, J. K. Pond, J. W. Perry, S. R. Marder, J. L. Brédas, Adv. Funct. Mater., 2002, 12, 631-641.

"Photoresponsive hydrogel microstructure fabricated by two-photon initiated polymerization," T. Watanabe, M. Akiyama, K. Totani, S. M. Kuebler, F. Stellacci, W. Wenseleeers, K. Braun, S. R. Marder, J. W. Perry, Adv. Funct. Mater., 2002, 12, 611-614.

"One- and two-photon spectroscopy of donor-acceptor-donor di(styryl)benzene derivatives. Effect of cyano substitution and distortion from planarity," S. J. K. Pond, M. Rumi, M. D. Levin, T. C. Parker, D. Beljonne, M. W. Day, J. L. Brédas, S. R. Marder, J. W. Perry, J. Phys. Chem. A, 2002, 47, 11470-11480.

"Optimizing two-photon initiators and exposure conditions for three-dimensionallithographic microfabrication," S. M. Kuebler, M. Rumi, T. Watanabe, K. Braun, B. H. Cumpston, A. A. Heikal. L. L. Erskine, S. Thayumanavan, S. Barlow, S. R. Marder, J. W. Perry, J. Photopolym. Sci. Tech., 2001, 14, 657-668.

"Quantum-chemical design of two-photon absorbing organic chromophores," D .Beljonne, J. W. Perry, S. R. Marder, J. L. Brédas, Nonlinear Optics, 2001, 27, 47-63.

"Nonlinear Optical Absorption Properties Of Bis-Diarylaminobiphenyl Chromophores," J. E. Ehrlich, S. P. Ananthavel, S. Barlow, K. Mansour, K. Mohanalingam, S. R. Marder, J. W. Perry, M. Rumi, S. Thayumanavan, Nonlinear Optics, 2001, 27, 121-131