One-step fabrication of nanowire-grid polarizers using liquid-bridge-mediated nanotransfer molding
© Park et al.; licensee Springer. 2012
Received: 24 April 2012
Accepted: 27 June 2012
Published: 27 June 2012
Ag nanowire-grid polarizers (NWGPs) were prepared by a one-step fabrication method, called liquid-bridge-mediated nanotransfer molding (LB-nTM). LB-nTM is a new direct nano-patterning method based on the direct transfer of various materials from a mold to a substrate via liquid layer. We fabricated NWGPs with Ag nanowire arrays (81 nm parallel lines and 119 nm spaces) on 2.5 in. transparent substrates by LB-nTM using an Ag nanoparticle solution. The maximum and minimum transmittances of the Ag NWGP at 800 nm were 80% and 10%, respectively.
KeywordsNanowire-grid polarizers Direct printing method Ag nanowire arrays 81.07.Gf Fabrication nanowires 42.79.Ci optical polarizers 81.20.Hy, molding
Polarizer is an indispensable device in a wide range of optical systems, including flat panel displays, microdisplays, and optical networking. Nanowire-grid polarizers (NWGPs) have been of great interest because of their excellent polarization performance and planar structure that allows them to be integrated to other thin-film optoelectronic devices. Moreover, they show good optical stability with respect to variation of the polar angle and azimuthal rotation, and excellent durability at high temperatures and under exposure to high UV flux . The NWGP generally consists of fine grid of parallel metal nanowires with space and width less than the wavelength of light. For the light polarized parallel to the nanowire, it reflects, whereas for the light polarized perpendicular to the nanowire, it transmits. This type of polarizer shows very high extinction ratio between the reflected transverse electric-polarized light and the transmitted magnetic-polarized light over a wide wavelength range and incident angle.
There are several fabrication methods for generating the NWGPs, which include photolithography , e-beam lithography [3–6], laser interference lithography [7, 8], and nanoimprint lithography [9–17]. Among these techniques, nanoimprint lithography is a cost-effective and high-throughput method for the fabrication of metal nanowire grids over a large area, but it suffers from problems. For instance, it involves additional etching or sidewall deposition processes, and continuous fabrication can be difficult because vacuum conditions are required for metal deposition. Recently, we have developed a new direct printing method for generating nanometer-scale patterns of various materials, called liquid-bridge-mediated nanotransfer molding (LB-nTM) . LB-nTM is based on the direct transfer of various materials from a mold to a substrate through a liquid bridge between them. This new technique is capable of generating well-defined large-area nanowire patterns through one step and is well suited for use in automated direct printing machines. LB-nTM is the most efficient method for the fabrication of the wire-grid polarizers at low cost and low environmental impact.
Unless otherwise noted, all commercial materials were obtained from Aldrich Chemical Co. (St. Louis, MO, USA) and used without further purification. The Ag nanoparticle ink (DGP 40LT-15 C) was purchased from Advanced Nano Products (Chungcheongbuk-do, South Korea). The ink contained 20 wt.% silver nanoparticles, with a particle diameter of 40 to 50 nm, dispersed in methanol solvent. PUA (MINS-ERM, Minuta Tech. Co. LTD, Gyeonggi-do, Korea) was used to prepare the UV-curable hard molds. Polydimethylsiloxane (PDMS, Sylgard 184) was ordered from Dow Corning (Dow Corning, Midland, Michigan, USA). Deionized water was purified with a Millipore Milli Q plus system (Billerica, MA, USA), distilled over KMnO4, and then passed through a Millipore Simplicity system.
Preparation of substrates
The flexible substrates employed in this study were cut from polyethylene terephthalate (PET) films (i-components Inc., Seongnam, South Korea). The PET substrates were cleaned with methanol and deionized water, and finally blow-dried with nitrogen to remove the contaminants. The Si substrates used in this research were cut from n-type (100) wafers with resistivity in the range of 1 to 5 Ω·cm. The Si substrates were initially treated by a chemical cleaning process, which involves degreasing, HNO3 boiling, NH4OH boiling (alkali treatment), HCl boiling (acid treatment), rinsing in deionized water, and blow-drying with nitrogen, proposed by Ishizaka and Shiraki, to remove contaminants . A thin oxide layer was grown by placing the Si substrate in a piranha solution (4:1 mixture of H2SO4:H2O2) for 10 to 15 min. The substrate was rinsed several times in deionized water (resistivity = 18 MΩ·cm) then dried with a stream of nitrogen.
The samples were characterized by using a scanning electron microscopy (SEM, Hitachi S4800, Hitachi, Ltd., Chiyoda, Tokyo, Japan) at 15 kV and a UV–vis spectrometer (Agilent 8453 UV–vis, Agilent Technologies Inc., Santa Clara, CA, USA).
Results and discussion
In summary, we described a one-step fabrication of an Ag NWGP using LB-nTM. Ag nanowire arrays, produced by LB-nTM using an Ag-particle solution, exhibited fine fidelity with a high aspect ratio (approximately 1.73). The Ag NWGPs were fabricated on 2.5 in. PET substrates and showed a high transmission and a contrast ratio for the range of visible light. This method is an ideal fabrication technique for automated direct printing machines that produce large area NWGPs on diverse substrates with no additional steps.
This work was supported by a grant from the National Research Foundation (NRF) funded by the Korea government (MEST) (No. 2011–0029811), a grant from the Global Frontier R&D Program at the Center for Multiscale Energy System funded by the National Research Foundation (No. 2011–0031562) and by a Global Ph. D. Fellowship funded by NRF (No. 2011–0007507).
- Wang JJ, Walters F, Liu X, Sciortino P, Deng X: High-performance, large area, deep ultraviolet to infrared polarizers based on 40 nm line/78 nm space nanowire grids. Appl Phys Lett 2007, 90: 061104. 10.1063/1.2437731View ArticleGoogle Scholar
- Yamada I, Takano K, Hangyo M, Saito M, Watanabe W: Terahertz wire-grid polarizers with micrometer-pitch Al gratings. Opt Lett 2009, 34: 274–276. 10.1364/OL.34.000274View ArticleGoogle Scholar
- Tamada H, Doumuki T, Yamaguchi T, Matsumoto S: Al wire-grid polarizer using the s-polarization resonance effect at the 0.8-μm-wavelength band. Opt Lett 1997, 22: 419–421. 10.1364/OL.22.000419View ArticleGoogle Scholar
- Schnabel B, Kley EB, Wyrowski F: Study on polarizing visible light by subwavelength-period metal-strip gratings. Opt Eng 1999, 38: 220–226. 10.1117/1.602257View ArticleGoogle Scholar
- Clausnitzer T, Fuchs H-J, Kley E-B, Tuennermann A, Zeitner U: Polarizing metal stripe gratings for a micro-optical polarimeter. Proc SPIE 2003, 5183: 8–15.View ArticleGoogle Scholar
- Wcber T, Fuchs H, Schmidt H, Kley E, Tünnermann A: Wire-grid polarizer for the UV spectral region. Proc SPIE 2009, 7205: 720504.View ArticleGoogle Scholar
- Kim SH, Park J, Lee K: Fabrication of a nano-wire grid polarizer for brightness enhancement in liquid crystal display. Nanotechnology 2006, 17: 4436–4438. 10.1088/0957-4484/17/17/025View ArticleGoogle Scholar
- Lee JH, Song Y, Lee J, Ha J, Hwang KH, Zang D: Optically bifacial thin-film wire-grid polarizers with nano-patterns of a graded metal-dielectric composite layer. Opt Express 2008, 16: 16867–16876. 10.1364/OE.16.010867View ArticleGoogle Scholar
- Wang J, Schablitsky S, Yu Z, Wu W, Chou SY: Fabrication of a new broadband waveguide polarizer with a double-layer 190 nm period metal-gratings using nanoimprint lithography. Technol. B 1999, 17: 2957–2960. 10.1116/1.590933Google Scholar
- Wang J, Sun X, Chen L, Zhuang L, Chou SY: Molecular alignment in submicron patterned polymer matrix using nanoimpritng lithography. Appl Phys Lett 2000, 77: 166–168. 10.1063/1.126912View ArticleGoogle Scholar
- Ahn S, Lee K, Kim J, Kim SH, Park J, Lee S, Yoon P: Fabrication of a 50 nm half-pitch wire grid polarizer using nanoimprint lithography. Nanotechnology 2005, 16: 1874–1877. 10.1088/0957-4484/16/9/076View ArticleGoogle Scholar
- Wang JJ, Chen L, Liu X, Sciortino P, Liu F, Walters F, Deng X: 30-nm-wide aluminum nanowire grid for ultrahigh contrast and transmittance polarizers made by UV-nanoimprint lithography. Appl Phys Lett 2006, 89: 141105. 10.1063/1.2358813View ArticleGoogle Scholar
- Wang JJ, Zhang W, Deng X, Deng J, Liu F, Sciortino P, Chen L: High-performance nanowire-grid polarizers. Opt Lett 2005, 30: 195–197. 10.1364/OL.30.000195View ArticleGoogle Scholar
- Ahn SH, Kim JS, Guo LJ: Bilayer metal wire-grid polarizer fabricated by roll-to-roll nanoimprint lithography on flexible plastic substrate. J. Vac. Sci. Technol. B 2007, 25: 2388–2391. 10.1116/1.2798747View ArticleGoogle Scholar
- Chen L, Wang JJ, Walters F, Deng X, Buonanno M, Tai S, Liu X: Large flexible nanowire grid visible polarizer made by nanoimprint lithography. Appl Phys Lett 2007, 90: 063111. 10.1063/1.2472532View ArticleGoogle Scholar
- Ahn SH, Guo LJ: High-speed roll-to-roll nanoimprint lithography on flexible plastic substrates. Adv Mater 2008, 20: 2044–2049. 10.1002/adma.200702650View ArticleGoogle Scholar
- Ge Z, Wu S: Nanowire grid polarizer for energy efficient and wide-view liquid crystal displays. Appl Phys Lett 2008, 93: 121104. 10.1063/1.2988267View ArticleGoogle Scholar
- Hwang JK, Cho S, Dang JM, Kwak EB, Song K, Moon J, Sung MM: Direct nanoprinting by liquid-bridge-mediated nanotransfer moulding. Nat. Nanotech 2010, 5: 742–748. 10.1038/nnano.2010.175View ArticleGoogle Scholar
- Jackman RJ, Duffy DC, Ostuni E, Willmore ND, Whitesides GM: Fabricating large arrays of microwells with arbitrary dimensions and filling them using discontinuous dewetting. Anal Chem 1998, 70: 2280–2297. 10.1021/ac971295aView ArticleGoogle Scholar
- Lee BH, Cho YH, Lee H, Lee K, Kim SH, Sung MM: High-resolution patterning of aluminum thin films with a water-mediated transfer process. Adv Mater 2007, 19: 1714–1718. 10.1002/adma.200601884View ArticleGoogle Scholar
- Lee BH, Sung MM: Patterning a two-dimensional colloidal crystal by water-mediated particle transfer printing. Chem Mater 2007, 19: 5553–5556. 10.1021/cm071128jView ArticleGoogle Scholar
- Lee BH, Lee K, Kim SH, Sung MM: Patterning aluminum thin films by water-mediated nano-transfer printing. J. Korean Phys. Soc 2007, 51: S203-S206. 10.3938/jkps.51.203View ArticleGoogle Scholar
- Oh K, Lee BH, Lee KH, Im S, Sung MM: Water-mediated Al metal transfer printing with contact inking for fabrication of thin-film transistors. Small 2009, 5: 558–561. 10.1002/smll.200801108View ArticleGoogle Scholar
- Ishizaka A, Shiraki Y: Low-temperature surface cleaning of silicon and its application to silicone MBE. J Electrochem Soc 1986, 133: 666–671. 10.1149/1.2108651View ArticleGoogle Scholar
- Kim J, Lee K, Ahn S, Kim SH, Park J, Lee S, Yoon S: Fabrication of nanowire polarizer by using nanoimprint lithography. J. Korean Phys. Soc 2004, 45: S890-S892.Google Scholar
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