2022python代写纳米压印光刻技术
纳米压印光刻技术-诱导自对准液晶取向层新型工具-指导essay Nanoimprinting Lithography as Novel Tool Inducing Self-AlignedLiquid Crystals For Alignment LayerHuang-Ming Philip Chen*Department of Photonics and Display Institute, National Chiao Tung UniversityRm. 506, MIRC Building, 1001 Ta Hsueh Road, Hsin-Chu 30010, Taiwan, R.O.CChih-Ho Chiu, Hui-Lung Kuo, Pin-Cheng Chen, Chun-Hsiang Wen and Yi-Chun LiuMaterials Research Labs. of Industrial Technology Research InstituteB77, 195-5 Chung-Hsin Rd. sec. 4, Chutung, Hsin-Chu 310, Taiwan, ROC.AbstractPolymerizable nematic liquid crystal (LC) was applied as resistfor our newly developed nanoimprinting lithography process.The LC resist was self-aligned during imprinting process at verylow impriting pressure, 1.5 bar and the patterned area was ableto achieve 4×4 cm2. The optical anisotropic was verified throughpolarized optical microscopy (POM). The various thickness ofLC resist was evaluated and compared alignment ability withpolyimide, and isotropic resists.微磨碎LC薄膜准备通过这种新颖的方法提供了新的应用液体LC细胞内晶体对准层以及制备的光学各向异性的技术。The micro-grated LC filmsprepared by this novel method offer new applications for liquidcrystal as alignment layer within LC cells as well as preparationof optical anisotropic films. http://www.ukassignment.org/dxessay/1. Introduction液晶（LC）对准层是形成高性能的LC细胞关键因素之一。Liquid crystal (LC) alignment layer is one of the key elements informing high performance LC cells. LC alignment layers can beprepared by contact, i.e. mechanical buffing,[1] and non-contact,such as photoinduced surface alignment techniques.[2] Up-todate,mechanical buffing still dominates the mainstream LC cellpreparation due to polyimide (PI) layer yields robust and uniformalignment ability under mechanical buffing.[3-5] Studies haveshown that Nanoimprint lithography (NIL) applications are able tocreate surface relief patterns.[6-9] In particular, certaindirectional order of light emitting molecules has beendemonstrated on the surface of submicron patterned polymermatrix.[10] All patterned polymer matrix mentioned above weremainly made from amorphous materials with relatively highimprinting pressure.[11] Here we我们提出一种新颖的液晶印迹压力。对准技术，在此我们利用液晶的印迹抵抗，可以自对准没有预涂对齐层1.5印记下在大面积上的4×4平方厘米的压力。report a novel liquid crystalalignment technique, in which we utilize liquid crystal asimprinting resist that can be self-aligned under 1.5 bar imprintingpressure on a large area of 4×4 cm2 without pre-coated alignmentlayer. Hence, the novel alignment technique has great potentialfor future liquid crystal cell fabrication and optical anisotropicfilm preparation.2. ExperimentsThe new NIL process creating alignment surface is depicted inScheme 1.不同音高的模具压印通过电子束光刻或光刻制造。Molds with different pitches for the imprinting stepwere fabricated by E-beam lithography or photolithography.The pitches were from 1.8 to 0.35μ m with the line/space ratiosfrom 0.4 to 2. A toluene solution, comprising SLM-90519(reactive liquid crystal oligomer, Wacker Chemical) and Irgacure369 (photo-initiator, Ciba),准备为LC抵制和LC聚合物薄膜。标准压印工艺条件是1.5巴的印迹压力120℃，20分钟LC抗蚀剂，然后通过紫外线照射。was prepared for both LC resist andLC polymer films. The standard imprinting process condition is1.5 bar of imprinting pressure at 120 oC for 20 minutes on LCresist, followed by UV irradiation. To ease the peel-off processfrom the mold, N-dodecyltrichlorosilane was applied as areleasing agent (purchased from TCI). Molds were immersed inthe mixture of n-trichlorosilane and toluene under nitrogen for onehour. After releasing, these molds were rinsed with toluene anddried by a stream of nitrogen. The post-baked procedure forreleasing film from molds was done at 150 oC for 3 mins afterimprinting process.Scheme 1. NIL fabrication for surface microstructures using LC asresist.3. Results and DiscussionThe direct evidence in Figure 1 suggests that the novel NILprocess is capable of aligning LC resist. A 4 x 4 cm2 patternedarea which prepared by the mold of 1.8μ m/period and 200nm indepth showed optical anisotropy under polarizing opticalmicroscope (POM). Light transmission was fully dependent onthe azimuthal angle of patterned area under crossed polarizers.The results in Figure 1 clearly showed light blockage (dark state)in the patterned area, when grating lines were paralleled to one ofthe polarizers’ axes. The maximum light transmission (brightstate) occurred when grating lines of the patterned area are placedat either 45o or 135o. In all cases above, un-patterned areaappeared in all azimuthal angles showed the Grandjean textureonly. The driving force for self-aligned LC resist can beattributed to the laminar flow and capillary effect during the hotpressing inside the mold. This mechanical pressing inducedvarious shear rate distribution which yielded the preferredorientation along the flow direction. [12]Figure 1. Pictures of the liquid crystal grating film under POM.(a) grating line direction is parallel (0o) to the axis of polarizer,and (b) at 45o.The order parameter is also strongly affected by thickness of LCresist and depth of mold. Various thickness of resist wasexamined by mold with 1.8 μm/period and 200nm in depth. Asshown in Figure 2, the concentration of resist needs to be greaterthan 5.0 weight percent solution (240 nm in film thickness) toshow good molecular order. This result implies that thethickness of resist needs to be greater than mold’s depth to obtainbest result.Order ParameterFigure 2. Order parameter on different thickness of LC resist.Polymerizable nematic liquid crystal (SLM-90519), the samematerial utilized for LC grating film, was doped with S-428dichroic dye (Mitsubishi Chemical) as an order indicator forevaluation. The dye-doped LC layer was prepared into 3.6±0.3μm thick films by spin coating. The order parameter, S, isdetermined by the absorption of A⊥ and A‖ at 500 nm of thewavelength using the equation ( ) ( 2 ) C C S = A − A A + A ⊥ ⊥ .[13]The high order parameter, S = 0.62, can be achieved on 1.7 μmLC grating film, which was comparable to the PI buffed surface (S= 0.67), but much better than the one using isotropic grating film(S = 0.33), as shown in Figure 3. This result suggests that theLC grating film possesses a similar alignment capability,comparing with the PI buffed surface. The pretilt angle of LC onpolyimide, LC grating film, and isotropic grating film weremeasured based on crystal rotation method and found to be 1.7,Wavelength, nmFigure 3 Linear dichroism of LC with dichroic dye (S-428) on LCgrating film, isotropic grating film and PI treated alignment layer.Both Desolite 4D5-57 and SLM-90519 grating films showed thesame relief pattern under NIL treatment. In Figure 4, the LCmolecules on LC grating film, however, has better extinction ratiothan isotropic grating film at all annealing and curingtemperatures.液晶分子的上各向同性光栅膜透露有限的择优取向，由于它们的分子约束微槽表面上。LC molecules on isotropic grating film revealedlimited preferred orientation, due to their molecular confinementon the micro-groove surfaces. In addition to the confinementeffect, the order of LC molecules on LC grating film wasenhanced by molecular arrangement. The self-aligned sample ofSLM-90519, however, possesses a greater degree of molecularalignment ability, which is absent in an isotropic sample ofDesolite 4D5-57. This is the reason why LC on SLM-90519 hasmuch higher order parameter than the LC on Desolite 4D5-57.These results suggest that micro-groove surfaces can induce thealignment ability of liquid crystalline materials. Molecularlevel’s alignment, however, is the key to achieve well orderedliquid crystals.4. ConclusionThe novel NIL technique for LC alignment was successfullyachieved in this study.没有任何预取向层，这简单的方法，可以有效地调整LC。Without any pre-alignment layer, thissimple approach can align LC effectively. Specifically,施加低压印压力液晶抵抗1.5bar ，产生以自对准的光栅膜，是非常容易在实际中操作。applyinglow imprinting pressure at 1.5 bar on liquid crystal resist, yieldinga self-aligned grating film, is much easier to operate in practicalsense. Furthermore, LC resist possesses aligning capability canalso be utilized as an alignment layer itself. The results indicatethat a good liquid crystal alignment can not solely depend on thegrooved surface, but rather rely on the molecular level of surfacealignment ability.#p#分页标题#e#5. AcknowledgementsThe funding of this work was provided by the MOEA of theRepublic of China under the frontier research program and waspartially supported by MOEA Technology Development forAcademic Project # 94-EC-17-A-07-S1-046.6. References[1] Alignment of Liquid crystals and Their Mixtures, Ed: J.Cognard (Gorden & Breach, London, 1982).[2] a) M. O’Neill and S. M. Kelly, J. Phys. D: Appl. Phys. 33,R67 (2000). b) J. Hoogboom, M. Behdani, J. A. A. W.Elemans, M. A. C. Devillers, R. de Geder, A. E. Rowan, T.Rasing, and R. J. M. Nolte, Angew. Chem. Int. Ed. 42, 1812(2003).[3] M. Schadt, Nature 381, 212 (1996).[4] P. Chaudhari, J. A. Lacey, S-C. A. Lien, and J. L. Speidell,Jpn. J. Appl. Phys. 37, L55 (1998).[5] P. Chatelaine, Bull. Soc. Franc. Crist. 66, 105 (1943).[6] a) S.Y. Chou, P. R. Krauss, and P. J. Renstrom, Appl. Phys.Lett. 67, 3114 (1995). b) S. Y. Chou, P. R. Krauss, and P. J.Renstrom, Science 272, 85 (1996).[7] Y. Hirai, M. Fujiwara, T. Okuno, T. Tanaka, M. Endo, S. Irie,K. Nakagawa, and M. Sasago, J. Vac. Sci Technol. B. 19,2811 (2001).[8] S-R. Kim, A. I. Teixeira, P. F. Nealy, A. E. Wendt, and N. L.Abbott, Adv. Mater. 14, 1468 (2002).[9] H-L. Kuo, C-H. Chiu, and P-C. Chen “A wire-grid polarizer”,presented at Int. Conf. on Society for Information DisplaySeattle, USA, Poster # P-122, May 25-27, (2004).[10] J. Wang, X. Sun, L. Chen, and S. Y. Chou, Appl. Phys. Lett.77, 166 (2000).[11] F. Gottschalch, T. Hoffmann, C. M. S. Torres, H. Schulz, H.C. Scheer, Solid State Electron. 43, 1079 (1999).[12] a) The Physics of Liquid Crystals, Eds: P. G. de Gennes and J.Prost (Oxford University Press, New York, 1993). b) Z.Chen, J. A. Kornfield, S. D. Smith, J. T. Goothaus, and M.M. Satkowshi, Science 277, 1248 (1997). c) P. T. Callaghan,M. L. Kilfoil, and E. T. Samulski, Phys. Rev. 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