The method presented here illustrates a synthetic route that has been developed for the growth of uniaxially aligned ExperimentalThe starting materials for reaction precursors were cobalt nitrite (Co(NO) 3´6 H 2 O, 98 %, Sigma±Aldrich), iron chloride (FeCl 2´4 H 2 O, 99 %, Sigma±Aldrich), oxalic acid (H 2 C 2 O 4 , 99 %, Sigma±Aldrich), cyclohexane (Sigma±Aldrich), n-pentanol (Sigma±Aldrich), and cetyltrimethylammonium bromide (CTAB, Sigma±Aldrich). In a typical synthesis, a quaternary microemulsion consisting of CTAB/water/cyclohexane/n-pentanol was prepared by dissolving CTAB (2.5 g) in a mixture of 75 mL of cyclohexane and 2.5 mL of n-pentanol. The resulting solution was stirred for 20 min. Subsequently, 3.75 mL of an 0.8 M H 2 C 2 O 4 aqueous solution was added into the above solution and the mixture was stirred for an additional 45 min. Finally, 1.25 mL of an aqueous solution containing 0.05 M Co(NO) 3´6 H 2 O and 0.1 M FeCl 2´4 H 2 O was added to the above microemulsion and stirred for 24 h at room temperature. The solid product was recovered by centrifugation and was dried in air at ambient temperature. The solid product was then heated from 100 to 720 C for 2.5 h and annealed at 720 C for another 3 h to obtain the final product. Room-Temperature, Low-Pressure Nanoimprinting Based on Cationic Photopolymerization of Novel Epoxysilicone Monomers** By Xing Cheng, L. Jay Guo,* and Peng-Fei Fu* Nanoimprint lithography (NIL) [1±3] is an emerging lithographic technique that promises high-throughput patterning of nanostructures with great precision. [4,5] The simplicity and high resolution provided by this technique have found numerous applications in electronics, such as in hybrid plastic electronics, [6] organic thin-film transistors and electronics, [7,8] and nanoelectronic devices in Si [9,10] and GaAs; [6,11] in photonics, such as in organic lasers, [12] pixels of high-resolution organic light-emitting diodes, [13] diffractive optical elements, [14] waveguide polarizers, [15] and active [16] and nonlinear optical polymer nanostructures; [17] in magnetic devices, like high-density quantized magnetic discs, [18] and patterned magnetic media; [19] as well as in biological applications, such as manipulating DNA in nanofluidic channels [20±22] and nanoscale protein pat-COMMUNICATIONS

Nanoimprint lithography (NIL) is a patterning technique that has emerged as one of the most promising technologies for high-throughput nanoscale replication. [1,2] Several applications in electronics, photonics, magnetic devices, and the biological field have been developed using this simple, low-cost, and high-resolution technique. In the biological field, DNA, [3] proteins, [4][5][6] and guides for molecular motors have been patterned; [7] nanowire arrays have been fabricated for electronic applications; [8] new magnetic devices, such as patterned magnetic media [9,10] and high density quantized magnetic discs, [11] have been engineered; and wire grid polarizers, [12,13] lightemitting diodes, [14,15] and diffractive optical elements [16] have been developed for photonics. The success of NIL as a next generation lithographic technique strongly depends on the research for new materials that are better suited as the nanoimprint resist. Because imprint lithography makes a conformal replica of surface relief patterns by mechanical embossing, the resist materials used in imprinting should be deformed easily under an applied pressure. The most commonly used materials in the original NIL scheme are thermal plastic polymers, which become viscous fluids when heated above their glass transition temperatures (T g ). However the viscosity of the heated polymers is typically high and thus the imprinting process requires significant pressure. In addition, these thermal plastic resists normally have a high tendency to stick to the mold because of non-optimized chemistry and orientation of the polymer backbone structures, which seriously affects the fidelity and quality of the pattern definition. Furthermore they do not offer the necessary etch resistance. Therefore, a nanoimprint resist system with combined mold-release and etch-resistance properties that allows fast and precise nanopatterning is highly desirable.Thermally curable monomers are very attractive materials for nanoimprint applications because they present in the liquid state, making it possible for them to be imprinted in a short period of time under low pressure and temperature, in sharp contrast to thermal plastic polymers. As one of these materials, poly(dimethylsiloxane) (PDMS) has previously been used by several research groups for micropatterning, mainly in the context of soft lithography, [17][18][19][20][21] and has found numerous applications in fields as diverse as microelectrochemical systems (MEMS), biotechnology, photonics, and nanoelectronics. In addition to its well known transparency to UV and visible light along with its good biocompatibility, it has a low surface energy (18-21 mN m -1 ) [22] that allows easy mold release without causing any structural damage to the imprinted structures; moreover, it posses a high resistance to oxygen plasma because of a higher silicon content. However, the PDMS material made from commercial Sylgard 184 as precursor is not suitable for nanoimprint applications because of two significant drawbacks. Firstly, its cur...

Epoxysilsesquioxane (SSQ)-based materials have been developed as patterning layers for large-area and high-resolution nanoimprinting. The SSQ polymers, poly(methyl-co-3-glycidoxypropyl) silsesquioxanes (T(Me)T(Ep)), poly(phenyl-co-3-glycidoxypropyl) silsesquioxanes (T(Ph)T(Ep)), and poly(phenyl-co-3-glycidoxypropyl-co-perfluorooctyl) silsesquioxanes (T(Ph)T(Ep)T(Fluo)), were precisely designed and synthesized by incorporating the necessary functional groups onto the SSQ backbone. The materials possess a variety of characteristics desirable for NIL, such as great coatability, high modulus, good mold release, and excellent dry etch resistance. In particular, the presence of epoxy functional groups allows the resists to be solidified within seconds under UV exposure at room temperature, and the presence of the fluoroalkyl groups in the SSQ resins greatly facilitate mold release after the imprint process. In addition, the absence of metal in the resins makes the materials highly compatible with applications involving Si CMOS integrated circuits fabrication.

Presented here is the novel use of thermoplastic siloxane copolymers as nanoimprint lithography (NIL) resists for 60 nm features. Two of the most critical steps of NIL are mold release and pattern transfer through dry etching. These require that the NIL resist have low surface energy and excellent dry‐etching resistance. Homopolymers traditionally used in NIL, such as polystyrene (PS) or poly(methyl methacrylate) (PMMA), generally cannot satisfy all these requirements as they exhibit polymer fracture and delamination during mold release and have poor etch resistance. A number of siloxane copolymers have been investigated for use as NIL resists, including poly(dimethylsiloxane)‐block‐polystyrene (PDMS‐b‐PS), poly(dimethylsiloxane)‐graft‐poly(methyl acrylate)‐co‐poly(isobornyl acrylate) (PDMS‐g‐PMA‐co‐PIA), and PDMS‐g‐PMMA. The presence of PDMS imparts the materials with many properties that are favorable for NIL, including low surface energy for easy mold release and high silicon content for chemical‐etch resistance—in particular, extremely low etch rates (comparable to PDMS) in oxygen plasma, to which organic polymers are quite susceptible. These properties give improved NIL results.

A simple procedure for duplicating original nanoimprint masters was developed by using a new fluorinated photocurable silsesquioxane (SSQ) resin cast on either hard or flexible substrates. With an appropriate viscosity, this resin can be spin coated on the substrate, and the original SiO2 masters easily replicated in this resin by using a low pressure nanoimprinting process. The resin has a sufficient modulus in its cured state, which makes it suitable for nanoimprinting other polymeric materials. Due to the high thermal stability and UV transparency of SSQ materials, such a stamp can be used for both UV and thermal nanoimprinting. Furthermore, the fluoroalkyl groups contained in the silsesquioxane resin provide the low surface energy necessary for easy demolding after nanoimprinting. These features combined make the material an excellent candidate to fabricate a multitude of duplicates from an original nanoimprint lithography master for mass fabrication.