Name: nanomoulding of functional materials, a versatile complementary pattern replication method to nanoimprinting
Uploaded: 2013-01-23T12:00:00
Description: Watch this Scientific Journal Video about Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting at JoVE.com

The authors thank M. Leboeuf for assistance with the AFM, W. Lee for the anodically textured aluminum master and the Swiss Federal Energy Office and the Swiss National Science Foundation for funding. A part of this work was carried out in the framework of the FP7 project "Fast Track" funded by the EC under grant agreement no 283501.

1. Mould Fabrication
We use our home-built nanoimprinting setup for the fabrication of the negative mould following Ref. 6, but any alternative nanoimprinting setup will work fine. Alternatively a functionalized polydimethylsiloxane (PDMS) mould might also work.
<ol>
 <li>Fabricate or buy a suitable master carrying the nanoscale pattern to be transferred. In principle, any master suitable for nanoimprinting will do the job. We use a textured ZnO layer on a glass sheet (Schott, AF3...

<ol>
	<li>Geissler, M., Xia, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patterning:+Principles+and+Some+New+Developments.">Patterning: Principles and Some New Developments.</a> Advanced Materials. 16 (15), 1249-1269 (2004).</li><li>Guo, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoimprint+Lithography:+Methods+and+Material+Requirements.">Nanoimprint Lithography: Methods and Material Requirements.</a> Advanced Materials. 19, 495-513 (2007).</li><li>Ahn, S. H., Guo, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-Area+Roll-to-Roll+and+Roll-to-Plate+Nanoimprint+Lithography:+A+Step+toward+High-Throughput.">Large-Area Roll-to-Roll and Roll-to-Plate Nanoimprint Lithography: A Step toward High-Throughput.</a> Application of Continuous Nanoimprinting. ACS Nano. 3 (8), 2304-2310 (2009).</li><li>Battaglia, C., Escarr&#233;, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoimprint+Lithography+for+High-Efficiency+Thin-Film+Silicon+Solar+Cells.">Nanoimprint Lithography for High-Efficiency Thin-Film Silicon Solar Cells.</a> Nano Letters. 11, 661-665 (2011).</li><li>Battaglia, C., Escarr&#233;, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanomoulding+of+Transparent+Zinc+Oxide+Electrodes+for+Efficient+Light+Trapping+in+Solar+Cells.">Nanomoulding of Transparent Zinc Oxide Electrodes for Efficient Light Trapping in Solar Cells.</a> Nature Photonics. 5, 535-538 (2012).</li><li>Escarr&#233;, J., S&#246;derstr&#246;m, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+Fidelity+Transfer+of+Nanometric+Random+Textures+by+UV+Embossing+for+Thin+Film+Solar+Cells+Applications.">High Fidelity Transfer of Nanometric Random Textures by UV Embossing for Thin Film Solar Cells Applications.</a> Solar Energy Materials &amp; Solar Cells. 95, 881-886 (2011).</li><li>Fa&#255;, S., Feitknecht, L., Schl&#252;chter, R., Kroll, U., Vallat-Sauvain, E., Shah, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rough+ZnO+layers+by+LP-CVD+process+and+their+effect+in+improving+performances+of+amorphous+and+microcrystalline+silicon+solar+cells.">Rough ZnO layers by LP-CVD process and their effect in improving performances of amorphous and microcrystalline silicon solar cells.</a> Solar Energy Materials and Solar Cells. 90, 2960-2967 (2006).</li><li>Zhao, X. -. M., Xia, Y., Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+Three-Dimensional+Micro-Structures:+Microtransfer+Molding.">Fabrication of Three-Dimensional Micro-Structures: Microtransfer Molding.</a> Advanced Materials. 8, 837-840 (1996).</li><li>Hampton, M. J., Williams, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Patterning+of+Sub-500+nm+Inorganic+Oxide+Structures.">The Patterning of Sub-500 nm Inorganic Oxide Structures.</a> Advanced Materials. 20, 2667-2673 (2008).</li><li>Bass, J. D., Schaper, C. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transfer+Molding+of+Nanoscale+Oxides+Using+Water-Soluble+Templates.">Transfer Molding of Nanoscale Oxides Using Water-Soluble Templates.</a> ACS Nano. 5 (5), 4065-4072 (2011).</li><li>Escarr&#233;, J., Nicolay, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanomoulded+front+ZnO+contacts+for+thin+film+silicon+solar+cell+applications.">Nanomoulded front ZnO contacts for thin film silicon solar cell applications.</a> , (2012).</li><li>Sontheimer, T., Rudigier-Voigt, E., Bockmeyer, M., Klimm, C., Schubert-Bischoff, P., Becker, C., Rech, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-area+fabrication+of+equidistant+free-standing+Si+crystals+on+nanoimprinted+glass.">Large-area fabrication of equidistant free-standing Si crystals on nanoimprinted glass.</a> Phys. Status Solidi. RRL. 5, 376-379 (2011).</li></ol>

Nanomoulding allows the transfer of nanopatterns on arbitrary functional materials. Comparison of the individual processing steps in Figure 1 and 2 reveals the close relationship between nanomoulding and nanoimprinting. The major difference between nanomoulding and nanoimprinting is the additional material deposition step in Figure 2e. The remaining process flow is identical. Nanomoulding can therefore be performed on any available nanoimprinting setup.
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Nanopatterning has gained tremendous importance in many fields of nanotechnology and applied sciences. Pattern generation is the first step and may be accomplished by top-down approaches such as electron-beam lithography or bottom-up approaches based on self-assembly methods such as nanosphere lithography or block copolymer lithography 1. As important as pattern generation is pattern replication. Besides photolithography, nanoimprinting (Figure 1) has emerged as a promising alternative in particular suitable for high-throughput large-area nanoscale patterning at low cost 2-4. While photolithography requires a patterned mask, nanoimprinting relies on a prefabricated master structure. Pattern transfer from the master is commonly performed into a thermoplastic or a UV- or thermally curable polymer. However there are many cases, where it is desirable to transfer the pattern directly onto a functional material.
Here we describe a replication method based on nanomoulding and layer transfer (Figure 2) which we recently introduced in Ref. 5 to transfer nanoscale patterns onto functional zinc oxide electrodes. Our nanomoulding method can be easily implemented if a nanoimprinting setup is available. Nanomoulding offers the potential to be generalized to many other functional materials, materials stacks and even complete devices, provided that the mould material is chosen such that it is compatible with the material deposition process(es). As an example we present here nanomoulding of transparent conductive zinc oxide (ZnO) electrodes deposited by chemical vapor deposition (CVD) which find their application to enhance light trapping in solar cells 5.

<table border="1">
 <tbody>
 <tr>
 <td>Name of the Reagent</td>
 <td>Company</td>
 <td>Catalogue Number</td>
 <td>Comments (optional)</td>
 </tr>
 <tr>
 <td>Nanoimprinting resin</td>
 <td>Microresist</td>
 <td>Ormostamp</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>(1H, 1H, 2H, 2H-Perfluoroctyl)-trichlorsilane, anti-adhesion agent</td>
 <td>Sigma Aldrich</td>
 <td>448931-10G</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Glass slides</td>
 <td>Schott</td>
 <td>AF32 eco</td>
 <td>0.5 mm</td>
 </tr>
 <tr>
 <td>Polyethylene naphtalate (PEN) sheets</td>
 <td>Goodfellow</td>
 <td>ES361090</td>
 <td>0.125 mm</td>
 </tr>
 <tr>
 <td>(C2H5)2Zn</td>
 <td>Akzo Nobel</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Ag sputter target 4N</td>
 <td>Heraeus</td>
 <td>81062165</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>B2H6, SiH4, H2, B(CH3)3, PH3, CH4, CO2</td>
 <td>Messer</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>EQUIPMENT</td>
 </tr>
 <tr>
 <td>Nanoimprinting system</td>
 <td>Home-built</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>LP-CVD system</td>
 <td>Home-built</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>PVD system</td>
 <td>Leybold</td>
 <td>Univex 450 B</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>PE-CVD reactor</td>
 <td>Indeotec</td>
 <td>Octopus I</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>SEM</td>
 <td>JEOL</td>
 <td>JSM-7500 TFE</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>AFM</td>
 <td>Digital Instruments</td>
 <td>Nanoscope 3100</td>
 <td>&nbsp;</td>
 </tr>
 </tbody>
</table>

nanomoulding of functional materials, a versatile complementary pattern replication method to nanoimprinting

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding combined with layer transfer enables the replication of arbitrary surface patterns from a master structure onto the functional material. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes. In particular we demonstrate the fabrication of patterned transparent zinc oxide electrodes for light trapping applications in solar cells.

Figure 3 summarizes some illustrative examples of nanomoulded structures. A ZnO master structure grown by CVD on glass is shown in (a). The corresponding nanomoulded ZnO replica is shown in (d). Comparison of the local height (g) and angle (j) histograms extracted from AFM images reveal the high fidelity of the nanomoulding process. Analogous results are shown for a one-dimensional grating fabricated by interference lithography (b,e,h,k) and anodically textured aluminum (c,f,i,l).
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Watch this Scientific Journal Video about Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting at JoVE.com

Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes.

We describe a nanomoulding technique which  allows low-cost nanoscale patterning of functional materials, materials stacks  and full devices. Nanomoulding ...

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