The authors would like to thank to Heraeus Precious Metals GmbH &amp; Co. KG for their support and supply of commercial silver pastes, especially M. K&#246;nig for fruitful discussions. Special thanks go to M. Schmalz for experimental support. C. Y&#252;ce gratefully acknowledges financial support by the 100 prozent erneuerbar stiftung. Finally, we acknowledge financial support from the Federal Ministry for Economic Affairs and Energy (Grant no. 0325775G).

<ol>
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The authors have nothing to disclose.

高度に濃縮された懸濁液またはペーストの包括的なレオロジー特徴付けは、このような複雑な流体の処理及び塗布時ターゲット製品開発会議マニホールド要件のために必須です。この調査は、大きな変形や破断点伸びならびにフィラメント間に引張力延伸後の降伏応力、粘度、壁スリップ速度、構造回復の決意を含みます。すべての要約は、本方法を適用した情報を取得し、及びペースト特性を表1にまとめます。 平行平板レオメトリー回転の壁滑り、剪断バンディングとサンプルスピルオーバーを示す高度に充填された懸濁液のレオロジー量の信頼性が決意するためのビデオ記録の重要性が実証されます。ビデオ録画は、適切なマーカーを使用してサンプルリムにおける真の変形形状の決意と流れ場を可能にします。それはnecessですレオロジー実験の結果を分析する前に、この変形挙動を研究するためにARY。従って、測定パラメータの設定及び粗さの値をプレート粘度測定が可能であるために識別することができます。ペーストの降伏応力は、適切な粗さのベーンジオメトリまたはプレート - プレートジオメトリーを使用してのいずれかで決定することができます。 粘度決意は、サンプル組成に応じて慎重に選択されたプレートの粗さを有するプレート - プレートジオメトリを使用して可能です。高い粗さは、必ずしも下壁スリップにはなりません。粘度決意を行うことが可能な剪断速度または剪断応力の範囲は、降伏応力及び試料流出の開始によって制限されます。 また、滑り速度を直接測定することができ、栓流、剪断バンディングまたはサンプルスピルオーバーが発生する測定条件を明確に識別することができます。壁スリップ測定のために滑らかな表面は、上部剪断PLAとして使用しましたTEのみ上部プレートの滑りを可能にするためにラフ底板。このスリップ速度は、上部プレートの角速度から直接計算することができます。両方のペーストのために滑りが良く見かけの降伏応力下のストレスレベルで発生します。同様の観察は、ガラスビーズ25、27粘土懸濁液、ソフトミクロゲルペースト並びに乳剤28、29、30のための懸濁液のために報告されています。ここでτ アプリでV スリップの直線的な増加が発見されました。これは、アラルらの観察と一致しています。また、調査ガラスビーズ懸濁液の縁に流れ場の可視化を使用して、V スリップを決定25。 セスら。負荷応力とすべり速度のスケーリングが柔らかいpartic間の相互作用によって制御されていることを示していますレ彼らは彼らの研究や壁に使用されます。壁への粒子の具体的な付着がない場合のために、彼らはまた、V スリップ及びストレスが、二次スケーリングが弱く壁28、29、30に付着した粒子のために発見されたとの間の線形関係を見つけます。 V *〜γのY 2（G：柔らかい粒子ペーストの研究はまた、降伏応力と弾性流体モデルにおける特性すべり速度V *は独立して決定することができる物理的流体と粒子パラメータからV *を計算することを可能にする29を提示される明らかにする0 R /η 秒 ）（G P / G 0）1/3。この特性すべり速度は、Yと弾性率G 0、溶媒粘度ηS、ならびにparticlγ歪みを生じるペーストに依存しますE半径R及び弾性率G P。この単純な推定値（VのA * = 375ミクロン秒-1およびV B * = 118ミクロン秒-1）から得られた値は、大きさのオーダーに対して（ 図9）だけでなく、実験結果と非常によく一致してもペーストAとBとの間の差についてサンプルのこぼれは、各ペーストのための臨界回転速度特性で、ここで観察されます。こぼれは、純粋な車では発生しません。この現象は、ペーストのレオロジー特性評価を制限し、また、特定の処理又はコーティング動作のために関連し得るが、その物理的起源は依然として未解決のままです。 ビデオ録画は、さらにその壁スリップ、プラグフローを示し、サンプル流出は振動剪断試験中に除外することができます。したがって、剪断弾性率の低下や上昇はSmaIで3段振動せん断試験の間に観察さステージIおよびIIIにおけるL振動振幅ならびに大変形振幅<img alt="方程式" src="/files/ftp_upload/55377/55377eq2.jpg" /> &gt; <img alt="方程式" src="/files/ftp_upload/55377/55377eq2.jpg" /> Cは、直接、構造ブレークダウンし、回復に起因することができます。飽和するまでステージIIにおける増加変形振幅の振動剪断増加中不可逆的な構造変化の度合いは、振幅掃引試験におけるGのクロスオーバー」およびG 『』に対応する変形に達したことを示したが、不可逆的な損傷することができステージIIにおける高振幅せん断の持続時間とは無関係です。段階IIの大きなせん断変形に対して弾性率の変化、ひいてはサンプル構造が10以上4秒の時間を待った後ので、ここで不可逆的と呼ばれ、貯蔵弾性率は、その初期値（データは示していない）よりもはるかに低いです。 図15に示すデータは、待ち時間に制限されています明瞭のために1500秒の時間。しかし、印刷工程の時間スケールでも、以下の秒のオーダーであることに留意すべきです。これは、本研究で用いた従来の回転式レオメーターのセットアップとアクセスできません。 本研究で用いたギャップの高さはまた、現代の印刷エレクトロニクスのスクリーン印刷における典型的なメッシュ開口よりはるかに大きいです。プレートプレートジオメトリを使用して、レオロジー測定は、典型的には、レオロジー測定に使用される大型のプレートのための機械的調整の限界に起因するような小さなギャップ開口部で行うことができません。さらに、大きなギャップ分離は、リムに試料変形の可視化を容易にするためにここで選択されています。 キャピラリー分裂伸長レオメーター、引張試験機を用いて試験を延伸フィラメントは伸長フローの高度に充填されたペーストの変形および分裂挙動を特徴付けるために使用することができます。破断伸び、そしてm伸長時aximum力は、これらの試験から得られるパラメータであり、スクリーン印刷時にスキージスナップオフに関連し得ます。 最後に、有意差は、本研究で調べた2種類の市販銀ペーストに関して上述したすべての実験で観察されました。それらの性能のためのレオロジーペースト特性の関連性の拡張議論は異なるペーストおよび車両の幅広いさまざまなデータに基づいて後続の用紙に対処します。

シリコン太陽電池の前面金属化は、一般的に従来のスクリーン印刷を用いて実現されます。ステンシル印刷、インクジェット印刷及びフレキソ印刷1以外に、スクリーン印刷は、多くの印刷アプリケーション2のために1970年代から使用されてきました。これは、汎用性の高い技術であり、太陽電池の生産では、低印刷コストでシンプルかつ高速なメタライゼーションを保証します。しかし、スクリーン印刷ペーストの流動特性は慎重に邪魔されず、欠陥のない処理を保証するために調整しなければなりません。狭い均一なラインパターンが達成されなければならないので、これは、太陽電池の金属化において特に困難です。また、ペーストレシピを注意深く高密度銀粒子、相分離および粒子凝集の沈降を回避するために調整されなければなりません。 太陽電池の前面側のメタライゼーションのための高度に濃縮された導電性スクリーン印刷ペーストmainlyが三の成分3、4、5、6から成る導電性材料、良好な電気伝導度7,8を設ける一般ミクロンサイズの銀粒子。特にペーストが狭いスクリーンメッシュを通過することを可能にする連続相、いわゆる車両、また、流動性を調整するための添加剤を含む基材に粒子の濡れ、膜形成および接着を促進する有機バインダ、溶剤および添加剤の混合物、簡単;無機バインダー（ガラス粉末）を接着促進剤として作用し、低温での焼結プロセスを起動します。 高アスペクト比の微細な線を印刷すると、高い降伏応力と発音ずり減粘の挙動9を示す銀ペーストを必要とします。高い降伏応力が良いSHAPを保証しますペーストは、ペーストは10 3秒を超えであると推定された高剪断速度に曝される狭いメッシュ開口部を通って流れるときに電子精度と高剪断速度での強力なずり減粘一方、高アスペクト比と対応して低い粘度が必要である-1 10。 印刷プロセスの間に、ペーストは非常に異なった変形率及び応力にさらされています。まず、ペーストをスクリーン上に載っています。次いで、スキージ作用及びペーストを基板上にスクリーンの開口を貫通します。シリコンウエハ上のペーストを塗布した後、構造及び粘度は、基板上に広がるペーストを禁止するために迅速に回復しなければなりません。これは、より高いシェーディング損失10、11、12、13、14、15、太陽電池性能を低下させます。印刷されたフィンガーラインの中断、いわゆるmeshmarksは、ペーストのレオロジーに応じてメッシュ配線の交点に発生する可能性があります。 meshmarksを平準化のための時間が必要な限りでなく、16可能な限り低く広がり指のラインを維持するのに十分短くする必要があります。 基板上にメッシュを通って流れるようにペーストするために必要なスキージ圧力は、良好な形状精度3、6、9、17、18を提供するのに必要な高い降伏応力に注意深く調整しなければなりません。粒子が密に充填され、強く相互作用して複雑な構造を形成します。したがって、降伏応力、剪断減粘性およびチキソトロピー以外に、剪断バンディング又は雪崩のような様々な他の複雑な流れ現象は、懸濁液19で発生することがあり、20 &lt;/ SUP&gt;、21。ウォールスリップは、濃縮懸濁液22、23、24、25にも非常に重要です。低粘度の液体の薄層、層が枯渇または粒子を含まない、すなわち 、次の壁25に形成された26、27、28、29、30、31及び狭い間隙またはチャネルを通る流れを制御することができるされています。 そうスクリーン印刷ペーストの包括的なレオロジー特徴付けは、加工性および製品の機能を向上させるために不可欠です。本研究では、2種類の市販銀ペーストを特徴としています。これらのペーストは、実質的に異なる印刷性能を発揮します。レオロジーCHARそのような材料のacterizationは非常に厳しいです。回転レオメーターを使用して、定常剪断粘度のも簡単な決意起因壁スリップ、栓流、剪断バンディング及びペースト流出の主要な課題です。したがって、以前の研究は、上記の現象が生じにくいれるインク3、6、15、いわゆる、振動剪断測定値10、17、21または低濃度の銀ペーストの特性に焦点を当てました。 濃厚銀ペーストの流動挙動の堅牢かつ有意義な特性評価のためのプロトコルは、ビデオ録画の助けを借りて定義することができます。平行平板試料固定具を有する回転剪断レオメータを明確プラグフロー、壁スリップ、及び剪断バンディングが粗いプレートに依存することを実証し、本研究で使用されています非自明な方法でネス。 以前の研究では、濃縮された懸濁液の安定した捩り流れの壁スリップの時間依存開発が異なるプレート粗さを調べました。ポリマーバインダ溶液中の固体のガラス球の高度に濃縮された懸濁液の流れを可視化し、増加したプレートまたは内筒粗さは、壁のスリップを防止しました。しかし、プレートの粗さを大きくすると、サンプル22、25の破断が生じました。壁の粗さが増加した際に骨折が小さい見かけのせん断速度で起こりました。剪断応力は降伏応力τyを25よりも小さいτにおける粗面の凹凸の先端が破壊を開始する、板面に応力集中点として作用するかもしれません。 ウォールスリップが高濃縮ペーストのスクリーン印刷のパフォーマンスのために重要であると考えられています。過去<html> eは高い壁スリップで簡単にメッシュを通して滑ると、基板上の堆積物が大幅に32に増加されます。ビデオ録画の助けを借りて、壁のスリップが直接異なる実験のプロトコルのために観察することができます。スリップ速度が低い粗さを有する滑らかなプレートを使用して回転板の角速度から直接決定することができます。しかし、銀ペーストのフロー挙動決意は固有の制限があります。懸濁液は不透明なので、オプティカルフロー場観測のみ試料縁に行うことが可能です。以前の研究では、同時にサンプル内壁面スリップや変形を決定することを試みました。彼らは降伏応力下の滑りを観察し、せん断応力のすべり速度の二次依存を発見しました。透明粘土懸濁液の流動挙動は、バルク材料に注入染料顔料線の変形以下ピニョン27により調べました。 Persello ら。XREF &quot;&gt; 26が濃厚水性シリカ懸濁液を調べた。彼らは、壁スリップを抑制するために、プレートの粗さを増加させると均一な試料変形を生じるが、バルク破壊を引き起こした。集中されているソフトミクロゲル粒子、濃縮エマルジョンのペーストスリップと試料変形しないことがわかっ論文28、29、30、31の直列に議論した。蛍光トレーサー粒子はコーンプレートジオメトリーにおけるこれらの透明試料内の流れ場を決定するために使用された。これらは、それぞれの降伏応力における特性すべり速度V *を発見材料及びτyを以下の剪断応力τとのすべり速度の増加のためのべき乗則一の指数は、非付着粒子と粒子と壁との間の弱い引力の場合に2つのために発見されました。 研究では、彼女を発表E変形の開発及び制御応力及び制御された剪断速度条件下で流れが監視されます。リファレンス25で報告された調査結果とは対照的に、増加プレートの粗さは、両方の調査ペーストのための骨折にはなりません。また、壁のスリップ及びプラグフローは、プレートの粗さを増加させることによってだけ抑制することができません。これらの現象は、粒子サイズ及びプレートの凹凸の比率によって制御されるように見えます。おそらくレオメータプレートに遠心に作用する力と摩擦力とのバランスによって決定される特性回転速度でのサンプル流出セット。しかし、粘度決意が可能な剪断速度範囲を決定することができると同時に、壁のスリップを定量化することができます。また、キャピラリーレオメーターは、印刷処理に関連するより高い剪断速度での粘度を決定するために使用されます。 定常剪断レオメトリーの困難にもかかわらず、明確に定義された振動剪断変形C容易に実現すること。三段振動試験（一定周波数、異なる振動振幅）がスクリーン印刷プロセス10をシミュレートし、ペーストの構造の回復を検討することができます。 最初の「プレプリント」ステップにおいて、小さい変形は、安静時の弾性と粘性特性を決定するために適用されます。第二の「印刷」ステップは、ブレードコーティング及びペースト構造を破壊する十分に高い変形振幅を適用することにより、スクリーンメッシュを通過するペーストをシミュレートします。最終的な「印刷後」ステップにおいて、小さな変形は、ペーストの構造回復を検出するために適用されます。初期モジュラス値は広がりますがmeshmarksを避けるには余りにも速くないペーストを避けるために迅速に到達する必要があります。ここで紹介する調査は、以前に周21によって報告された構造回復が不完全であることを確認してください。周は構造変化が生じていることを示すことができましたエチルセルロース溶液に懸濁した銀粒子を用いたデカップリングフィラーマトリックスの充填剤クラスターの破壊による。本研究ではビデオ録画を観察不可逆的構造変化が壁スリップ、剪断バンディング、プラグ流又は試料流出の発生に関連するアーチファクトではないことを明らかにする。また、構造破壊の程度が強く第二段階において適用変形の振幅に依存するが、ほとんど適用されるひずみの時間間隔に依存することが見出されています。この局面は、周の実験では認識されませんでした。構造破壊や回復のペースト組成物の影響は、その後の論文で説明します。 最後に、画面のスナップオフ時のペーストの挙動をシミュレートする方法が提示されています。キャピラリー分裂伸長レオメーターおよび商業引張試験機は、関数として延伸中にペーストが破壊れる延伸比と最大軸力を決定するために使用されます伸長速度の。 ビデオ録画は、平行平板型回転レオメトリーを用いて、銀ペーストの意味のレオロジー特性決定のために必要な適切な測定プロトコルを見つけるために不可欠であることが判明しています。ビデオデータは、物理的に明確に定義された降伏応力及び粘度値を決定することができた剪断速度と剪断応力レジームの決意を可能にしました。プレートの粗さとプレートの分離パラメータの適切な選択は、また、これらのビデオ録画に基づいていました。壁スリップ、純粋な栓流、剪断バンディング又は試料流出が発生するための実験の設定が明確に同定することができました。ここでの調査ペーストは、太陽電池の前面側メタライゼーションのために使用されています。しかしながら、注意深いビデオレオロジー特性評価も高い密度、ミクロンサイズの粒子を含む濃縮された懸濁液の様々な他の種類のために重要であるサポート。

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>endoscopy</td>
			<td>Visitool</td>
			<td>TVS80.280.BF6.AD10.2</td>
			<td>full name: TV-Endoskop, C-Mount, Variookular 2X, &#216; 8mm x ca. 280mm, 0&#176;, BF:6mm, AD 10mm</td>
		</tr>
		<tr>
			<td>commercial silver paste&#160;</td>
			<td>Heraeus Deutschland GmbH &#38; Co. KG 
			Global Business Unit Heraeus Photovoltaics</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>rheometer A</td>
			<td>Anton Paar</td>
			<td>Physica MCR 501</td>
			<td>Rq = 2 - 4 &#181;m</td>
		</tr>
		<tr>
			<td>rheometer B</td>
			<td>Thermo Scientific</td>
			<td>Haake Mars II</td>
			<td>Rq = 1.15 &#181;m 
			Rq = 9 &#181;m</td>
		</tr>
		<tr>
			<td>rheometer C</td>
			<td>Thermo Scientific (formerly Haake GmbH)</td>
			<td>Rheostress 150</td>
			<td>vane geometry</td>
		</tr>
		<tr>
			<td>sandpaper</td>
			<td>Jean Wirtz D&#252;sseldorf Metallographie</td>
			<td>P320 C</td>
			<td>Rq = 9 &#181;m 
			grain size = 46.2 &#177; 1.5</td>
		</tr>
		<tr>
			<td>recording software</td>
			<td>Debut Video Capture</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>LED Spotlight</td>
			<td>Kaleep&#160;</td>
			<td>48W Led Work Lights 
			Offroads Lights 
			Lamp Spotlight Floodlight&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>capillary breakup elongational rheometer</td>
			<td>Thermo Scientific (Haake)</td>
			<td>HAAKE CaBER1</td>
			<td></td>
		</tr>
		<tr>
			<td>tensile tester</td>
			<td>Stable Micro Systems, Godalming, UK</td>
			<td>TA.XT plus 
			Texture Analyzer&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>50 N load cell</td>
			<td>Stable Micro Systems, Godalming, UK</td>
			<td>Serialnumber: 10256249</td>
			<td></td>
		</tr>
		<tr>
			<td>a modified capillary rheometer</td>
			<td>G&#246;ttfert Rheograph 2000 (G&#246;ttfert Werkstoff-Pr&#252;fmaschinen GmbH, Buchen Germany)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>500 bar pressure transducer</td>
			<td>Gefran, Selingenstadt, Germany</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

challenges in rheological characterization of highly concentrated suspensions &#8212; a case study for screen-printing silver pastes

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the manifold requirements during processing and application of such complex fluids. In this investigation, measuring protocols for a conclusive assessment of different process relevant rheological parameters have been evaluated. This includes the determination of yield stress, viscosity, wall slip velocity, structural recovery after large deformation and elongation at break as well as tensile force during filament stretching.
The importance of concomitant video recordings during parallel-plate rotational rheometry for a significant determination of rheological quantities is demonstrated. The deformation profile and flow field at the sample edge can be determined using appropriate markers. Thus, measurement parameter settings and plate roughness values can be identified for which yield stress and viscosity measurements are possible. Slip velocity can be measured directly and measuring conditions at which plug flow, shear banding or sample spillover occur can be identified clearly. 
Video recordings further confirm that the change in shear moduli observed during three stage oscillatory shear tests with small deformation amplitude in stage I and III but large oscillation amplitude in stage II can be directly attributed to structural break down and recovery. For the pastes investigated here, the degree of irreversible, shear-induced structural change increases with increasing deformation amplitude in stage II until a saturation is reached at deformations corresponding to the crossover of G' and G'', but the irreversible damage is independent of the duration of large amplitude shear. 
A capillary breakup elongational rheometer and a tensile tester have been used to characterize deformation and breakup behavior of highly filled pastes in uniaxial elongation. Significant differences were observed in all experiments described above for two commercial screen-printing silver pastes used for front side metallization of Si-solar cells.

Watch this Scientific Journal Video about Challenges in Rheological Characterization of Highly Concentrated Suspensions Ã¢â‚¬â€ A Case Study for Screen-printing Silver Pastes at JoVE.com

Challenges in Rheological Characterization of Highly Concentrated Suspensions &#8212; A Case Study for Screen-printing Silver Pastes

A protocol for a robust and application relevant rheological characterization of highly concentrated suspensions is presented. Silver pastes used for screen-printing application in solar cell production are employed as model systems.

高度に濃縮された懸濁液のレオロジー特性評価における課題 - スクリーン印刷シルバーペーストのためのケーススタディ

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the ...

challenges-rheological-characterization-highly-concentrated

Research

JoVE Journal

Engineering

19.8K ビュー.  Karlsruhe Institute of Technology. A protocol for a robust and application relevant rheological characterization of highly concentrated suspensions is presented. Silver pastes used for screen-printing application in solar cell production are employed as model systems. 

ビデオ: Challenges in Rheological Characterization of Highly Concentrated Suspensions — A Case Study for Screen-printing Silver Pastes

A Method to Fabricate Disconnected Silver Nanostructures in 3D

The standard nanofabrication toolkit includes techniques primarily aimed at creating 2D patterns in dielectric media. Creating metal patterns on a submicron scale requires a combination of nanofabrication tools and several material processing steps. For example, steps to create planar metal structures using ultraviolet photolithography and electron-beam lithography can include sample exposure, sample development, metal deposition, and metal liftoff. To create 3D metal structures, the sequence is repeated multiple times. The complexity and difficulty of stacking and aligning multiple layers limits practical implementations of 3D metal structuring using standard nanofabrication tools. Femtosecond-laser direct-writing has emerged as a pre-eminent technique for 3D nanofabrication.1,2 Femtosecond lasers are frequently used to create 3D patterns in polymers and glasses.3-7 However, 3D metal direct-writing remains a challenge. Here, we describe a method to fabricate silver nanostructures embedded inside a polymer matrix using a femtosecond laser centered at 800 nm. The method enables the fabrication of patterns not feasible using other techniques, such as 3D arrays of disconnected silver voxels.8 Disconnected 3D metal patterns are useful for metamaterials where unit cells are not in contact with each other,9 such as coupled metal dot10,11or coupled metal rod12,13 resonators. Potential applications include negative index metamaterials, invisibility cloaks, and perfect lenses.
In femtosecond-laser direct-writing, the laser wavelength is chosen such that photons are not linearly absorbed in the target medium. When the laser pulse duration is compressed to the femtosecond time scale and the radiation is tightly focused inside the target, the extremely high intensity induces nonlinear absorption. Multiple photons are absorbed simultaneously to cause electronic transitions that lead to material modification within the focused region. Using this approach, one can form structures in the bulk of a material rather than on its surface.
Most work on 3D direct metal writing has focused on creating self-supported metal structures.14-16 The method described here yields sub-micrometer silver structures that do not need to be self-supported because they are embedded inside a matrix. A doped polymer matrix is prepared using a mixture of silver nitrate (AgNO3), polyvinylpyrrolidone (PVP) and water (H2O). Samples are then patterned by irradiation with an 11-MHz femtosecond laser producing 50-fs pulses. During irradiation, photoreduction of silver ions is induced through nonlinear absorption, creating an aggregate of silver nanoparticles in the focal region. Using this approach we create silver patterns embedded in a doped PVP matrix. Adding 3D translation of the sample extends the patterning to three dimensions.

Femtosecond-laser direct-writing is frequently used to create three-dimensional (3D) patterns in polymers and glasses. However, patterning metals in 3D remains a challenge. We describe a method for fabricating silver nanostructures embedded inside a polymer matrix using a femtosecond laser centered at 800 nm.

3Dで切断された銀ナノ構造体を製造する方法

The standard nanofabrication toolkit includes  techniques primarily aimed at creating 2D patterns in dielectric media. Creating  metal patterns on a ...

工学

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information support1,2,3. In this context, metal nanowires are especially desirable for realizing dense routing networks4. A prerequisite to operate such shared nanowire-based platform relies on our ability to electrically contact individual metal nanowires and efficiently excite surface plasmon polaritons5 in this information support. In this article, we describe a protocol to bring electrical terminals to chemically-synthesized silver nanowires6 randomly distributed on a glass substrate7. The positions of the nanowire ends with respect to predefined landmarks are precisely located using standard optical transmission microscopy before encapsulation in an electron-sensitive resist. Trenches representing the electrode layout are subsequently designed by electron-beam lithography. Metal electrodes are then fabricated by thermally evaporating a Cr/Au layer followed by a chemical lift-off. The contacted silver nanowires are finally transferred to a leakage radiation microscope for surface plasmon excitation and characterization8,9. Surface plasmons are launched in the nanowires by focusing a near infrared laser beam on a diffraction-limited spot overlapping one nanowire extremity5,9. For sufficiently large nanowires, the surface plasmon mode leaks into the glass substrate9,10. This leakage radiation is readily detected, imaged, and analyzed in the different conjugate planes in leakage radiation microscopy9,11. The electrical terminals do not affect the plasmon propagation. However, a current-induced morphological deterioration of the nanowire drastically degrades the flow of surface plasmons. The combination of surface plasmon leakage radiation microscopy with a simultaneous analysis of the nanowire electrical transport characteristics reveals the intrinsic limitations of such plasmonic circuitry.

Silver nanowires can simultaneously transport electrons and optical information in the form of surface plasmons. A procedure is described here to realize such a shared circuitry and the limitations at propagating both information carriers are evaluated.

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information ...

Fabrication of High Contrast Gratings for the Spectrum Splitting Dispersive Element in a Concentrated Photovoltaic System

High contrast gratings are designed and fabricated and its application is proposed in a parallel spectrum splitting dispersive element that can improve the solar conversion efficiency of a concentrated photovoltaic system. The proposed system will also lower the solar cell cost in the concentrated photovoltaic system by replacing the expensive tandem solar cells with the cost-effective single junction solar cells. The structures and the parameters of high contrast gratings for the dispersive elements were numerically optimized. The large-area fabrication of high contrast gratings was experimentally demonstrated using nanoimprint lithography and dry etching. The quality of grating material and the performance of the fabricated device were both experimentally characterized. By analyzing the measurement results, the possible side effects from the fabrication processes are discussed and several methods that have the potential to improve the fabrication processes are proposed, which can help to increase the optical efficiency of the fabricated devices.

The fabrication of high contrast gratings as the parallel spectrum splitting dispersive element in a concentrated photovoltaic system is demonstrated. Fabrication processes including nanoimprint lithography, TiO2 sputtering and reactive ion etching are described. Reflectance measurement results are used to characterize the optical performance.

集中太陽光発電システムにおけるスペクトル分割分散素子の高コントラスト回折格子の作製

High contrast gratings are designed and fabricated and its application is proposed in a parallel spectrum splitting dispersive element that can improve ...

Integration of Light Trapping Silver Nanostructures in Hydrogenated Microcrystalline Silicon Solar Cells by Transfer Printing

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly known as plasmonic effects, play an important role. Research in this field has, however, been impeded owing to the difficulty of fabricating devices containing the desired functional metal nanostructures. In order to provide a viable strategy to this issue, we herein show a transfer printing-based approach that allows the quick and low-cost integration of designed metal nanostructures with a variety of device architectures, including solar cells. Nanopillar poly(dimethylsiloxane) (PDMS) stamps were fabricated from a commercially available nanohole plastic film as a master mold. On this nanopatterned PDMS stamps, Ag films were deposited, which were then transfer-printed onto block copolymer (binding layer)-coated hydrogenated microcrystalline Si (&#181;c-Si:H) surface to afford ordered Ag nanodisk structures. It was confirmed that the resulting Ag nanodisk-incorporated &#181;c-Si:H solar cells show higher performances compared to a cell without the transfer-printed Ag nanodisks, thanks to plasmonic light trapping effect derived from the Ag nanodisks. Because of the simplicity and versatility, further device application would also be feasible thorough this approach.

A viable transfer printing-based methodology to introduce plasmonic metal nanostructures in solar cells is described. Using nanopillar poly(dimethylsiloxane) stamps, an Ag-based ordered nanodisk array was integrated with standard hydrogenated microcrystalline Si solar cells, which led to improved device performances due to plasmonic light trapping.

転写印刷により水素化微結晶シリコン太陽電池の光トラッピング銀ナノ構造の統合

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly ...

A Fabrication Method for Highly Stretchable Conductors with Silver Nanowires

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of stretchable electronic devices is the preparation of stretchable conductors with great mechanical stability. In this study, we developed a simple fabrication method to chemically solder the contact points between silver nanowire (AgNW) networks. AgNW nanomesh was first deposited on a glass slide via spray coating method. A reactive ink composed of silver nanoparticle (AgNPs) precursors was applied over the spray coated AgNW thin films. After heating for 40 min, AgNPs were preferentially generated over the nanowire junctions to solder the AgNW nanomesh, and reinforced the conducting network. The chemically modified AgNW thin film was then transferred to polyurethane (PU) substrates by casting method. The soldered AgNW thin films on PU exhibited no obvious change in electrical conductivity under stretching or rolling process with elongation strains up to 120%.

A simple synthesis method is used to chemically solder silver nanowire thin film to fabricate highly stretchable and conductive metal conductors.

シルバーナノワイヤーと伸縮性の高い導体の製造方法

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of ...

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic recording of image sequences. The basic components, features, constraints and optimization tips of a 3D-PTV topology consisting of a high-speed camera with a four-view splitter are described and discussed in this article. The technique is applied to the intermediate flow field (5 &#60;x/d &#60;25) of a circular jet at Re &#8776; 7,000. Lagrangian flow features and turbulence quantities in an Eulerian frame are estimated around ten diameters downstream of the jet origin and at various radial distances from the jet core. Lagrangian properties include trajectory, velocity and acceleration of selected particles as well as curvature of the flow path, which are obtained from the Frenet-Serret equation. Estimation of the 3D velocity and turbulence fields around the jet core axis at a cross-plane located at ten diameters downstream of the jet is compared with literature, and the power spectrum of the large-scale streamwise velocity motions is obtained at various radial distances from the jet core.

A three-dimensional particle tracking velocimetry (3D-PTV) system based on a high-speed camera with a four-view splitter is described here. The technique is applied to a jet flow from a circular pipe in the vicinity of ten diameters downstream at Reynolds number Re &#8776; 7,000.

ジェット流の場合：乱流のアプリケーションのための3次元粒子追跡流速

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

のための新しい方法<em&gt;現場で</em&gt;ナノスケール試料の電気機械的特性

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for Cu(In,Ga)Se2 Solar Cells

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction of degradation mechanisms and prevention of module field failure can consequently decrease investment risks as well as increase the electricity yield. An improved knowledge level can for these reasons significantly decrease the total costs of PV electricity. 
In order to better understand and minimize the degradation of PV modules, the occurring degradation mechanisms and conditions should be identified. This should preferably happen under combined stresses, since modules in the field are also simultaneously exposed to multiple stress factors. Therefore, two 'Combined Stress test with in situ measurement' setups have been designed and constructed. These setups allow the simultaneous use of humidity, temperature, illumination, and electrical biases as independently controlled stress factors on solar cells and minimodules. The setups also allow real-time monitoring of the electrical properties of these samples. This protocol presents these setups and describes the experimental possibilities. Moreover, results obtained with these setups are also presented: various examples about the influence of both deposition and degradation conditions on the stability of thin film Cu(In,Ga)Se2 (CIGS) as well as Cu2ZnSnSe4 (CZTS) solar cells are described. Results on the temperature dependency of CIGS solar cells are also presented.

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for CuIn,GaSe2 Solar Cells

Two &#39;Combined Stress test with in situ measurement&#39; setups, which allow real-time monitoring of accelerated degradation of solar cells and modules, were designed and constructed. These setups allow the simultaneous use of humidity, temperature, electrical biases, and illumination as independently controlled stress factors. The setups and various experiments executed are presented.

その場で太陽電池とモジュールの加速劣化のモニタリング: Cu (In, Ga) Se2太陽電池に関するケーススタディ

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction ...

Fabrication of Ultra-thin Color Films with Highly Absorbing Media Using Oblique Angle Deposition

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present an advanced method for fabricating ultra-thin color films with improved characteristics. The proposed process addresses several fabrication issues, including large area processing. Specifically, the protocol describes a process for fabricating ultra-thin color films using an electron beam evaporator for oblique angle deposition of germanium (Ge) and gold (Au) on silicon (Si) substrates.&#160; Film porosity produced by the oblique angle deposition induces color changes in the ultra-thin film. The degree of color change depends on factors such as deposition angle and film thickness. Fabricated samples of the ultra-thin color films showed improved color tunability and color purity. In addition, the measured reflectance of the fabricated samples was converted into chromatic values and analyzed in terms of color. Our ultra-thin film fabricating method is expected to be used for various ultra-thin film applications such as flexible color electrodes, thin film solar cells, and optical filters. Also, the process developed here for analyzing the color of the fabricated samples is broadly useful for studying various color structures.

We present a detailed method for fabricating ultra-thin color films with improved characteristics for optical coatings. The oblique angle deposition technique using an electron beam evaporator allows improved color tunability and purity. Fabricated films of Ge and Au on Si substrates were analyzed by reflectance measurements and color information conversion.

斜め蒸着を使用してメディアを高吸収極薄カラー フィルムの作製

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present ...

Conducting Elevated Temperature Normal and Combined Pressure-Shear Plate Impact Experiments Via a Breech-end Sabot Heater System

A novel approach for conducting normal and/or combined pressure-shear plate impact experiments at test temperatures up to 1000 &#176;C is presented. The method enables elevated temperature plate-impact experiments aimed towards probing dynamic behavior of materials under thermomechanical extremes, while mitigating several special experimental challenges faced while performing similar experiments using the conventional plate impact approach. Custom adaptations are made to the breech-end of a single-stage gas-gun at Case Western Reserve University; these adaptations include a precision-machined extension piece made from SAE 4340 steel, which is strategically designed to mate the existing gun-barrel while providing a high tolerance match to the bore and keyway. The extension piece contains a vertical cylindrical heater-well, which houses a heater assembly. A resistive coil heater-head, capable of reaching temperatures of up 1200 &#176;C, is attached to a vertical stem with axial/rotational degrees of freedoms; this enables thin metal specimens held at the front-end of a heat-resistant sabot to be heated uniformly across the diameter to the desired test temperatures. By heating the flyer plate (in this case, the sample) at the breech-end of the gun-barrel instead of at the target-end, several critical experimental challenges can be averted. These include: 1) severe changes in the alignment of the target plate during heating due to the thermal expansion of the several constituents of the target holder assembly; 2) challenges that arise due to the diagnostics elements, (i.e., polymer holographic gratings, and optical probes) being too close to the heated target assembly; 3) challenges that arise for target plates with an optical window, where crucial tolerances between the sample, bond layer, and window become increasingly difficult to maintain at high temperatures; 4) in the case of combined compression-shear plate impact experiments, the need for high-temperature resistant diffraction gratings for the measurement of transverse particle velocity at the free surface of the target; and 5) limitations imposed on the impact velocity necessary for unambiguous interpretation of the measured free surface velocity versus time profile due to thermal softening and possibly yielding of the bounding target plates.By utilizing the adaptations mentioned above, we present results from a series of reverse geometry normal plate impact experiments on commercial purity aluminum at a range of sample temperatures. These experiments show decreasing particle velocities in the impacted state, which are indicative of material softening (decrease in post-yield flow stress) with increasing sample temperatures.

Here, we present a detailed protocol of a new approach for conducting elevated temperature reverse normal plate impact, and combined pressure-and-shear plate impact. The approach involves the use of a breech-end resistive coil heater to heat a sample held at the front-end of a heat-resistant sabot to the desired temperature.

通常の温度の上昇を実施し、尾端サボ ヒーター システムを介して圧力剪断平板衝突試験を組み合わせる

A novel approach for conducting normal and/or combined pressure-shear plate impact experiments at test temperatures up to 1000 &#176;C is presented. The ...