The long-standing collaboration with Chang-Beom Eom at the University of Wisconsin-Madison, who provided the LAO/STO samples, is gratefully acknowledged. Video editing assistance from Christopher Solis is greatly appreciated. This work is supported by NSF (DMR-1104191, DMR-1124131), ARO (W911NF-08-1-0317), and AFOSR (FA9550-10-1-0524, FA9550-12-1-0268, FA9550-12-1-0057).

1。LAO / STOヘテロ構造を取得<ol><li> TiO 2の終端のSTO基板上にパルスレーザー堆積法により成長したLAOの3.4単位の細胞からなる酸化物ヘテロ構造を得る。試料の成長の詳細は参考文献22に記載されている。 </li></ol>サンプルの2。フォトリソグラフィー処理チップキャリアへの配線キャンバスのためのボンディングパッドと、LAO / STO界面に電気接点を作成します。個々の処理ステップを以下に詳細に説明する。 <ol><li>スピン、フォトレジスト<ol><li>次いで、30秒間4,000 rpmで、5秒間600 rpmで試料上にフォトレジストをスピン。フォトレジスト層は約2μmの厚さになります。 1分間95℃でサンプルを焼く。 </li></ol></li><li> 5 MW / cm 2のドーズ量で100秒間、320 nmの光でマスクアライナを用いてフォトレジストを公開します。 </li><li>フォトレジスト現像FOにおけるフォトレジストを開発rは1分。 </li><li>イオンミリング<ol><li>フォトレジストで覆われていない領域に15物質のナノメートル（LAOとSTO）を除去するのAr +イオンミルを使用してください。入ってくるのAr +イオンビームに対して垂直な方向に22.5°の角度でサンプルを置きます。のAr +エッチング速度が較正されていない場合は、材料の正確な量が除去されることを保証するために、キャリブレーションの実行を行う。 AFMまたは同等profilmetryを用いたエッチング深さを決定する。 </li></ol></li><li> TiとAuとのDCスパッタリング<ol><li>デポジットさ4nmのTi、次いで25nmのAuを試料上にAuが露出STO層と電気的に接触するようになっている。スパッタ圧力範囲は2-6×10 -7トルであり、スパッタリングは、RTでのサンプルで行われる。シャッターを10分間にTiをプリスパッタ100W、[開くシャッターが閉鎖され、50Wで1分間、完了すると、100Wで20秒すぐにプリスパッタ金をスパッタしてのサンプルに30秒間のAuスパッタ50 W·カリ希望のTiとAuの厚さを生成するために時間をフィブラート。 </li></ol></li><li>離昇<ol><li>サンプルの表面からフォトレジストを除去するアセトン/ IPA、超音波洗浄を使用してください。 </li></ol></li><li>第2層<ol><li>ステップ4（ すなわち 、イオンミリングを除く）を除く第二のリソグラフィプロセスは、個々のボンディングパッドに金ワイヤ接続を作成するために使用される。 2つのパターンが、彼らは電気的短絡を生じないことを保証するために十分に整列させる必要があります。 </li></ol></li><li>プラズマ洗浄。 <ol><li> IPCバレルエッチャーは、パターン溝にフォトレジスト残渣を除去するために使用される。 1分間100 Wと1トルのアルゴンで使用される機器</li></ol></li></ol> 3。ワイヤボンド書き込みのために準備するためのサンプル<ol><li> 28使用可能なピンとチップ·キャリア（ 図2A）に、LAO / STOサンプルをマウントします。 </li><li>ワイヤボンド構造</li></ol>注：電気Cを作るために、ワイヤボンダーを使用して、試料上のボンディングパッドとチップキャリアとの間のonnections。電気接点とチップキャリアとの間で1ミル（25ミクロン）金ワイヤを取り付けます。ナノ構造を書く 4。ナノ構造をお書きください。 <ol><li>導電性ナノ構造（ 図3A）の非公式スケッチを作成します。 </li><li>スケーラブルベクターグラフィックス（SVG）エディタ（ 図3B）を開きます。 <ol><li>テンプレートを使用するか、AFM像と一致するようにウィンドウのサイズを定義します。 </li><li> SVGエディタにサンプルのAFM像をロードします。 </li><li>原子間力顕微鏡の画像に重ねたナノ構造要素を作成します。 </li></ol></li><li>ナノリソグラフィプログラムにSVGファイルをロードします。 </li><li>導電性ナノ構造体を作成するために、リソグラフィ·ソフトウェアを実行します。 <ol><li>ナノ構造を消去するために、ナノ構造、およびV チップ =-10Vを作成するには、V チップ = +10 Vを使用してください。 </li><li> 20に至るまでの速度で、C-AFMの先端を移動2ミクロン/秒0ナノメートル/秒。 </li></ol></li></ol> 5。デバイスを冷却し、測定を行う<ol><li>すべての白のライトをオフにして、赤色フィルタ/光源を使用しています。 </li><li>原子間力顕微鏡システムからサンプルを抽出します。 </li><li>希釈冷凍機（A）にサンプルをロードします。 </li><li>試料が冷却される温度（B）対抵抗を測定します。 </li><li>低温（℃）で輸送特性を測定します。 </li></ol>

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The authors have nothing to disclose.

Successful creation of nanostructures depends on several critical steps. It is important that the LAO/STO samples are grown with a thickness that is known to be at the boundary between the insulating and conductive phase. (Details of sample growth fall outside the scope of this paper, but are crucial for overall success.) Second, it is important to have relative humidity within the range 25-45% for successful c-AFM writing. Values below 25% are unlikely to produce conductive nanostructures, while too high humidity will generally produce uncontrollably large features. Also, temperature control of the AFM is important if the c-AFM tip needs to achieve precise registry over long periods of time. Once the nanostructures are created, they must be placed in a vacuum environment if experiments lasting longer than a few hours are to be performed. For the experiments described here, the structure is created and within minutes transferred to a vacuum environment.
It is recommend before writing that a &#8220;writing test&#8221; be performed on all relevant electrodes. In such a test, two virtual electrodes are first created, and a single nanowire is written while simultaneously monitoring the conductance. A similar test of erasure can be performed by &#8220;cutting&#8221; the nanowire shortly afterwards. If the nanostructure is decaying rapidly, the issue is most likely due either to the interfacial contacts or the canvas itself. To distinguish between these two effects, a four-terminal measurement of the conductance should be performed, and the two-terminal conductance should be compared with the four-terminal conductance as a function of time. If the two-terminal conductance is decaying more rapidly than the four-terminal conductance, then the issue is related to the electrical contacts to the interface. If the four-terminal conductance is decaying at a comparable rate, then most likely the canvas is not suitable and should be replaced.
There are natural limitations of the current method for creating nanostructures. Specifically, the writing speed for the smallest devices is limited to a few hundred nanometers per second. Speeds far above that value lead to unpredictable results. Use of parallel writing techniques are possible27,28, but are not highly developed and have their own drawbacks. The size of nanostructures that can be created is naturally limited by the scan range of the AFM being used. A high-quality AFM with closed-loop feedback in the two scan directions is highly recommended. Tracking of point-like objects on the sample surface should be performed to monitor temporal drift of the sample.
Once creation of conductive nanostructures at oxide interfaces has been mastered, there are a wide range of experimental directions that can be explored. Using this technique, a wide variety of nanostructures and devices have already been demonstrated, including nanowires18, tunnel barriers29, rectifying junctions30, field-effect transistors18, single-electron transistors31, superconducting nanowires32, nanoscale optical detectors33, and nanoscale THz emitters and detectors34.

酸化物ヘテロ構造1-5は、両方の科学的に興味深いとアプリケーション4に潜在的に有用である創発物理現象が顕著多種多様性を示す。特に、ランタンアルミ3（LAO）とのSrTiO 3（STO）6との間のインターフェースは、絶縁導電性、7超伝導、強誘電体のような8、9および強磁性挙動を示すことができる。 2006年には、ティールら LAO層の厚さは4単位セル（4uc）の臨界厚さが増加するように鋭利な絶縁体-金属転移が存在することを示した10。それは、その後3uc-LAO/STO構造は導電性の原子間力顕微鏡（C-AFM）プローブ11を局所的に制御することができるヒステリシス転移を示すことが示された。 このようにLaAlO 3 /たSrTiO 3のような酸化物界面の特性は、導電性の有無に依存する界面で電子が。これらの電子は、ゲート10バック、トップゲート電極12,13を用いて制御することができ、表面14は、強誘電体層15,16およびc-AFMリソグラフィー11を吸着。のc-AFMリソグラフィーのユニークな特徴は、非常に小さいナノスケールの特徴を作成することができることである。 二次元閉じ込めと組み合わせた電気頂ゲーティングは、多くの場合、III-V族半導体量子ドット17を作成するために使用される。代替的に、準一次元半導体ナノワイヤーは、電気的近接によってゲート制御することができる。これらの構造体を製造するための方法は、時間がかかり、一般に不可逆である。対照的に、C-AFMリソグラフィー技術は、ナノ構造は、一つの実験のために作成し、次いで（ホワイトボードと同様に）「消去」することができるという意味で、可逆的である。消去しながら、一般的には、C-AFMの書き込みは、AFMチップに印加される正の電圧を用いて行われる負電圧を用いて行われる。特定の構造を作成するために必要な時間は、デバイスの複雑さに依存するが、通常30分未満であり;そのほとんどの時間を過ごしたキャンバスを消去する。典型的な空間分解能は約10ナノメートルであるが、適切なチューニングを2ナノメートルは18作成できる限り小さくしています。 ナノスケールの製造手順の詳細は以下の通りである。ここで提供される詳細は、同様の実験が興味の研究者が行うことを可能にするのに十分であるべきである。ここで説明する方法は、半導体内の電子のナノ構造を作成するために使用される従来のリソグラフィの手法に比べて多くの利点を有する。 ここで説明するC-AFMリソグラフィー法は、走査型陽極酸化19、ディップペンナノリソグラフィー20、圧電パターニングを含む走査プローブベースのリソグラフィの努力、はるかに広いクラスの一部である21など。新規な酸化物界面を用いて結合されたここに記載のc-AFM技術は、物理的性質の前例のない様々な最高精度の電子構造のいくつかを生成することができる。

<table border="0" cellpadding="0" cellspacing="0" width="889">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:165px;">Name</td>
			<td style="width:169px;">Company</td>
			<td style="width:108px;">Catalog Number</td>
			<td style="width:447px;">Comments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Contact Aligner</td>
			<td>Karl-Suss</td>
			<td>MA6</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Spinner</td>
			<td>Solitec</td>
			<td>5110C</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ion Mill</td>
			<td>Commonwealth Scientific</td>
			<td>8C</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sputtering System</td>
			<td>Leybold-Heraeus</td>
			<td>Z-650</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Barrel Etcher</td>
			<td>Branson/IPC</td>
			<td>3000C</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Wire Bonder</td>
			<td>Westbond</td>
			<td>7700E</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">AFM</td>
			<td>Asylum Research</td>
			<td>MFP-3D</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dilution Refrigerator</td>
			<td>Quantum Design</td>
			<td>P850</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ultrasonic Wash Machine</td>
			<td>Fisher Scientific</td>
			<td>15-335-6</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Current Amplifier</td>
			<td>Femto</td>
			<td>DLPCA-200</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">LaAlO3/SrTiO3</td>
			<td>Prof. Chang-Beom Eom</td>
			<td>N/A</td>
			<td>5mm x 1mm with ~3.4 unit cells of LAO (See Reference 18)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Photoresist</td>
			<td>AZ Electronic Materials</td>
			<td>P4210</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Developer</td>
			<td>AZ Electronic Materials</td>
			<td>400K</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Acetone</td>
			<td>Fisher Scientific</td>
			<td>A929SK-4</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Isopropyl Alcohol</td>
			<td>Fisher Scientific</td>
			<td>A459-1</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Deionized Water</td>
			<td>Fisher Scientific</td>
			<td>23-290-065</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Gold Wire</td>
			<td>DuPont</td>
			<td>5771</td>
			<td>1 mil diameter</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Chip Carrier</td>
			<td>NTK Technologies</td>
			<td>IRK28F1-5451D</td>
			<td></td>
		</tr>
	</tbody>
</table>

writing and low-temperature characterization of oxide nanostructures

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions. Oxide interfaces exhibit a wide range of properties that can be controlled include conduction, piezoelectric behavior, ferromagnetism, superconductivity and nonlinear optical properties. Recently, methods for controlling these properties at extreme nanoscale dimensions have been discovered and developed. Here are described explicit step-by-step procedures for creating LaAlO3/SrTiO3 nanostructures using a reversible conductive atomic force microscopy technique. The processing steps for creating electrical contacts to the LaAlO3/SrTiO3 interface are first described. Conductive nanostructures are created by applying voltages to a conductive atomic force microscope tip and locally switching the LaAlO3/SrTiO3 interface to a conductive state. A versatile nanolithography toolkit has been developed expressly for the purpose of controlling the atomic force microscope (AFM) tip path and voltage. Then, these nanostructures are placed in a cryostat and transport measurements are performed. The procedures described here should be useful to others wishing to conduct research in oxide nanoelectronics.

ここに示された結果は、ナノ構造のこのクラスによって示されることができ、詳細23-26の他の箇所に記載されているトランスポートの動作の代表である。この例では、ナノワイヤキャビティは、3.3単位セルLAO / STOヘテロ構造から（ 図4）を構築した。実験11」をカットする&quot;ナノワイヤーによって決定された（緑で表示）導電性パスは、幅広い一般的には10nmである。先端書き込み速度はそのまま各セグメントの先端速度と電圧は、リソグラフィのフロントパネル（ 図4B）から独立して設定可能です。 「仮想電極は、「界面接点とそのインタフェースは、ナノ構造の導電性の高い電気的な接続があることを確認してください。 ナノ構造が書き込まれた後、希釈冷凍機に転送される。 550 nmで以下光への曝露は、不要な光伝導が生成されますので、IMPですortant暗闇の中、または赤色の「暗室」は、光（ 図5A）を用いてデバイスを転送します。電気的接続はRTで行う必要があり、かつ低温での電気接続を変更するときに最も半導体ナノ構造と同様に、細心の注意を払うべきである。デバイスは静電放電に供されている場合は、最も可能性の高い絶縁性となるであろう。注目すべきことに、デバイス機能」は、サイクリング」300 Kの温度にし、再び冷却することによって回収することができる。 クールダウン中は、温度の関数として、2端子抵抗を監視するためのルーチン、さらには4端子抵抗である。交流電流は、トランスインピーダンス増幅器を使用して測定している間、これらの測定のために交流電圧（典型的には1〜7mV）は、一方の電極に低周波数（&lt;10ヘルツ）で適用される。復調にロックすると、フィルタリングは、家庭が開発し、ロックインアンプを使用して実行されます。交流のCurrent温度の関数（ 図5B）のように監視される。 装置は、希釈冷凍機（50 m·K）でのベース温度に冷却されると、四端子輸送測定（ 図5C）が行われる。デバイスの両端の電圧を同時に測定している間、これらの測定では、電流は、装置の主要なチャネルを介して供給されます。代わりに、ロックインアンプで測定する、完全な電流 - 電圧（IV）トレースを測定する。この方法は、より多くの情報が含まれており、差動伝導が数値微分を介して算出することができる。特定のデバイスについては、差動伝導はサイドゲート電圧V SGの関数として測定される。このゲートは装置の化学ポテンシャルを変化させることができる。装置を通る輸送はクーロンブロッケードが小さな値のために行われ、STROれる領域を示す、強力な非単調な依存性を示すV SGの大きな値のため、超伝導ngの。デバイスのこのクラスの物理的解釈についての詳細は他の箇所に記載する。 <img alt="図1" src="/files/ftp_upload/51886/51886fig1highres.jpg" /> 図1フォトリソグラフィ処理ステップステップ1：スピンフォトレジスト。ステップ2：マスクアライナーを用いてフォトレジストを公開します。ステップ3：フォトレジストを開発しています。ステップ4：イオンミリング。ステップ5：DCは、TiとAuを堆積させるスパッタリング。ステップ6：リフトオフ。ステップ7：第二の層を堆積させる。ステップ8：プラズマ洗浄。 <img alt="図2" src="/files/ftp_upload/51886/51886fig2highres.jpg" /> 図2。リソグラフィでパターンLAO / STOヘテロ構造のイメージ。チップキャリアに接合さ5mm x 5mmのサンプル線を示す（A）の画像。（B）<html>ボンディングパッドとキャンバスの1を示す光学像。（C）単独のキャンバスのクローズアップ。 <a href="https://www.jove.com/files/ftp_upload/51886/51886fig2highres.jpg" target="_blank">この図の拡大版を表示するには、こちらをクリックしてください。</a> <img alt="図3" src="/files/ftp_upload/51886/51886fig3highres.jpg" /> 図3。LAO / STOナノ構造の（A）非公式なデザイン。（B）は 、オープンソースのスケーラブルベクターグラフィックス（SVG）エディタを使用してナノ構造体の正確なレイアウト。 <img alt="図4" src="/files/ftp_upload/51886/51886fig4highres.jpg" /> 図4のC-AFMのパターニングのための（A）リソグラフィ、フロントパネル（B）3Dシミュレータからのスクリーンの位置とC-AFMチップの電圧を示す。w.jove.com/files/ftp_upload/52058/52058fig4large.jpg &quot;ターゲット=&quot; _blank &quot;&gt;この図の拡大版を表示するには、こちらをクリックしてください。 <img alt="図5" src="/files/ftp_upload/51886/51886fig5highres.jpg" /> の関数としてのデバイスの四端子微分コンダクタンスの図5（A）LAO / STOナノ構造は、希釈冷凍機に挿入される。試料耐性の（B）モニタリングがmKで50 300 Kから冷却される。（C）モニタリングデバイス（V4t）全体の​​サイドゲート電圧VSGと電圧。強度グラフは、ジーメンス（S）の単位で表示され、電圧はボルト（V）単位で表示されている。

Watch this Scientific Journal Video about Writing and Low-Temperature Characterization of Oxide Nanostructures at JoVE.com

Writing and Low-Temperature Characterization of Oxide Nanostructures

Oxide nanostructures provide new opportunities for science and technology. The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique. The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

書き込みおよび酸化物ナノ構造の低温特性評価

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions.  Oxide ...

writing-and-low-temperature-characterization-of-oxide-nanostructures

Research

JoVE Journal

Engineering

9.9K ビュー.  University of Pittsburgh. Oxide nanostructures provide new opportunities for science and technology. The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique. The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

ビデオ: Writing and Low-Temperature Characterization of Oxide Nanostructures

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

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen 1-7. The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion2. Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation8-12. It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition8, 10, 13, 14 ("coking") and sulfur poisoning11, 15 and the manner in which surface modifications stave off this degradation16. The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM, other properties such as local electronic states, ion diffusion coefficient and surface potential can also be investigated17-22. In this work, electrochemical measurements, Raman spectroscopy, and SPM were used in conjunction with a novel test electrode platform that consists of a Ni mesh electrode embedded in an yttria-stabilized zirconia (YSZ) electrolyte. Cell performance testing and impedance spectroscopy under fuel containing H2S was characterized, and Raman mapping was used to further elucidate the nature of sulfur poisoning. In situ Raman monitoring was used to investigate coking behavior. Finally, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) were used to further visualize carbon deposition on the nanoscale. From this research, we desire to produce a more complete picture of the SOFC anode.

We present a unique platform for characterizing electrode surfaces in solid oxide fuel cells (SOFCs) that allows simultaneous performance of multiple characterization techniques (e.g. in situ Raman spectroscopy and scanning probe microscopy alongside electrochemical measurements). Complementary information from these analyses may help to advance toward a more profound understanding of electrode reaction and degradation mechanisms, providing insights into rational design of better materials for SOFCs.

固体酸化物形燃料電池の電極表面をプロービングとマッピング

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen ...

Visible-light Induced Reduction of Graphene Oxide Using Plasmonic Nanoparticle

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using visible light irradiation with plasmonic nanoparticles. The plasmonic nanoparticle is used to improve the reduction efficiency of GO. It only takes 30 min&#160;at RT by illuminating the solutions with Xe-lamp, the r-GO solutions can be obtained by completely removing gold nanoparticles through simple centrifugation step. The spherical gold nanoparticles (AuNPs) as compared to the other nanostructures is the most suitable plasmonic nanostructure for r-GO preparation. The reduced graphene oxide prepared using visible light and AuNPs was equally qualitative as chemically reduced graphene oxide, which was supported by various analytical techniques such as UV-Vis spectroscopy, Raman spectroscopy, powder XRD and XPS. The reduced graphene oxide prepared with visible light shows excellent quenching properties over the fluorescent molecules modified on ssDNA and excellent fluorescence recovery for target DNA detection. The r-GO prepared by recycled AuNPs is found to be of same quality with that of chemically reduced r-GO. The use of visible light with plasmonic nanoparticle demonstrates the good alternative method for r-GO synthesis.

A simple protocol for the preparation of reduced graphene oxide using visible light and plasmonic nanoparticle is described.

プラズモニックナノ粒子を用いてグラフェン酸化物の可視光誘起削減

Present work demonstrates the simple, chemical free, fast, and energy efficient method to produce reduced graphene oxide (r-GO) solution at RT using ...

Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor performance, which suggest a new direction for the development of next-generation ultrathin and flexible photonic and electronic devices. Enhanced luminescence quantum efficiency has been widely observed in these atomically thin 2D crystals. However, dimension effects beyond quantum confinement thicknesses or even at the micrometer scale are not expected and have rarely been observed. In this study, molybdenum diselenide (MoSe2) layer crystals with a thickness range of 6-2,700 nm were fabricated as two- or four-terminal devices. Ohmic contact formation was successfully achieved by the focused-ion beam (FIB) deposition method using platinum (Pt) as a contact metal. Layer crystals with various thicknesses were prepared through simple mechanical exfoliation by using dicing tape. Current-voltage curve measurements were performed to determine the conductivity value of the layer nanocrystals. In addition, high-resolution transmission electron microscopy, selected-area electron diffractometry, and energy-dispersive X-ray spectroscopy were used to characterize the interface of the metal&#8211;semiconductor contact of the FIB-fabricated MoSe2 devices. After applying the approaches, the substantial thickness-dependent electrical conductivity in a wide thickness range for the MoSe2-layer semiconductor was observed. The conductivity increased by over two orders of magnitude from 4.6 to 1,500 &#937;&#8722;1 cm&#8722;1, with a decrease in the thickness from 2,700 to 6 nm. In addition, the temperature-dependent conductivity indicated that the thin MoSe2 multilayers exhibited considerably weak semiconducting behavior with activation energies of 3.5-8.5 meV, which are considerably smaller than those (36-38 meV) of the bulk. Probable surface-dominant transport properties and the presence of a high surface electron concentration in MoSe2 are proposed. Similar results can be obtained for other layer semiconductor materials such as MoS2 and WS2.

We describe the approaches for the device fabrication and electrical characterization of molybdenum diselenide (MoSe2) layer semiconductor nanostructures with different thicknesses. In addition, the fabrication of ohmic contacts for MoSe2-layer nanocrystals by the focused-ion beam deposition method using platinum (Pt) as a contact metal is described.

レイヤ半導体ナノ構造のための集束イオンビーム技術と電気的評価を使用したオーミックコンタクト製作

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor ...

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

半導体技術との互換性低温カーボンナノチューブ垂直相互接続の作製

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

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 ...

Writing Bragg Gratings in Multicore Fibers

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

We describe a technique for inscribing identical fiber Bragg gratings into each core of a multicore fiber. This is achieved by introducing an additional surface into the optical path to mitigate lensing by the curved surface of the fiber cladding.

マルチコアファイバーブラッググレーティングを書きます

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong ...

Iridium Oxide-reduced Graphene Oxide Nanohybrid Thin Film Modified Screen-printed Electrodes as Disposable Electrochemical Paper Microfluidic pH Sensors

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use integrated paper microfluidic electrochemical pH sensor for resource-limited settings. Taking advantages from both pH meters and strips, the pH sensing platform is composed of hydrophobic barrier-patterned paper micropad (&#181;PAD) using polydimethylsiloxane (PDMS), screen-printed electrode (SPE) modified with IrO2-graphene films and molded acrylonitrile butadiene styrene (ABS) plastic holder. Repetitive cathodic potential cycling was employed for graphene oxide (GO) reduction which can completely remove electrochemically unstable oxygenated groups and generate a 2D defect-free homogeneous graphene thin film with excellent stability and electronic properties. A uniform and smooth IrO2 film in nanoscale grain size is anodically electrodeposited onto the graphene film, without any observable cracks. The resulting IrO2-RGO electrode showed slightly super-Nernstian responses from pH 2-12 in Britton-Robinson (B-R) buffers with good linearity, small hysteresis, low response time and reproducibility in different buffers, as well as low sensitivities to different interfering ionic species and dissolved oxygen. A simple portable digital pH meter is fabricated, whose signal is measured with a multimeter, using high input-impedance operational amplifier and consumer batteries. The pH values measured with the portable electrochemical paper-microfluidic pH sensors were consistent with those measured using a commercial laboratory pH meter with a glass electrode.

The study demonstrates the growth of iridium oxide-reduced graphene oxide (IrO2-RGO) nanohybrid thin films on irregular and rough screen-printed carbon substrate through a green electrochemical synthesis, and their implementation as a pH sensor with a patterned paper-fluidic platform.

使い捨て電気化学紙のマイクロ流体のpHセンサーとしてイリジウム酸化還元グラフェン酸化物ナノハイブリッド薄膜変更されたスクリーン印刷電極

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

新規材料の低温磁気伝導測定のための高度な実験方法

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Method Development for Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper

The current analytical techniques for characterizing printing and graphic arts substrates are largely ex situ and destructive. This limits the amount of data that can be obtained from an individual sample and renders it difficult to produce statistically relevant data for unique and rare materials. Resonant cavity dielectric spectroscopy is a non-destructive, contactless technique which can simultaneously interrogate both sides of a sheeted material and provide measurements which are suitable for statistical interpretations. This offers analysts the ability to quickly discriminate between sheeted materials based on composition and storage history. In this methodology article, we demonstrate how contactless resonant cavity dielectric spectroscopy may be used to differentiate between paper analytes of varying fiber species compositions, to determine the relative age of the paper, and to detect and quantify the amount of post-consumer waste (PCW) recycled fiber content in manufactured office paper.

A protocol for the non-destructive analysis of the fiber content and relative age of paper.

セルロース系紙の非接触共振キャビティ誘電分光研究の方法開発

The current analytical techniques for characterizing printing and graphic arts substrates are largely ex situ and destructive. This limits the amount of ...