私たちは、有益な議論のためのKYタン、P.参照およびGC Tettamanziに感謝します。我々は、オーストラリアの研究評議会（認可番号DP120104710）、フィンランドアカデミー（認可番号251748、135794、272806）およびデバイス製造のためのオーストラリア国立加工施設からのサポートからの財政支援を認めます。 ARは、ニューサウスウェールズ大学の初期のキャリア研究の助成スキームからの財政支援を認めるものです。 MicroNova社ナノファブリケーションセンターのアールト大学の設備と技術サポートの提供も認められています。

注：このプロトコルは、製造、パッケージとシリコンMOS QD技術に基づいた単一電子ポンプをテストするために使用する手順について説明します。項3のものはISO6研究所で行われている間、サブセクション1及び2で説明したステップは、ISO5クリーンルームで行われます。周囲条件を連続的に制御されます。温度と湿度の公称値は、それぞれ、20±1℃、55％±5％に設定されています。 1.微細加工<ol><li>フィールド酸化物<ol><li>以下に浸漬することによって、ウエハを清掃してください：ピラニアエッチング（10分）、脱イオン（DI）水（10分）、RCA-2溶液（DI水175ミリリットル、塩酸30ミリリットル、H 2 O 2 30ミリリットル、100℃で10分間）を水に10希釈し、脱イオン水（5分）、フッ化水素（HF）酸：1（10秒）、DI水（10分）。 HF（ すなわち 、ゴーグル、PVCエプロン、とPVC手袋）を取り扱う際は防護服を使用してください。順に進みます。 </li><li>ウエハを配置900℃での酸化炉で、次のように段階的に酸化する：ドライO 2（10分）、湿潤O 2（40分）、ドライO 2（10分）、N 2（15分）。 </li></ol></li><li>オーミックコンタクト<ol><li>フォトリソグラフィとエッチングの酸化を行います。 <ol><li>次のようにウエハ表面上に接着促進ヘキサメチルジシラザン（HMDS）の数nmの厚さの層を堆積させる：プリベークをホットプレート上で110℃で1分間、ガラスビーカーにHMDSの約50ミリリットル注ぎ、ビーカーを置きます真空チャンバ内のウエハは、避難、2分間待ちます。 </li><li>バックとウェハ（3,000〜5,000 rpmで、所望の厚さに応じて25〜40秒）の前面両側のフォトレジストの2-4μmの厚さの層をスピン。 </li><li>マスクアライナーで紫外光に露出させ（4-10秒を10mW / cm 2の厚さに抵抗するようによります）。 1分間110℃のホットプレート上でポストベーク。 </li><li>次いで脱イオン水ですすぎ、1〜2分間の開発。 </LI&gt; <li> 20分間O 2プラズマエッチングを行う（;入射パワー= 50 W;圧力= 340ミリトール反射電力を&lt;1 W）。 </li><li>緩衝HF酸エッチング溶液中で酸化物（15：1、4-5分、30℃で≈速度は20nm /分のエッチング）。脱イオン水（5分）ですすいでください。 N 2でブロー乾燥。 </li></ol></li><li>アセトンに浸漬することにより、フォトレジストを除去します。イソプロパノール（IPA）で、その後、N 2でブロー乾燥すすいでください。 </li><li> （所望のドーピング濃度に応じて30〜45分間、N 2流量）リン源と1000℃の炉内でウェハを配置します。 </li><li>脱イオン水（10分）ですすぎ、水で希釈したHF酸（1、3-4分間、30℃でのエッチング速度≈は40nm / minで10）で汚染された酸化物層を除去します。 </li><li> 1.1.2のように酸化します。 </li></ol></li><li>ゲート酸化物<ol><li>繰り返しは1.2.1と1.2.2を繰り返します。 </li><li> 800℃で、専用の炉内でウェハを置き、次のように段階的に酸化する：ドライO 2（10分）、Dichloroethylene + O 2（20分）、ドライO 2（所望の酸化物の厚さに応じて10〜30分）、N 2（15分）。 </li></ol></li><li>オーミックコンタクトのメタライゼーション<ol><li>手順を繰り返し1.2.1。 </li><li>電子ビーム蒸発器内のウエハを配置します。 0.2〜0.5ナノメートル/秒、5×10 -6トルで100nmのアルミニウムを蒸発させます。 </li><li>金属をリフトオフするために1時間80℃でホットプレート上でNメチル-2-ピロリドン（NMP）中にウェハを浸します。必要に応じて超音波攪拌を使用してください。 2分間IPAですすいでください。 N 2でブロー乾燥。 </li><li>少なくとも15分間、400℃で形成ガスでアニール。 </li></ol></li></ol> 2.ナノ加工<ol><li>ウェーハダイシング<ol><li>いずれかが（ポリマーおよび紡糸パラメータの種類は、この段階では無関係である）保護コーティングとして機能するように、ウェハ上にレジストをスピン。 </li><li> 〜10×2 mm 2での個々のチップにウェハを切断するためにダイヤモンドチップダイサーを使用してください。 </li></ol></li><li>クリーニング<ol><li>その後2分間IPAですすぎ、80℃のホットプレート上で1時間、NMP中に浸します。 N 2でブロー乾燥。 </li><li> 5分間O 2プラズマエッチングを行う（= 50 W入射電力、反射電力を&lt;1 W）。 </li><li>アセトン、IPAでクリーンスピン（7,500 rpmで、30秒） </li></ol></li><li>アライメントマーカパターニング<ol><li>スピンポリメチルメタクリレート（PMMA 950k）はA4は（30秒が所望の厚さに応じて、5,000-7,500 rpm）をレジスト。典型的な加工厚≈150〜200ナノメートル。 90秒間180℃のホットプレート上にレジストを焼きます。 </li><li>電子ビームリソグラフィを実施しています。次の書き込み条件を使用し= 30keVのビームエネルギー、ビーム電流≈30 PA、面積線量500〜650μC/ cm 2でのマーカーの大きさに応じて≈およびレジスト厚。 </li><li> （1：3）40〜60秒間、その後20秒間IPAですすぎ、メチルイソブチルケトン、IPA溶液のレジストの開発。 N 2銃でブロー乾燥。 </li><li>場所電子ビーム蒸発器内のチップ。 0.2〜0.4ナノメートル/秒、5×10 -6トルでのTiの15 nmおよびPtを65ナノメートルを蒸発させます。 </li><li>ステップ1.4.3のように金属を持ち上げ。 </li><li>ステップのようにきれいなチップ2.2.2-2.2.3。 </li></ol></li><li>ゲートパターニング<ol><li>スピンは、2.3.1のように抵抗します。 </li><li>電子ビームリソグラフィを実施しています。 = 30 keVのビームエネルギー、ビーム電流≈30 PA、面積線量≈は500〜700μC/ cm 2の高解像度の特徴については、以下の書き込み条件を使用してください。低解像度の機能のための条件を書く：= 15 keVのビームエネルギー、ビーム電流≈10 nAの、面積線量400〜600μC/ cm 2の ≈。 </li><li> 2.3.3のようにレジストを開発します。 </li><li>熱蒸発器内のチップを配置します。 0.1〜0.4ナノメートル/秒、1-9×10 -6ミリバールでのAlを蒸発させます。目標厚さは、レイヤ1のためのレイヤ数に応じて、 図2（b）に示すように（25〜35ナノメートル、レイヤ2、75〜90 45〜65 nmのために変化するn個レイヤ3のためのM）。 </li><li>ステップ1.4.3のように金属を持ち上げ。 </li><li> 5〜10分間、150℃のホットプレート上でのAlの酸化を行います。 </li><li>ステップ2.2.3のようにきれいなチップ。 </li><li>手順を繰り返し二回3層ゲートスタックを実現する2.4.1-2.4.7。 </li></ol></li></ol> 3.デバイスのパッケージング<ol><li>ステップ2.1のようにサイコロチップ</li><li> 2分間アセトン及びIPAの結果小さなチップをすすぎます。 </li><li> PMMA A5を有するプリント回路基板（PCB）の個片を接着。それが乾燥するために2分を待ちます。あるいは、熱化を強化するために、銀エポキシ樹脂を使用しています。 </li><li>ウェッジボンダにPCBをロードして、配線を進めます。 </li></ol> 4.デバイスの完全性テスト<ol><li>ディッププローブに有線デバイスを含むPCBをマウントします。 </li><li>ディッププローブのものにPCBの電線を配線します。 </li><li>液体ヘリウムを含む容器内にプローブを挿入します。過剰なヘリウムbを避けるために、ゆっくりと進みオイルオフ。 </li><li>接地他のゲートを維持しながら、各デバイスのゲートについては、ソースメジャーユニットへのプローブの対応する室温の電極を接続してください。数NAにコンプライアンス電流を設定します。 、0.1 Vのステップで1.5Vにゼロからの電圧を掃引測定し、電流を記録します。 </li><li>バッテリ駆動の可変DC電圧源に各ゲート線を接続し、内蔵のロックインアンプの交流電圧源、及びロックイン増幅器の入力ポートにドレイン線にソース線。 </li><li> （ 図4参照）は、異なるゲート電圧の設定のためのコンダクタンスを排出するソースを測定します。 <ol><li>グローバル接地C1とC2ゲートを維持することによりゲートBL、BR、PL、SLおよびDLに印加される電圧をランプアップ。 「ターン·オン」デバイス特性を記録します。 </li><li>個別に各ゲート電圧を下降し、ゲート「ピンチオフ」の特性を記録します。 </li><li>静電クを定義するためにゲート電圧を調整しますターンオン電圧より（大きい）、BLとBR（PL、SLおよびDL）の電圧を設定することによりアントゥムドット小さいです。クーロンブロッケード特性を記録します。 </li></ol></li></ol>

<ol>
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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=Stabilization+of+single-electron+pumps+by+high+magnetic+fields.">Stabilization of single-electron pumps by high magnetic fields.</a> Phys. Rev. B. 86 (15), 155311-1-155311-6 (2012).</li><li>Kataoka, M., 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=Tunable+Nonadiabatic+Excitation+in+a+Single-Electron+Quantum+Dot.">Tunable Nonadiabatic Excitation in a Single-Electron Quantum Dot.</a> Phys. Rev. Lett. 106 (12), 126801-1-126801-4 (2011).</li></ol>

著者らは、開示することは何もありません。

本論文で報告されたプロトコルは、その機能の完全性をテストし、単電子ポンプとして、それらを動作させるために、シリコンMOSのQD、ならびに実験手順を製造するための技術について説明します。注目すべきことに、ゲート設計を調整することによって、同一の製造工程では、量子ビットの読み出しおよび制御17に適し、ならびに12,13チャージポンプデバイスを製造するために使用することができます。我々は、この記事で引用されたプロセスの多くのパラメータは（キャリブレーション、作るか、またはモデル）を使用し、製造ツールのと同様に、シリコン基板（厚さとバックグラウンドドーピング密度）の種類に応じて変えることができることに注意してください。そのようなリソグラフィ露光量または現像時間、エッチングや酸化時間等の数量は、慎重に較正されかつ信頼性の高い歩留まりを確保するためにテストされなければなりません。さらに、異なるプロセスのために同じ製造ツールの使用に起因するクロスコンタミネーションを避けるために重要です。この目的のために、数のCriticalステップはもっぱら、金属蒸発、酸素炉とHF浴などのシリコン処理専用の機器を用いて実施されます。 より一般的には、シリコンは、チャージポンプ18〜20を実現するための最適な材料として関心の高まりを描いています。これは、一部の業界互換のシリコンプロセスを使用して、新しい量子ベース電流の標準を実装する魅力的観点によるものです。これは、スケーラビリティ、並列駆動のオーバーヘッドのためのよく確立され、信頼性の高い統合技術の恩恵を受けるだろう。重要なことには、ゲート材料のような伝統的な金属を含まない完全な相補型MOS（CMOS）技術は、単一の電子デバイス21に大幅に減少した背景の電荷の変動を示しています。このような変動は計量精度を達成するために有害であることができます。 ここで説明するプロトコルは、金属ゲートを有するMOSナノデバイスの実現に制限されています。したがって、achieへ完全な産業適合性をまして電荷変動を低減するには、ゲート堆積技術を変更し、ゲート材料として高濃度にドープされた多結晶シリコンを使用するために必要とされるであろう。 結論として、ここで説明したMOS QDポンプは最近、正確な電流発生13の面で非常に優れた性能を有するシリコンの技術的利点を組み合わせています。これは、1つは、コンパクトで汎用性の高いシステムにつながる複数のゲート層を積層することを可能にする設計及び製造プロセスの高い柔軟性に由来します。一緒に背景の電荷の変動を減少させる可能性のあるドットの静電閉じ込めの結果として生じる微調整可能性は、他の半導体のポンプ22,23で観察された主な課題を克服するための段階を設定します。

Silicon is the material of choice for most of the modern microelectronics. Its properties, combined with advanced lithographic techniques, have allowed the semiconductor industry to achieve very large-scale integration and deliver billions of transistors per chip. The metal-oxide-semiconductor (MOS) technology1 has been the key of this relentless technological progress2. In brief, it is based on a selectively doped Si substrate which is thermally oxidized to grow a high quality SiO2 gate oxide on which a metal gate electrode is deposited. Recently, it has been shown that the use of a stack of gate oxides could be beneficial3 . While present industry standards have reached minimum feature sizes for gate lengths below 20 nm, it is becoming increasingly evident that, at this level of miniaturization, detrimental quantum mechanical phenomena come into play that may complicate further downscaling4.
Remarkably, silicon is also an excellent host material to exploit the quantum properties of the electron charge and spin5. This has broadened its range of applicability to entirely new fields such as quantum computing6 and quantum electrical metrology7. Among other approaches5, the use of a multi-gate MOS technology8,9 has led to electrostatically-defined quantum dots (QD) whose occupancy can be controlled down to single-electron level10. Unlike the conventional MOS process where just one gate per transistor is needed1, these QDs are defined via a three-layer stack of Al/AlyOx gates which are used to selectively accumulate electrons at the Si/SiO2 interface, as well as provide lateral and vertical confinement11.
Although these devices had been originally developed for quantum computing applications, they have also recently shown promising performances as metrological tools12,13. In the field of quantum electrical metrology, a long-standing goal is the redefinition of the unit ampere in terms of the elementary charge (e) 14. In particular, the emphasis is on the realization of nano-scale charge pumps to clock the transfer of individual electrons timely and accurately. These devices generate macroscopic quantized electric currents, I=nef, where f is the frequency of an external driving oscillator and n is an integer. To date, the best performance has been achieved with a GaAs-based pump by yielding a current in excess of 150 pA with a relative uncertainty of 1.2 parts per million15. Recently, silicon MOS QDs have also stood out for the implementation of highly accurate single-electron pumps thanks to the capability of finely tuning the charge confinement13.
Here, we discuss the protocol used for the fabrication of silicon MOS QDs. Furthermore, the cryogenic set-up used to test the integrity of the devices after fabrication and the one to perform charge pumping experiments are described. Finally, representative measurements of quantized electric current are reported.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Silicon wafers</td>
			<td>TOPSIL</td>
			<td></td>
			<td>4 inch</td>
		</tr>
		<tr>
			<td>Electron-beam lithography machine</td>
			<td>Raith gmbh</td>
			<td></td>
			<td>Raith 150two</td>
		</tr>
		<tr>
			<td>E-beam resist&#160;</td>
			<td>MicroChem gmbh</td>
			<td></td>
			<td>PMMA</td>
		</tr>
		<tr>
			<td>Photoresist</td>
			<td>MicroChem gmbh</td>
			<td></td>
			<td>nLOF2020</td>
		</tr>
		<tr>
			<td>Mask aligner</td>
			<td>Quintel</td>
			<td></td>
			<td>Q6000</td>
		</tr>
		<tr>
			<td>Photoresist developer</td>
			<td>MicroChem gmbh</td>
			<td></td>
			<td>AZ826MIF</td>
		</tr>
	</tbody>
</table>

silicon metal-oxide-semiconductor quantum dots for single-electron pumping

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization.

Watch this Scientific Journal Video about Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping at JoVE.com

Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping

The fabrication process and experimental characterization techniques relevant to single-electron pumps based on silicon metal-oxide-semiconductor quantum dots are discussed.

単電子揚水用のシリコン金属酸化膜半導体量子ドット

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by ...

silicon-metal-oxide-semiconductor-quantum-dots-for-single-electron

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Unit 1

Basics of Semiconductors

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14.2K ビュー.  University of New South Wales. The fabrication process and experimental characterization techniques relevant to single-electron pumps based on silicon metal-oxide-semiconductor quantum dots are discussed.

ビデオ: Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping

Compact Quantum Dots for Single-molecule Imaging

Single-molecule imaging is an important tool for understanding the mechanisms of biomolecular function and for visualizing the spatial and temporal heterogeneity of molecular behaviors that underlie cellular biology 1-4. To image an individual molecule of interest, it is typically conjugated to a fluorescent tag (dye, protein, bead, or quantum dot) and observed with epifluorescence or total internal reflection fluorescence (TIRF) microscopy. While dyes and fluorescent proteins have been the mainstay of fluorescence imaging for decades, their fluorescence is unstable under high photon fluxes necessary to observe individual molecules, yielding only a few seconds of observation before complete loss of signal. Latex beads and dye-labeled beads provide improved signal stability but at the expense of drastically larger hydrodynamic size, which can deleteriously alter the diffusion and behavior of the molecule under study.
Quantum dots (QDs) offer a balance between these two problematic regimes. These nanoparticles are composed of semiconductor materials and can be engineered with a hydrodynamically compact size with exceptional resistance to photodegradation 5. Thus in recent years QDs have been instrumental in enabling long-term observation of complex macromolecular behavior on the single molecule level. However these particles have still been found to exhibit impaired diffusion in crowded molecular environments such as the cellular cytoplasm and the neuronal synaptic cleft, where their sizes are still too large 4,6,7.
Recently we have engineered the cores and surface coatings of QDs for minimized hydrodynamic size, while balancing offsets to colloidal stability, photostability, brightness, and nonspecific binding that have hindered the utility of compact QDs in the past 8,9. The goal of this article is to demonstrate the synthesis, modification, and characterization of these optimized nanocrystals, composed of an alloyed HgxCd1-xSe core coated with an insulating CdyZn1-yS shell, further coated with a multidentate polymer ligand modified with short polyethylene glycol (PEG) chains (Figure 1). Compared with conventional CdSe nanocrystals, HgxCd1-xSe alloys offer greater quantum yields of fluorescence, fluorescence at red and near-infrared wavelengths for enhanced signal-to-noise in cells, and excitation at non-cytotoxic visible wavelengths. Multidentate polymer coatings bind to the nanocrystal surface in a closed and flat conformation to minimize hydrodynamic size, and PEG neutralizes the surface charge to minimize nonspecific binding to cells and biomolecules. The end result is a brightly fluorescent nanocrystal with emission between 550-800 nm and a total hydrodynamic size near 12 nm. This is in the same size range as many soluble globular proteins in cells, and substantially smaller than conventional PEGylated QDs (25-35 nm).

We describe the preparation of colloidal quantum dots with minimized hydrodynamic size for single-molecule fluorescence imaging. Compared to conventional quantum dots, these nanoparticles are similar in size to globular proteins and are optimized for single-molecule brightness, stability against photodegradation, and resistance to nonspecific binding to proteins and cells.

1分子蛍光イメージングのためのコンパクトな量子ドット

Single-molecule imaging is an important tool for  understanding the mechanisms of biomolecular function and for visualizing the  spatial and temporal ...

工学

Gradient Echo Quantum Memory in Warm Atomic Vapor

Gradient echo memory (GEM) is a protocol for storing optical quantum states of light in atomic ensembles. The primary motivation for such a technology is that quantum key distribution (QKD), which uses Heisenberg uncertainty to guarantee security of cryptographic keys, is limited in transmission distance. The development of a quantum repeater is a possible path to extend QKD range, but a repeater will need a quantum memory. In our experiments we use a gas of rubidium 87 vapor that is contained in a warm gas cell. This makes the scheme particularly simple. It is also a highly versatile scheme that enables in-memory refinement of the stored state, such as frequency shifting and bandwidth manipulation. The basis of the GEM protocol is to absorb the light into an ensemble of atoms that has been prepared in a magnetic field gradient. The reversal of this gradient leads to rephasing of the atomic polarization and thus recall of the stored optical state. We will outline how we prepare the atoms and this gradient and also describe some of the pitfalls that need to be avoided, in particular four-wave mixing, which can give rise to optical gain.

The gradient echo memory is a protocol for storing optical quantum states of light in atomic ensembles. Quantum memory is a key element of a quantum repeater, which can extend the range of quantum key distribution. We outline the operation of the scheme when implemented in a 3-level atomic ensemble.

暖かい原子蒸気に勾配エコー量子メモリ

Gradient  echo memory (GEM) is a protocol for storing optical quantum states of light in  atomic ensembles. The primary motivation for such a technology ...

Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and entanglement, to solve certain problems exponentially faster than with the best known algorithms on a classical computer. Gate-defined lateral quantum dots on GaAs/AlGaAs are one of many avenues explored for the implementation of a qubit. When properly fabricated, such a device is able to trap a small number of electrons in a certain region of space. The spin states of these electrons can then be used to implement the logical 0 and 1 of the quantum bit. Given the nanometer scale of these quantum dots, cleanroom facilities offering specialized equipment- such as scanning electron microscopes and e-beam evaporators- are required for their fabrication. Great care must be taken throughout the fabrication process to maintain cleanliness of the sample surface and to avoid damaging the fragile gates of the structure. This paper presents the detailed fabrication protocol of gate-defined lateral quantum dots from the wafer to a working device. Characterization methods and representative results are also briefly discussed. Although this paper concentrates on double quantum dots, the fabrication process remains the same for single or triple dots or even arrays of quantum dots. Moreover, the protocol can be adapted to fabricate lateral quantum dots on other substrates, such as Si/SiGe.

This paper presents a detailed fabrication protocol for gate-defined semiconductor lateral quantum dots on gallium arsenide heterostructures. These nanoscale devices are used to trap few electrons for use as quantum bits in quantum information processing or for other mesoscopic experiments such as coherent conductance measurements.

ゲート定義のGaAs / AlGaAs系横量子ドットのナノファブリケーション

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and ...

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.
As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz&frac12; at 0.3 K 5.

Scanning-probe single-electron capacitance spectroscopy facilitates the study of single-electron motion in localized subsurface regions. A sensitive charge-detection circuit is incorporated into a cryogenic scanning probe microscope to investigate small systems of dopant atoms beneath the surface of semiconductor samples.

走査プローブ単電子容量分光

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

Analysis of Contact Interfaces for Single GaN Nanowire Devices

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit a strong degradation after annealing due to the occurrence of void formation at the contact/SiO2 interface. This void formation can cause cracking and delamination of the metal film, which can increase the resistance or lead to a complete failure of the NW device. In order to address issues associated with void formation, a technique was developed that removes Ni/Au contact metal films from the substrates to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN NW devices. This procedure determines the degree of adhesion of the contact films to the substrate and NWs and allows for the characterization of the morphology and composition of the contact interface with the substrate and nanowires. This technique is also useful for assessing the amount of residual contamination that remains from the NW suspension and from photolithographic processes on the NW-SiO2 surface prior to metal deposition. The detailed steps of this procedure are presented for the removal of annealed Ni/Au contacts to Mg-doped GaN NWs on a SiO2 substrate.

A technique was developed that removes Ni/Au contact metal films from their substrate to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN nanowire devices.

シングルGaNナノ細線デバイスのための接触界面の解析

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit  a strong degradation after annealing due to the  occurrence of void formation at the ...

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms.
In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station.

A detailed procedure for surface doping of Silicon interfaces is provided. The ultra-shallow surface doping is demonstrated by using phosphorus containing monolayers and rapid annealing process. The method can be used for doping of macroscopic area surfaces as well as nanostructures.

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra ...

Fabrication of Uniform Nanoscale Cavities via Silicon Direct Wafer Bonding

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned and bonded silicon wafers. Unlike confinements in porous materials often used for these types of experiments3, bonded wafers provide predesigned uniform spaces for confinement. The geometry of each cell is well known, which removes a large source of ambiguity in the interpretation of data.
Exceptionally flat, 5 cm diameter, 375 &#181;m thick Si wafers with about 1 &#181;m variation over the entire wafer can be obtained commercially (from Semiconductor Processing Company, for example). Thermal oxide is grown on the wafers to define the confinement dimension in the z-direction. A pattern is then etched in the oxide using lithographic techniques so as to create a desired enclosure upon bonding. A hole is drilled in one of the wafers (the top) to allow for the introduction of the liquid to be measured. The wafers are cleaned2 in RCA solutions and then put in a microclean chamber where they are rinsed with deionized water4. The wafers are bonded at RT and then annealed at ~1,100 &#176;C. This forms a strong and permanent bond. This process can be used to make uniform enclosures for measuring thermal and hydrodynamic properties of confined liquids from the nanometer to the micrometer scale.

A method for permanently bonding two silicon wafers so as to realize a uniform enclosure is described. This includes wafer preparation, cleaning, RT bonding, and annealing processes. The resulting bonded wafers (cells) have uniformity of enclosure ~1%1,2. The resulting geometry allows for measurements of confined liquids and gasses.

シリコン直接ウェハー接合による均一ナノスケールキャビティの作製

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned ...

Construction and Characterization of External Cavity Diode Lasers for Atomic Physics

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs1,2. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling1,2 makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman3, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included.

This is an instructional paper to guide the construction and diagnostics of external cavity diode lasers (ECDLs), including component selection and optical alignment, as well as the basics of frequency reference spectroscopy and laser linewidth measurements for applications in the field of atomic physics.

原子物理学外部共振器半導体レーザーの構築とキャラクタリゼーション

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

液体環境におけるパルスUVレーザー照射によるシリコン表面の濡れ性の選択エリア変更

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

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 ...