This work was supported by the Natural Science and Engineering Research Council of Canada (Discovery Grant No. 122795-2010) and the program of the Canada Research Chair in Quantum Semiconductors (JJD). The help provided by Xiaohuan Xuang, Mohamed Walid Hassen and technical assistance of Sonia Blais of the Universit&#233; de Sherbrooke Centre de caract&#233;risation de mat&#233;riaux (CCM) in collecting XPS data are greatly appreciated. NL acknowledges the Merit Scholarship Program for Foreign Student, Fonds de recherche du Qu&#233;bec - Nature et technologies, for providing a graduate student scholarship.

1. Probenvorbereitung <ol><li> Verwenden eine diamode Schreiber, eine n-Typ zu spalten (P-dotiert) einseitig polierten Si-Wafer (spezifischer Widerstand 3,1 ~ 4,8 Ω.m), die 3 Zoll im Durchmesser, 380 um dick, in Proben von 12 mm x 6 mm; Reinigen der Proben in Opticlear, Aceton und Isopropylalkohol (5 min für jeden Schritt). </li><li> Etch Proben in einem ~ 0,9% HF-Lösung für 1 min wegzuätzen anfänglichen Oxid; Spülen in DI-Wasser und trocken in hoher Reinheit (99,999%), Stickstoff (N 2). </li><li> Shop hergestellten Proben in N 2 Tasche, um ihre Oxidation an Luft zu bändigen. </li></ol> 2. Bestrahlen Proben von ArF (λ = 193 nm) und KrF (λ = 248 nm) Laser. <ol><li> Prüfmuster in einer 0,74 mm hoch Kammer und versiegeln die Kammer mit einem Quarzglasfenster, das eine hohe Transmission im UV (≥90%) hat. Füllen Sie die Kammer mit H 2 O 2 / H 2 O-Lösung im Bereich von 0,01 bis 0,2% oder mit entgastem methanol mit einem mikrofluidischen Kanal. </li><li> Bestrahlen Proben homogenisiert ArF- oder KrF-Laser bei Verkleinerung von 2,6 bzw. 1,8. Bestrahlen nur 2 Seiten auf jeder Probe durch Erhöhen Laserpulse von 100 bis 600 in Schritten von 100 Impulsen durch eine kreisförmige Maske (4 mm im Durchmesser). Bestrahlen der Proben in der gleichen Weise mit einem &quot;Ahornblatt&quot; (9 mm x 7,2 mm) Maske. </li><li> Rinse Proben in DI-Wasser, trocken mit N 2 bündig; legen Sie die Proben in einem verschlossenen Behälter, dann schnell diese Behälter zu füllen mit N 2, um die Exposition gegenüber Luft vor weiteren Versuchen zu vermeiden. </li></ol> 3. Immobilisierung von Bio-konjugierten Nanokugeln <ol><li> Verdünnte Biotin-konjugiertem Fluorescein gefärbt und 40 nm Durchmesser in Nanosphären pH 7,4 Phosphat-gepufferter Saline (PBS, 1x) Lösung bis 10 12 Partikel / ml bei Raumtemperatur (~ 25 ° C). Tauchen ArF oder KrF-Laser bestrahlten Proben für 2 &amp;# 160; hr in diese Lösung bei RT. </li><li> Waschproben mit PBS auf physikalisch gebundenem Fluorescein gefärbten Nanokügelchen an der Oberfläche zu beseitigen. </li></ol> 4. Oberflächencharakterisierung <ol><li> Kontaktwinkel (CA) Mess <ol><li> Führen Sie statische CA Messungen mit einem Winkelmesser in einem Umfeld von RT und Umgebungsfeuchte. </li><li> Beschäftigen hochreinem entionisiertem Wasser (spezifischer Widerstand 17,95 M &amp; Omega; · cm) in einer Mikrospritze; erzeugen ähnliches Volumen (~ 5 &amp; mgr; l) Tropfen auf die Probenoberfläche durch Absenken des Mikrospritze auf eine ähnliche Höhe für jede Messung. </li><li> Erfassen und speichern die Wassertropfen Profilbilder von CCD-Kamera mit Software. Messung unabhängig 4 verschiedene Standorte mit gleichen Bestrahlungsbedingungen. </li><li> Schätzung und der Mittelwert der CA-Werte in Drop-Analysemodul von ImageJ-Software; laden Sie das Bild und ändern Sie es in Graustufen; starten Sie das Plugin Dropsnake; setzen etwa ein paar Knoten an der Tropfenkontur (~ 10 Knoten) von links nachRecht, Schlange zu initialisieren; nehmen die Kurve Verbinden dieser Knoten und entwickeln sich die Kurve durch Drücken Schlange Taste. Hinweis: Kontaktwinkel sind in dem Bild und der Tabelle angezeigt. </li></ol></li><li> XPS-Messung <ol><li> Untersuchen Oberfläche chemische Modifikation mit einem XPS-Spektrometer (1x10 -9 Torr Basisdruck) mit einem Al-Ka Quelle arbeitet bei 150 W ausgestattet: <ol><li> Laden Sie die Proben in die Vakuumkammer. </li><li> Erwerben Sie die Oberfläche Umfragedaten in konstanten Energiearten 50 eV Pass Energie von einer Fläche von 220 um x 220 um. </li><li> Erwerben Sie hochauflösende Scans von Daten aus dem gleichen Untersuchungsgebiet bei 20 eV übergeben Energie. </li></ol></li><li> Prozess XPS-Spektren Daten mit XPS-Spektren Quantifizierungssoftware, wie verwiesen 25,26. </li></ol></li><li> Fluoreszenzmikroskop Bildgebung <ol><li> Excite Proben, die durch Maske &quot;Ahornblatt&quot; bestrahlt und Buntnanokugeln Fluorescein ausgesetzt waren, unter Verwendung voneine blaue Lichtquelle (λ = 450 ~ 490 nm). </li><li> Beobachten fluoreszierenden Bildern, Emission bei 515 nm mit einem Fluoreszenz-Umkehrmikroskops in Vergrößerung 4X. </li><li> Prägen die Oberflächenmorphologie dieser Proben mit AFM, wie verwiesen. 27 </li></ol></li></ol>

The authors have nothing to disclose.

Wir haben ein Protokoll des UV-Laser-Bestrahlung des Si-Wafer in einem mikrofluidischen Kammer mit niedriger Konzentration von H 2 O 2 Lösung gefüllt, um eine superhydro Si-Oberfläche, die im Wesentlichen zu induzieren aufgrund der Erzeugung von Si-OH vorgeschlagen. UV Laserphotolyse H 2 O 2 sollte negativ geladenen OH bilden - Radikalen. Außerdem führt UV-Laserphotoeffekt zur Ausbildung eines positiv geladenen Oberfläche 37. Daher ist die Wechselwirkung dieser negativen...

Die bemerkenswerten elektronischen und chemischen Eigenschaften sowie die hohe mechanische Festigkeit haben, Silizium (Si) eine ideale Wahl für mikroelektronische Bauelemente und biomedizinische Chips 1 gemacht. Selektives Steuerung der Si-Oberfläche hat erhebliche Aufmerksamkeit für Anwendungen, die mikrofluidische und Lab-on-Chip-Bausteine ​​2,3 .Diese wird häufig entweder durch nanoskalige Modifikation der Oberflächenrauhigkeit oder durch chemische Behandlung der Oberfläche 4 erhalten. Die Oberfläche Aufrauen oder Mustern zu ungeordneten oder geordneten Oberflächenstrukturen auf der Si-Oberfläche zu erzeugen sind Photolithographie 5, Ionenstrahl-Lithographie 6 und Lasertechniken 7. Im Vergleich zu diesen Verfahren wird Laseroberflächenstrukturierung Prozess gemeldet weniger kompliziert mit dem Potenzial, Mikrostrukturen mit hoher räumlicher Auflösung 8 herzustellen sein. Da Si eine erhöhte Texturierung Schwellenwert erfordern Bestrahlung mit Pulsfluenz uminduzieren Oberflächentexturierung über seine Abtrageschwelle (~ 500 mJ / cm 2) 9 hat Texturierung der Si-Oberfläche häufig durch Verwendung reaktiver Gasatmosphäre, wie die von einem Hochdruck-SF6 Umgebung 4,7,8 unterstützt worden. Folglich, um die Benetzbarkeit der Si-Oberfläche zu modifizieren, wurden zahlreiche Arbeiten über chemische Behandlung durch Abscheiden von organischen und anorganischen Schichten 10 2, oder unter Verwendung von Plasma oder Elektronenstrahl-Oberflächenbehandlung 11,12 konzentriert. Es ist, dass die Hydrophilie von Si aus der Existenz von singulären und zugehörige OH-Gruppen auf seiner Oberfläche Ursprung könnte durch Kochen in einer H 2 O 2 -Lösung bei 100 ° C für mehrere Minuten 13 erreicht werden erfasst. Jedoch die hydrophoben Si Oberflächenzustände, von denen die meisten aufgrund der Anwesenheit von Si-H oder Si-O-CH 3 Gruppen sind, können durch nasschemische Behandlung mit Ätzen mit HF-Lösung oder einer Beschichtung mit einem Photoresist 13 erreicht werden-15. Zur selektiven Bereichssteuerung der Benetzbarkeit von Si zu erreichen, sind komplexe Strukturierungsschritte in der Regel erforderlich, einschließlich der Behandlung in chemischen Lösungen 16. Die hohe chemische Reaktivität von UV-Laserstrahlung hat auch zu selektiven Bereich Prozess organischen Film beschichteten festen Substrate verwendet wurden und ihre Benetzbarkeit 17 ändern. Jedoch ist eine begrenzte Menge von Daten über die lasergestützte Modifikation Si Benetzbarkeit durch Bestrahlung von Proben in verschiedenen chemischen Lösungen getaucht erhältlich. In unserem früheren Forschung wurde UV-Laser-Bestrahlung von III-V-Halbleiter in Luft 18-20 und NH 3 21 erfolgreich verwendet, um die chemische Oberflächenzusammensetzung GaAs, InGaAs und InP verändern. Wir haben festgestellt, dass die UV-Laserbestrahlung von III-V-Halbleitern in deionisiertem (DI) Wasser senkt die Oberflächenoxide und Carbide, während das Wasser auf Halbleiteroberfläche adsorbiert erhöht 22. Ein stark hydrophoben Si-Oberfläche (CA ~ 103 °) wurde durch ArF Laserbestrahlung von Si-Proben in Methanol bei unseren letzten Arbeiten 23 erhalten. Wie durch Röntgenphotoelektronenspektroskopie (XPS) zeigte, ist dies vor allem auf die Fähigkeit des ArF-Lasers, um CH 3 OH photodissociate. Wir haben auch KrF- und ArF-Lasern auf Si (001) in einer 0,01% igen H 2 O 2 in DI-Wasser zu bestrahlen. Dies erlaubte uns, Selektives Bildung von superhydrophilen Oberfläche des Si (001), gekennzeichnet durch die CA in der Nähe der 15 ° erzielen. Die XPS-Ergebnisse legen nahe, dass diese aufgrund der Erzeugung von Si-OH-Bindungen auf der bestrahlten Oberfläche 24 ist. Eine detaillierte Beschreibung dieser neuen Technik mit KrF- und ArF-Lasern zur selektiven Bereich in situ Modifizierung der hydrophilen / hydrophoben Oberfläche der Si-Oberfläche in geringer Konzentration von H 2 O 2 / H 2 O und Methanol-Lösungen wird in diesem Artikel gezeigt. Die hier gemachten Angaben sollten ausreichendamit ähnliche Experimente, die von interessierten Forschern durchgeführt werden.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>fluorescein stained nanospheres</td>
			<td>Invitrogen</td>
			<td>F8795</td>
			<td></td>
		</tr>
		<tr>
			<td>OptiClear</td>
			<td>National Diagnostics</td>
			<td>OE-101</td>
			<td></td>
		</tr>
		<tr>
			<td>ArF laser (&#955;=193 nm)</td>
			<td>Lumonics</td>
			<td>pulse master 800</td>
			<td></td>
		</tr>
		<tr>
			<td>KrF laser (&#955;=248 nm)</td>
			<td>Lumonics</td>
			<td>pulse master 800</td>
			<td></td>
		</tr>
		<tr>
			<td>XPS</td>
			<td>Kratos Analytical</td>
			<td>AXIS Ultra DLD</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescence microscope</td>
			<td>Olympus</td>
			<td>IX71</td>
			<td></td>
		</tr>
		<tr>
			<td>XPS quantitification software</td>
			<td>CasaXPS</td>
			<td>2.3.15</td>
			<td></td>
		</tr>
	</tbody>
</table>

selective area modification of silicon surface wettability by pulsed uv laser irradiation in liquid environment

Die Benetzbarkeit von Silizium (Si) ist einer der wichtigsten Parameter bei der Technologie der Oberflächen Funktionalisierung dieses Materials und Herstellung von Biosensor-Geräten. Wir berichten über ein Protokoll mit KrF- und ArF-Laser bestrahlt Si (001) Proben in einer flüssigen Umgebung mit geringer Anzahl von Impulsen eingetaucht ist und bei mäßig niedrigen Impuls Fluenzen Si Benetzbarkeit Modifizierung zu induzieren. Wafer für bis zu 4 h eingetaucht in 0,01% H 2 O 2 / H 2 O Lösung nicht messbare Veränderung ihrer Anfangskontaktwinkel (CA) ~ 75 ° zu zeigen. Jedoch die 500-Puls-KrF- und ArF-Laser-Bestrahlung eines solchen Wafer in einer Mikrokammer mit 0,01% H gefüllt 2 O 2 / H 2 O-Lösung bei 250 und 65 mJ / cm 2 sind, hat die CA nahe 15 ° verringert wird, was die Bildung einer superhydrophile Oberfläche. Die Bildung von OH-terminierten Si (001), ohne messbare Veränderung der Waferoberflächenmorphologie besitztwurde durch Röntgenphotoelektronenspektroskopie und Rasterkraftmikroskopie-Messungen bestätigt. Die selektive Bereichs bestrahlten Proben wurden dann in einem biotinkonjugierten Fluorescein gefärbten Nanosphären Lösung für 2 Stunden eingetaucht, was zu einer erfolgreichen Immobilisierung von Nanokugeln in dem nicht-bestrahlten Bereich. Dies zeigt das Potential des Verfahrens zur selektiven Bereichs Biofunktionalisierung und Herstellung von fortschrittlichen Si-basierten Biosensor-Architekturen. Wir, die bei Impuls Fluenz von 65 mJ beschreiben auch ein ähnliches Protokoll der Bestrahlung von Wafern in Methanol (CH 3 OH) eingetaucht, mit einem ArF-Laser / cm 2 und in situ-Bildung eines stark hydrophoben Oberfläche von Si (001) mit dem CA-103 °. Die XPS-Ergebnisse zeigen, ArF Laser induzierte Bildung von Si (OCH 3) x Verbindungen verantwortlich für die beobachtete Hydrophobizität. Es wurden jedoch keine solchen Verbindungen, die durch XPS der Si-Oberfläche durch KrF-Laser in Methanol bestrahlt gefunden, was zeigt,die Unfähigkeit der KrF-Laser, um Methanol photodissociate und schaffen -OCH 3 Reste.

Diese repräsentative Ergebnisse haben in unseren bisherigen Veröffentlichungen 23,24 präsentiert. Abbildung 1 zeigt die CA vs. N (Anzahl der Impulse) auf Websites von KrF-Laser bei 250 mJ / cm 2 bestrahlt in DI H 2 O für verschiedene Konzentrationen von H 2 O 2 / H 2 O-Lösungen (z. B. 0,01, 0,02, 0,05 und 0,2%). Die CA nimmt mit zunehmender Impulszahl für die gesamte H 2 O 2 -Lösungen. Die minimale CA (~ 15 °) für die 0,...

Watch this Scientific Journal Video about Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment at JoVE.com

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

Wir berichten von einem Verfahren der in situ Veränderung der HF behandelt Si (001) -Oberfläche in einer hydrophilen oder hydrophoben Zustand durch Bestrahlen Proben in Mikrofluidkammern mit H 2 O 2 / H 2 O-Lösung (0,01% -0,5%) oder Methanol-Lösungen gefüllt mittels gepulster UV-Laser mit einer relativen niedrigen Impulsfluenz.

Selektive Bereichsänderung des Siliziumoberfläche Benetzbarkeit durch gepulste UV-Laser-Bestrahlung in flüssigen Umgebung

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

selective-area-modification-silicon-surface-wettability-pulsed-uv

Research

JoVE Journal

Engineering

8.2K Aufrufe.  Université de Sherbrooke.  Wir berichten von einem Verfahren der in situ Veränderung der HF behandelt Si (001) -Oberfläche in einer hydrophilen oder hydrophoben Zustand durch Bestrahlen Proben in Mikrofluidkammern mit H 2 O 2 / H 2 O-Lösung (0,01% -0,5%) oder Methanol-Lösungen gefüllt mittels gepulster UV-Laser mit einer relativen niedrigen Impulsfluenz. 

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

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11.
Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps).
Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators.

An experimental method to examine the early plasma evolution induced by ultrashort laser pulses is described. Using this method, high quality images of early plasma are obtained with high temporal and spatial resolutions. A novel integrated atomistic model is used to simulate and explain the mechanisms of early plasma.

Untersuchung der frühen Evolution von Plasma ultrakurzer Laserpulse

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a ...

Forschung

Ingenieurwesen

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.
In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.
Specifically, we will discuss:
<ol class="lroman">
	<li>Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.</li>
	<li>Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.</li>
	<li>Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.</li>
</ol>
Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained.

White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

Charakterisierung von Oberflächenmodifikationen mittels Weißlicht-Interferometrie: Anwendungen in der Ion Sputtern, Laserablation, und Tribologie Experimente

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. ...

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Herstellung von transparenten leitenden Oxide durch Pulsed Laser Deposition Nano-engineered

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

Visualisierung von High-Speed-Flüssigkeitsstrahl-Impaction auf einer sich bewegenden Oberfläche

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

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.

Integration of Light Trapping Silber-Nanostrukturen in Hydrogenated Microcrystalline Silicon Solar Cells durch Transferdruck

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

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

Automatisierung der Modenkopplung in einem nicht-linearen Polarisationsdrehung Faserlaser durch Ausgabe Polarisationsmessungen

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Emissionsspektroskopische Grenzschichtuntersuchung während ablative Materialprüfung in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

Hochtemperatur Herstellung von Nanostrukturierte Yttrium-stabilisiertes Zirkonoxid (YSZ) Scaffolds durch<em&gt; In Situ</em&gt; Carbon-Templating Xerogele

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

Vorbereitung der Flüssigkristall-Netzwerke für makroskopische oszillierende Bewegung, die durch Licht induzierten

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves several steps, include drawing samples, cooling, cutting, transport to the laboratory, and analysis. The whole analysis process requires more than 30 minutes, which hinders on-line process control. Laser-induced breakdown spectroscopy is an excellent on-line analysis method that can satisfy the requirements of vacuum induction melting because it is fast and noncontact and does not require sample preparation. The experimental facility uses a lamp-pumped Q-switched laser to ablate melted liquid steel with an output energy of 80 mJ, a frequency of 5 Hz, a FWHM pulse width of 20 ns, and a working wavelength of 1,064 nm. A multi-channel linear charge coupled device (CCD) spectrometer is used to measure the emission spectrum in real time, with a spectral range from 190 to 600 nm and a resolution of 0.06 nm at a wavelength of 200 nm. The protocol includes several steps: standard alloy sample preparation and an ingredient test, smelting of standard samples and determination of the laser breakdown spectrum, and construction of the elements concentration quantitative analysis curve of each element. To realize the concentration analysis of unknown samples, the spectrum of a sample also needs to be measured and disposed with the same process. The composition of all main elements in the melted alloy can be quantitatively analyzed with an internal standard method. The calibration curve shows that the limit of detection of most metal elements ranges from 20-250 ppm. The concentration of elements, such as Ti, Mo, Nb, V, and Cu, can be lower than 100 ppm, and the concentrations of Cr, Al, Co, Fe, Mn, C, and Si range from 100-200 ppm. The R2 of some calibration curves can exceed 0.94.

During vacuum induction melting, laser-induced breakdown spectroscopy is used to perform real-time quantitative analysis of the main-ingredient elements of a molten alloy.

Quantitative Analyse der Vakuum-Induktionsschmelze durch Laser-induzierte Spectroskopie

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves ...