Name: preparation of macroporous epitaxial quartz films on silicon by chemical solution deposition
Uploaded: 2015-12-21T15:00:00.000+00:00
Duration: 7 min 37 s
Description: Watch this Scientific Journal Video about Preparation of Macroporous Epitaxial Quartz Films on Silicon by Chemical Solution Deposition at JoVE.com

Diese Arbeit wurde teilweise durch eine PEPS Projekt der Cellule Energie INSIS-CNRS (1D-RENOX) bis ACG und der spanischen Regierung (MAT2012-35324 und PIE-201460I004) finanziert.

1. Herstellung des Sol <ol><li> Es wird eine Lösung von vorhydrolysierter Tetraethylorthosilikat (TEOS) am Tag vor der Herstellung der Gel-Filme in einer Abzugshaube, in dem eine Laborwaage und einem Magnetrührer platziert werden. In diesem Schritt und in der Protokolllaborkittel, Schutzhandschuhe und Schutzbrille tragen. <ol><li> In einem 50 ml Becherglas mit einem Teflon beschichteten Magnetrührstab wiegt 1,68 g CTAB, fügen 48,13 ml Ethanol und 3,00 ml HCl 35%, decken das Becherglas mit einem Uhrglas und rühren, bis die CTAB vollständig gelöst ist. </li><li> In 7,37 ml TEOS zu dem Becherglas tropfenweise (mit einer Geschwindigkeit von ca. 1-2 Tropfen pro Sekunde) unter Rühren, decken Sie den Kolben, der mit einem Uhrglas und lassen Sie es rühren O / N. </li></ol></li><li> Am nächsten Tag, bereiten eine 1 M wässrige Lösung von Sr 2+. Führen Sie dieses und die folgenden Schritte kurz vor der Herstellung der Gel-Filme, weil eine gealterte Lösung ist anfällig für Re-Fällung des Sr-Salz. <ol><li> Wiegen 6.6654 g SrCl 2 · 6H 2 O in einen 25 ml-Meßkolben. </li><li> In hochreinem Wasser (zB Milli-Q) bis zu 25 ml (Meniskus Tangente an den Kolben Marke) und den Kolben mit einer Kunststoffkappe und der Kolben, um das Strontiumchlorid aufzulösen schütteln. </li></ol></li><li> 2 ml der 1 M wässrigen Lösung von Sr 2+ zu dem 50 ml Becherglas mit dem Sol, das übrig war Rühren O / N. Rühren Sie die Lösung für 25 min. </li><li> Entsorgen Sie die Rückstände, die schließlich nach den Sicherheits- und Umweltschutz-Protokolle aus dem Labor erzeugt wurden. </li></ol> 2. Gel-Film Deposition on Si (100) Substrate <ol><li> Herstellung der Substrate <ol><li> Geschnitten Si Platten von etwa 2 cm bis 5 cm aus einem 2-Zoll-p-leitenden (100) Siliziumwafer mit einer Dicke von 200 um durch Spalten des Wafers in einer Richtung parallel oder senkrecht zu der Scheibenfläche unter Verwendung einer Diamantspitze oder ein scharfkantigen Gegenstand. Führen Sie diesen Schritt in Ad-Vance, zum Beispiel am Tag vor der Aufbringung der Gel-Filme. </li><li> Kurz vor der Abscheidung der Gele, reinigen Sie die Substrate mit Ethanol und trocknen lassen oder mit einem Stickstoffstrom oder Druckluft, um das Trocknen zu beschleunigen. Dieser Schritt beim Warten auf den Abschluß des Schritts 1.3. </li></ol></li><li> Coat die Filme. Um eine homogene Makroporenstruktur zu erhalten führen Sie diesen Schritt unter den Bedingungen einer relativen Luftfeuchtigkeit zwischen 20% und 55% bei RT. <ol><li> Stellen Sie eine Tauchbeschichtungsfolge. Wählen der ersten und letzten Positionen unter Berücksichtigung der tatsächlichen Länge des Si-Platte und die Höhe der Lösung in dem Becher, so daß die Platte wenigstens 2 cm oberhalb der Lösungspegel in der Startposition und 1 cm über dem Boden des Becherglas am Ende des Tauch. Stellen Sie sowohl die Immersion und Abzugsgeschwindigkeiten bis 150 mm / min. Stellen Sie die Tauchzeit (Zeit in der Endposition) auf Null. </li><li> Nach Abschluss von Schritt 1.3 wird das Becherglas mit dem sosung in einer gut zentrierten Position unterhalb des Si Bramme aus dem Tauchbeschichtungsvorrichtung Arm hängt. </li><li> Fix eine Ende des Si Platte mit dem Tauchbeschichtungsvorrichtung Arm mit der Klammer, wodurch die Platte möglichst senkrecht in Bezug auf die Horizontale. </li><li> Führen Sie den Tauchbeschichtungssequenz und ausclipsen Si Bramme aus dem Tauchbeschichtungsvorrichtung Arm. Wiederholen Sie die Schritte 2.2.3 und 2.2.4 mit zusätzlichen Si Platten, mehr Filme zu produzieren, kümmert sich nicht um diese Präparate über 1 Stunde zu verlängern, um sicherzustellen, dass die Stabilität der Lösung nicht beeinträchtigt wird. </li></ol></li><li> Entsorgen Sie die Lösungen, die schließlich nach den Sicherheits- und Umweltschutz-Protokolle aus dem Labor erzeugt wurden. </li></ol> 3. Gelfilm Kristallisation durch Wärmebehandlung <ol><li> Thermische Behandlung der Gel-Filme auf Si (100). <ol><li> Von RT bei 3 ° C / min Erhitzen auf 1.000 ° C, Halten bei 1.000 °: Programm einen Ofen, um die folgende Wärmebehandlung in Luftatmosphäre durchführenC für 5 Stunden und Abkühlen auf RT bei 3 ° C / min. </li><li> Platzieren Sie die tauchbeschichtet Si-Substraten in einem Schiffchen aus Aluminiumoxid, führen sie in den Ofen und Ausführen der Wärmebehandlung. </li></ol></li><li> Reinigung der kristallisierten Filme. <ol><li> Tauchen Sie die kristallisierte Filme für 3 Stunden in konzentrierter HNO 3, um die Ansammlungen von Sr 2+, die während der Kristallisation zu der Filmoberfläche ausgestoßen worden sind, zu entfernen, und dann Spülen der Filme zunächst mit entionisiertem Wasser und dann mit Ethanol. </li></ol></li></ol>

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Die Autoren haben nichts zu offenbaren.

Das vorgestellte Verfahren ist ein Bottom-up-Ansatz für makroporöse Quarzfilme auf Si zu erzeugen. Im Vergleich zu dem Standardverfahren der Herstellung von Quarz-Folien, eine Top-Down-Technik auf das Schneiden und Polieren von großen hydrothermisch gezüchtete Kristalle, die in dem Protokoll beschriebene Verfahren erlaubt den Erhalt viel dünnere Folien mit Dicken zwischen 150 und 450 nm, die mit der gesteuert werden kann auf der Basis Entnahmeleistung. Alle experimentellen Einzelheiten in Bezug auf die Kontrolle de...

Wenn ein piezoelektrisches Material, wie α-Quarz mit einer Vorspannung abgegeben wird es einer mechanischen Verformung. Wenn dieses Material porös ist, können diese Volumenänderungen zu Poren Expansion oder Kontraktion führen, die Schaffung eines ansprechenden Systems ähnlich dem, was in lebenden biologischen Organellen zu beachten. 1 verformbare poröse α-Quarz wurde unter Verwendung von Mikro, 2 produziert, aber diese Techniken noch nicht erzeugen 3D-Porenstrukturen, und der Porendurchmesser in der Größenordnung von mehreren hundert Nanometern. Kristallisation von strukturierten amorphen Kieselsäure durch inhomogene Keimbildung durch eine hohe Oberflächenenergien und architektonischen Verformung aufgrund der Vergröberung und Schmelzen verursacht behindert. Außerdem, da alle Formen von Siliciumdioxid sind auf äußerst stabile SiO 4 Tetraeder-Netzwerke errichtet, die freie Energie der Bildung von amorphem Siliziumdioxid, α-Quarz und andere SiO2-Modifikationen in einem weiten Bereich von Temperaturen, Makin nahezu gleich sindg es schwierig, α-Quarz als ein einziges Polymorphs aus der Kristallisation eines amorphen Kieselgel herzustellen. 3 ein weiterer Aspekt, schwieriger macht die kontrollierte Kristallisation von strukturierten amorphen Siliciumdioxids ist, dass Quarz stellt eine relativ langsame Keimbildungsgeschwindigkeit jedoch ein extrem schnelles Wachstum, zwischen 10-94 nm berichtet / sec. 4,5 Langsame Keimbildung in Verbindung mit schnellem Wachstum neigt Kristalle viel größer als die ursprüngliche nanoporöse Struktur, wodurch das ursprüngliche Morphologie verloren zu erzeugen. Alkalimetalle, wie Na + und Li +, verwendet worden, um α-Quarz kristallisieren, häufig in Kombination mit hydrothermaler Behandlung. 5,6 Auch ein Ti 4+ / Ca 2+ Kombination wurde verwendet, um kugelförmige Teilchen von Siliciumdioxid in kristallisieren Quarz durch einen Weg der sanften Chemie unter Verwendung von Silizium-Alkoxide. 7 ist die gesteuerte Kristallisation eines strukturierten amorpher Kieselsäure Film in Quarz blieb jedoch eine Herausforderung. SiO 2 bei Umgebungsdruck und relativ niedrigen Temperaturen zu katalysieren. 8,9 Epitaxy, ergibt sich aus der guten Übereinstimmung zwischen α-Quarz und der &lt;100&gt; Silizium-Substrat, Herstellung von orientierten piezoelektrischen Dünnfilme. Verdampfen induzierten Selbstorganisation mesoporösen Siliciumdioxid Folien herzustellen wird seit 1999 10 Diese Technik wurde untersucht und auf eine Vielzahl von Matrixmittel unter verschiedenen Bedingungen angelegt, um Poren von variablen Größen und Mesophasen herzustellen. Es wurde gefunden, daß subnanometric Veränderungen Mesoporengröße kann eine dramatische Auswirkung auf solute Diffusion durch poröse Systeme 11 aufweisen, Validierung dieser große Aufmerksamkeit auf die Struktur Pore. Darüber hinaus kann die Zugänglichkeit zu der internen Kieselsäure Porensystem durch Steuern der mizellaren Phase der Vorlage erhalten werden. 12 Hier wird der Syntheseweg tKappe ermöglicht uneingeschränkte Kontrolle über die Dicke und die Porengröße aus amorphem Siliciumdioxid-Schichten unter Verwendung einer neuen Phasentrennung zeigten. 13 Diese Filme werden mit Sr (II) salze und kristallisiert, um a-Quarz bei 1000 ° C an der Luft bei Umgebungsdruck infiltriert. Die Porengröße zurückhaltbar mit diesen Kristallisationsprozess wird bestimmt, und die Wirkung der Wandstärke und der Filmdicke untersucht. Schließlich die Piezoelektrizität und die Verformbarkeit des Porensystems untersucht.

<table><tbody><tr><td>Dip coater</td><td>Nadetech&amp;nbsp;</td><td>ND-DC 11/150&amp;nbsp;</td><td></td></tr><tr><td>Furnace</td><td>Nabertherm&amp;nbsp;</td><td>R 50/250/12</td><td></td></tr><tr><td>Atomic Force Microscope</td><td>Agilent&amp;nbsp;</td><td>5500 LS</td><td></td></tr><tr><td>Silicon wafers</td><td>SHE Europe Ltd.</td><td></td><td></td></tr><tr><td>SrCl&lt;sub&gt;2&lt;/sub&gt;&amp;middot;6H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Aldrich</td><td>13909</td><td></td></tr><tr><td>CTAB</td><td>Aldrich</td><td>H5582</td><td></td></tr><tr><td>Ethanol Absolute&amp;nbsp;</td><td>Aldrich</td><td>161086</td><td></td></tr><tr><td>HCl 35% solution</td><td>PanReac</td><td>721019</td><td></td></tr><tr><td>TEOS</td><td>Aldrich</td><td>131903</td><td></td></tr></tbody></table>

preparation of macroporous epitaxial quartz films on silicon by chemical solution deposition

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step process based on the preparation of a sol in a one-pot synthesis which is followed by the deposition of a gel film on Si(100) substrates by evaporation induced self-assembly using the dip-coating technique and ends with a thermal treatment of the material to induce the gel crystallization and the growth of the quartz film. The formation of a silica gel is based on the reaction of a tetraethyl orthosilicate and water, catalyzed by HCl, in ethanol. However, the solution contains two additional components that are essential for preparing mesoporous epitaxial quartz films from these silica gels dip-coated on Si. Alkaline earth ions, like Sr2+ act as glass melting agents that facilitate the crystallization of silica and in combination with cetyl trimethylammonium bromide (CTAB) amphiphilic template form a phase separation responsible of the macroporosity of the films. The good matching between the quartz and silicon cell parameters is also essential in the stabilization of quartz over other SiO2 polymorphs and is at the origin of the epitaxial growth.

Das Fortschreiten der Materialsynthese wurde durch Überwachung verschiedener Aspekte gesteuert. Nach dem Tauchbeschichtungsverfahren kann man den Aspekt der Filme, den eventuellen Auftreten von Beugungsstrukturen in dem reflektierten Fleck eines grünen Lasers und der Rasterelektronenmikroskopie (SEM) in Rückstreuelektronen-Modus (1A-B) zu beobachten. Nach dem Kristallisationsverfahren ist es wichtig, die Rasterkraftmikroskopie (AFM) topografische Bilder (1C)</...

Watch this Scientific Journal Video about Preparation of Macroporous Epitaxial Quartz Films on Silicon by Chemical Solution Deposition at JoVE.com

Preparation of Macroporous Epitaxial Quartz Films on Silicon by Chemical Solution Deposition

A protocol is presented for the preparation of piezoelectric macroporous epitaxial films of quartz on silicon by solution chemistry using dip-coating and thermal treatments in air.

Herstellung von makroporösen Epitaxial-Quarz-Films auf Silizium durch Chemical Solution Deposition

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step ...

preparation-macroporous-epitaxial-quartz-films-on-silicon-chemical

Research

JoVE Journal

Chemistry

9.2K Aufrufe.  CNRS-École Centrale de Lyon. A protocol is presented for the preparation of piezoelectric macroporous epitaxial films of quartz on silicon by solution chemistry using dip-coating and thermal treatments in air. 

Serie: Preparation of Macroporous Epitaxial Quartz Films on Silicon by Chemical Solution Deposition

Polycrystalline Silicon Thin-film Solar cells with Plasmonic-enhanced Light-trapping

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To compensate for lower light absorption such physically thin devices have to incorporate light-trapping which increases their optical thickness. Light scattering by textured surfaces is a common technique but it cannot be universally applied to all solar cell technologies. Some cells, for example those made of evaporated silicon, are planar as produced and they require an alternative light-trapping means suitable for planar devices. Metal nanoparticles formed on planar silicon cell surface and capable of light scattering due to surface plasmon resonance is an effective approach.
The paper presents a fabrication procedure of evaporated polycrystalline silicon solar cells with plasmonic light-trapping and demonstrates how the cell quantum efficiency improves due to presence of metal nanoparticles.
To fabricate the cells a film consisting of alternative boron and phosphorous doped silicon layers is deposited on glass substrate by electron beam evaporation. An Initially amorphous film is crystallised and electronic defects are mitigated by annealing and hydrogen passivation. Metal grid contacts are applied to the layers of opposite polarity to extract electricity generated by the cell. Typically, such a ~2 &mu;m thick cell has a short-circuit current density (Jsc) of 14-16 mA/cm2, which can be increased up to 17-18 mA/cm2 (~25% higher) after application of a simple diffuse back reflector made of a white paint.
To implement plasmonic light-trapping a silver nanoparticle array is formed on the metallised cell silicon surface. A precursor silver film is deposited on the cell by thermal evaporation and annealed at 23&deg;C to form silver nanoparticles. Nanoparticle size and coverage, which affect plasmonic light-scattering, can be tuned for enhanced cell performance by varying the precursor film thickness and its annealing conditions. An optimised nanoparticle array alone results in cell Jsc enhancement of about 28%, similar to the effect of the diffuse reflector. The photocurrent can be further increased by coating the nanoparticles by a low refractive index dielectric, like MgF2, and applying the diffused reflector. The complete plasmonic cell structure comprises the polycrystalline silicon film, a silver nanoparticle array, a layer of MgF2, and a diffuse reflector. The Jsc for such cell is 21-23 mA/cm2, up to 45% higher than Jsc of the original cell without light-trapping or ~25% higher than Jsc for the cell with the diffuse reflector only.
Introduction
Light-trapping in silicon solar cells is commonly achieved via light scattering at textured interfaces. Scattered light travels through a cell at oblique angles for a longer distance and when such angles exceed the critical angle at the cell interfaces the light is permanently trapped in the cell by total internal reflection (Animation 1: Light-trapping). Although this scheme works well for most solar cells, there are developing technologies where ultra-thin Si layers are produced planar (e.g. layer-transfer technologies and epitaxial c-Si layers) 1 and or when such layers are not compatible with textures substrates (e.g. evaporated silicon) 2. For such originally planar Si layer alternative light trapping approaches, such as diffuse white paint reflector 3, silicon plasma texturing 4 or high refractive index nanoparticle reflector 5 have been suggested.
Metal nanoparticles can effectively scatter incident light into a higher refractive index material, like silicon, due to the surface plasmon resonance effect 6. They also can be easily formed on the planar silicon cell surface thus offering a light-trapping approach alternative to texturing. For a nanoparticle located at the air-silicon interface the scattered light fraction coupled into silicon exceeds 95% and a large faction of that light is scattered at angles above critical providing nearly ideal light-trapping condition (Animation 2: Plasmons on NP). The resonance can be tuned to the wavelength region, which is most important for a particular cell material and design, by varying the nanoparticle average size, surface coverage and local dielectric environment 6,7. Theoretical design principles of plasmonic nanoparticle solar cells have been suggested 8. In practice, Ag nanoparticle array is an ideal light-trapping partner for poly-Si thin-film solar cells because most of these design principle are naturally met. The simplest way of forming nanoparticles by thermal annealing of a thin precursor Ag film results in a random array with a relatively wide size and shape distribution, which is particularly suitable for light-trapping because such an array has a wide resonance peak, covering the wavelength range of 700-900 nm, important for poly-Si solar cell performance. The nanoparticle array can only be located on the rear poly-Si cell surface thus avoiding destructive interference between incident and scattered light which occurs for front-located nanoparticles 9. Moreover, poly-Si thin-film cells do not requires a passivating layer and the flat base-shaped nanoparticles (that naturally result from thermal annealing of a metal film) can be directly placed on silicon further increases plasmonic scattering efficiency due to surface plasmon-polariton resonance 10.
The cell with the plasmonic nanoparticle array as described above can have a photocurrent about 28% higher than the original cell. However, the array still transmits a significant amount of light which escapes through the rear of the cell and does not contribute into the current. This loss can be mitigated by adding a rear reflector to allow catching transmitted light and re-directing it back to the cell. Providing sufficient distance between the reflector and the nanoparticles (a few hundred nanometers) the reflected light will then experience one more plasmonic scattering event while passing through the nanoparticle array on re-entering the cell and the reflector itself can be made diffuse - both effects further facilitating light scattering and hence light-trapping. Importantly, the Ag nanoparticles have to be encapsulated with an inert and low refractive index dielectric, like MgF2 or SiO2, from the rear reflector to avoid mechanical and chemical damage 7. Low refractive index for this cladding layer is required to maintain a high coupling fraction into silicon and larger scattering angles, which are ensured by the high optical contrast between the media on both sides of the nanoparticle, silicon and dielectric 6. The photocurrent of the plasmonic cell with the diffuse rear reflector can be up to 45% higher than the current of the original cell or up to 25% higher than the current of an equivalent cell with the diffuse reflector only.

Polycrystalline silicon thin-film solar cells on glass are fabricated by deposition of boron and phosphorous doped silicon layers followed by crystallisation, defect passivation and metallisation. Plasmonic light-trapping is introduced by forming Ag nanoparticles on the silicon cell surface capped with a diffused reflector resulting in ~45% photocurrent enhancement.

Polykristalline Silizium-Dünnschicht-Solarzellen mit Plasmonische-enhanced Light-Trapping

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To ...

Forschung

Ingenieurwesen

Fabrication of Silica Ultra High Quality Factor Microresonators

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the quality factor (Q) of the cavity, can be in excess of 500ns for cavities with Q factors above 100 million. As a result of their low material losses, silica microcavities have demonstrated some of the longest photon lifetimes to date1-2. Since a portion of the circulating light extends outside the resonator, these devices can also be used to probe the surroundings. This interaction has enabled numerous experiments in biology, such as single molecule biodetection and antibody-antigen kinetics, as well as discoveries in other fields, such as development of ultra-low-threshold microlasers, characterization of thin films, and cavity quantum electrodynamics studies.3-7
The two primary silica resonant cavity geometries are the microsphere and the microtoroid. Both devices rely on a carbon dioxide laser reflow step to achieve their ultra-high-Q factors (Q&gt;100 million).1-2,8-9 However, there are several notable differences between the two structures. Silica microspheres are free-standing, supported by a single optical fiber, whereas silica microtoroids can be fabricated on a silicon wafer in large arrays using a combination of lithography and etching steps. These differences influence which device is optimal for a given experiment.
Here, we present detailed fabrication protocols for both types of resonant cavities. While the fabrication of microsphere resonant cavities is fairly straightforward, the fabrication of microtoroid resonant cavities requires additional specialized equipment and facilities (cleanroom). Therefore, this additional requirement may also influence which device is selected for a given experiment.
Introduction
An optical resonator efficiently confines light at specific wavelengths, known as the resonant wavelengths of the device. 1-2 The common figure of merit for these optical resonators is the quality factor or Q. This term describes the photon lifetime (&tau;o) within the resonator, which is directly related to the resonator's optical losses. Therefore, an optical resonator with a high Q factor has low optical losses, long photon lifetimes, and very low photon decay rates (1/&tau;o). As a result of the long photon lifetimes, it is possible to build-up extremely large circulating optical field intensities in these devices. This very unique property has allowed these devices to be used as laser sources and integrated biosensors.10
A unique sub-class of resonators is the whispering gallery mode optical microcavity. In these devices, the light is confined in circular orbits at the periphery. Therefore, the field is not completely confined within the device, but evanesces into the environment. Whispering gallery mode optical cavities have demonstrated some of the highest quality factors of any optical resonant cavity to date.9,11 Therefore, these devices are used throughout science and engineering, including in fundamental physics studies and in telecommunications as well as in biodetection experiments. 3-7,12
Optical microcavities can be fabricated from a wide range of materials and in a wide variety of geometries. A few examples include silica and silicon microtoroids, silicon, silicon nitride, and silica microdisks, micropillars, and silica and polymer microrings.13-17 The range in quality factor (Q) varies as dramatically as the geometry. Although both geometry and high Q are important considerations in any field, in many applications, there is far greater leverage in boosting device performance through Q enhancement. Among the numerous options detailed previously, the silica microsphere and the silica microtoroid resonator have achieved some of the highest Q factors to date.1,9 Additionally, as a result of the extremely low optical loss of silica from the visible through the near-IR, both microspheres and microtoroids are able to maintain their Q factors over a wide range of testing wavelengths.18 Finally, because silica is inherently biocompatible, it is routinely used in biodetection experiments.
In addition to high material absorption, there are several other potential loss mechanisms, including surface roughness, radiation loss, and contamination loss.2 Through an optimization of the device size, it is possible to eliminate radiation losses, which arise from poor optical field confinement within the device. Similarly, by storing a device in an appropriately clean environment, contamination of the surface can be minimized. Therefore, in addition to material loss, surface scattering is the primary loss mechanism of concern.2,8
In silica devices, surface scattering is minimized by using a laser reflow technique, which melts the silica through surface tension induced reflow. While spherical optical resonators have been studied for many years, it is only with recent advances in fabrication technologies that researchers been able to fabricate high quality silica optical toroidal microresonators (Q&gt;100 million) on a silicon substrate, thus paving the way for integration with microfluidics.1
The present series of protocols details how to fabricate both silica microsphere and microtoroid resonant cavities. While silica microsphere resonant cavities are well-established, microtoroid resonant cavities were only recently invented.1 As many of the fundamental methods used to fabricate the microsphere are also used in the more complex microtoroid fabrication procedure, by including both in a single protocol it will enable researchers to more easily trouble-shoot their experiments.

We describe the use of a carbon dioxide laser reflow technique to fabricate silica resonant cavities, including free-standing microspheres and on-chip microtoroids. The reflow method removes surface imperfections, allowing long photon lifetimes within both devices. The resulting devices have ultra high quality factors, enabling applications ranging from telecommunications to biodetection.

Herstellung von Silica Ultra High Quality Factor Mikroresonatoren

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the ...

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

Atomar definierte Vorlagen Epitaxieausrüstung komplexer Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

Chemie

Soft Lithographic Functionalization and Patterning Oxide-free Silicon and Germanium

The development of hybrid electronic devices relies in large part on the integration of (bio)organic materials and inorganic semiconductors through a stable interface that permits efficient electron transport and protects underlying substrates from oxidative degradation. Group IV semiconductors can be effectively protected with highly-ordered self-assembled monolayers (SAMs) composed of simple alkyl chains that act as impervious barriers to both organic and aqueous solutions. Simple alkyl SAMs, however, are inert and not amenable to traditional patterning techniques. The motivation for immobilizing organic molecular systems on semiconductors is to impart new functionality to the surface that can provide optical, electronic, and mechanical function, as well as chemical and biological activity. 
Microcontact printing (&mu;CP) is a soft-lithographic technique for patterning SAMs on myriad surfaces.1-9 Despite its simplicity and versatility, the approach has been largely limited to noble metal surfaces and has not been well developed for pattern transfer to technologically important substrates such as oxide-free silicon and germanium. Furthermore, because this technique relies on the ink diffusion to transfer pattern from the elastomer to substrate, the resolution of such traditional printing is essentially limited to near 1 &mu;m.10-16
In contrast to traditional printing, inkless &mu;CP patterning relies on a specific reaction between a surface-immobilized substrate and a stamp-bound catalyst. Because the technique does not rely on diffusive SAM formation, it significantly expands the diversity of patternable surfaces. In addition, the inkless technique obviates the feature size limitations imposed by molecular diffusion, facilitating replication of very small (&lt;200 nm) features.17-23 However, up till now, inkless &mu;CP has been mainly used for patterning relatively disordered molecular systems, which do not protect underlying surfaces from degradation.
Here, we report a simple, reliable high-throughput method for patterning passivated silicon and germanium with reactive organic monolayers and demonstrate selective functionalization of the patterned substrates with both small molecules and proteins. The technique utilizes a preformed NHS-reactive bilayered system on oxide-free silicon and germanium. The NHS moiety is hydrolyzed in a pattern-specific manner with a sulfonic acid-modified acrylate stamp to produce chemically distinct patterns of NHS-activated and free carboxylic acids. A significant limitation to the resolution of many &mu;CP techniques is the use of PDMS material which lacks the mechanical rigidity necessary for high fidelity transfer. To alleviate this limitation we utilized a polyurethane acrylate polymer, a relatively rigid material that can be easily functionalized with different organic moieties. Our patterning approach completely protects both silicon and germanium from chemical oxidation, provides precise control over the shape and size of the patterned features, and gives ready access to chemically discriminated patterns that can be further functionalized with both organic and biological molecules. The approach is general and applicable to other technologically-relevant surfaces.

Here we describe a simple method for patterning oxide-free silicon and germanium with reactive organic monolayers and demonstrate functionalization of the patterned substrates with small molecules and proteins. The approach completely protects surfaces from chemical oxidation, provides precise control over feature morphology, and provides ready access to chemically discriminated patterns.

Soft-Lithographie Funktionalisierung und Strukturierung Oxydfreie Silizium und Germanium

The development of hybrid electronic devices relies in large part on the integration of (bio)organic materials and inorganic semiconductors through a ...

Biotechnik

Fabrication of Large-area Free-standing Ultrathin Polymer Films

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films. Typically, ultrathin films are prepared using either sacrificial layers, which may damage the film or affect its mechanical properties, or they are made on freshly cleaved mica, a substrate that is difficult to scale. Further, the size of ultrathin film is typically limited to a few square millimeters. In this method, we modify a surface with a polyelectrolyte that alters the strength of adhesion between polymer and deposition substrate. The polyelectrolyte can be shown to remain on the wafer using spectroscopy, and a treated wafer can be used to produce multiple films, indicating that at best minimal amounts of the polyelectrolyte are added to the film. The process has thus far been shown to be limited in scalability only by the size of the coating equipment, and is expected to be readily scalable to industrial processes. In this study, the protocol for making the solutions, preparing the deposition surface, and producing the films is described.

We describe a method for the fabrication of large-area (up to 13 cm diameter) and ultrathin (as thin as 8 nm) polymer films. Instead of using a sacrificial interlayer to delaminate the film from its substrate, we use a self-limiting surface treatment suitable for arbitrarily large areas.

Herstellung von großflächigen Freistehende ultradünne Polymerfilme

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films.  Typically, ultrathin films are prepared ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

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

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

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

Eine neuartige Methode für<em&gt; In Situ</em&gt; Elektromechanische Charakterisierung von nanoskaligen Proben

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

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

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

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

Herstellung von ultra-dünnen Farbfilm mit stark absorbierenden Medien mit schrägen Winkel Deposition

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

Fabricating Reactive Surfaces with Brush-like and Crosslinked Films of Azlactone-Functionalized Block Co-Polymers

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl dimethyl azlactone) (PGMA-b-PVDMA), are presented. Due to the high reactivity of azlactone groups towards amine, thiol, and hydroxyl groups, PGMA-b-PVDMA surfaces can be modified with secondary molecules to create chemically or biologically functionalized interfaces for a variety of applications. Previous reports of patterned PGMA-b-PVDMA interfaces have used traditional top-down patterning techniques that generate non-uniform films and poorly controlled background chemistries. Here, we describe customized patterning techniques that enable precise deposition of highly uniform PGMA-b-PVDMA films in backgrounds that are chemically inert or that have biomolecule-repellent properties. Importantly, these methods are designed to deposit PGMA-b-PVDMA films in a manner that completely preserves azlactone functionality through each processing step. Patterned films show well-controlled thicknesses that correspond to polymer brushes (~90 nm) or to highly crosslinked structures (~1-10 &#956;m). Brush patterns are generated using either the parylene lift-off or interface directed assembly methods described and are useful for precise modulation of overall chemical surface reactivity by adjusting either the PGMA-b-PVDMA pattern density or the length of the VDMA block. In contrast, the thick, crosslinked PGMA-b-PVDMA patterns are obtained using a customized micro-contact printing technique and offer the benefit of higher loading or capture of secondary material due to higher surface area to volume ratios. Detailed experimental steps, critical film characterizations, and trouble-shooting guides for each fabrication method are discussed.

Surface fabrication methods for patterned deposition of nanometer thick brushes or micron thick, crosslinked films of an azlactone block co-polymer are reported. Critical experimental steps, representative results, and limitations of each method are discussed. These methods are useful for creating functional interfaces with tailored physical features and tunable surface reactivity.

Herstellung von reaktiven Oberflächen mit Pinsel-Like und querverbunden Filme von Azlactone funktionalisiert Block-Copolymere

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl ...

Theoretical Calculation and Experimental Verification for Dislocation Reduction in Germanium Epitaxial Layers with Semicylindrical Voids on Silicon

Reduction of threading dislocation density (TDD) in epitaxial germanium (Ge) on silicon (Si) has been one of the most important challenges for the realization of monolithically integrated photonics circuits. The present paper describes methods of theoretical calculation and experimental verification of a novel model for the reduction of TDD. The method of theoretical calculation describes the bending of threading dislocations (TDs) based on the interaction of TDs and non-planar growth surfaces of selective epitaxial growth (SEG) in terms of dislocation image force. The calculation reveals that the presence of voids on SiO2 masks help to reduce TDD. Experimental verification is described by germanium (Ge) SEG, using an ultra-high vacuum chemical vapor deposition method and TD observations of the grown Ge via etching and cross-sectional transmission electron microscope (TEM). It is strongly suggested that the TDD reduction would be due to the presence of semicylindrical voids over the SiO2 SEG masks and growth temperature. For experimental verification, epitaxial Ge layers with semicylindrical voids are formed as the result of SEG of Ge layers and their coalescence. The experimentally obtained TDDs reproduce the calculated TDDs based on the theoretical model. Cross-sectional TEM observations reveal that both the termination and generation of TDs occur at semicylindrical voids. Plan-view TEM observations reveal a unique behavior of TDs in Ge with semicylindrical voids (i.e., TDs are bent to be parallel to the SEG masks and the Si substrate).

Theoretical calculation and experimental verification are proposed for a reduction of threading dislocation (TD) density in germanium epitaxial layers with semicylindrical voids on silicon. Calculations based on the interaction of TDs and surface via image force, TD measurements, and transmission electron microscope observations of TDs are presented.

Theoretische Berechnung und experimenteller Nachweis zur Versetzungsreduktion in Germanium-Epitaxieschichten mit semizylindrischen Hohlräumen auf Silizium

Reduction of threading dislocation density (TDD) in epitaxial germanium (Ge) on silicon (Si) has been one of the most important challenges for the ...

Epitaxial Nanostructured &alpha;-Quartz Films on Silicon: From the Material to New Devices

In this work, we show a detailed engineering route of the first piezoelectric nanostructured epitaxial quartz-based microcantilever. We will explain all the steps in the process starting from the material to the device fabrication. The epitaxial growth of &#945;-quartz film on SOI (100) substrate starts with the preparation of a strontium doped silica sol-gel and continues with the deposition of this gel into the SOI substrate in a thin film form using the dip-coating technique under atmospheric conditions at room temperature. Before crystallization of the gel film, nanostructuration is performed onto the film surface by nanoimprint lithography (NIL). Epitaxial film growth is reached at 1000 &#176;C, inducing a perfect crystallization of the patterned gel film. Fabrication of quartz crystal cantilever devices is a four-step process based on microfabrication techniques. The process starts with shaping the quartz surface, and then metal deposition for electrodes follows it. After removing the silicone, the cantilever is released from SOI substrate eliminating SiO2 between silicon and quartz. The device performance is analyzed by non-contact laser vibrometer (LDV) and atomic force microscopy (AFM). Among the different cantilever&#8217;s dimensions included in the fabricated chip, the nanostructured cantilever analyzed in this work exhibited a dimension of 40 &#181;m large and 100 &#181;m long and was fabricated with a 600 nm thick patterned quartz layer (nanopillar diameter and separation distance of 400 nm and 1 &#181;m, respectively) epitaxially grown on a 2 &#181;m thick Si device layer. The&#160;measured&#160;resonance frequency was&#160;267 kHz and the estimated quality factor, Q, of the whole mechanical structure was Q ~ 398 under low vacuum conditions. We observed the voltage-dependent linear displacement of cantilever with both techniques (i.e., AFM contact measurement and LDV). Therefore, proving that these devices can be activated through the indirect piezoelectric effect.

Epitaxial Nanostructured &#945;-Quartz Films on Silicon: From the Material to New Devices

This work presents a detailed protocol for the microfabrication of nanostructured &#945;-quartz cantilever on a Silicon-On-Insulator(SOI) technology substrate starting from the epitaxial growth of quartz film with the dip coating method and then nanostructuration of the thin film via nanoimprint lithography.

Epitaxial Nanostructured α-Quartz-Folien auf Silizium: Vom Material zu neuen Geräten

In this work, we show a detailed engineering route of the first piezoelectric nanostructured epitaxial quartz-based microcantilever. We will explain all ...