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

Este trabalho foi parcialmente financiado por um projeto de PEPS Cellule Energie INSIS-CNRS (1D-RENOX) para ACG e pelo Governo espanhol (MAT2012-35324 e PIE-201460I004).

1. Preparação do Sol <ol><li> Prepara-se uma solução de orto-silicato de tetraetilo prehydrolyzed (TEOS) no dia anterior à preparação das películas de gel num exaustor de fumos, em que uma balança de laboratório e um agitador magnético são colocados. Nesta etapa e durante todo o protocolo usar um jaleco, luvas e óculos de segurança. <ol><li> Em um copo de 50 mL contendo uma barra de agitação magnética revestida a Teflon pesar 1,68 g de CTAB, adicionar 48,13 ml de etanol e 3,00 ml de HCl a 35%, cobrir o copo com um vidro de relógio e agita-se até que o CTAB é completamente dissolvido. </li><li> Adicionar 7,37 ml de TEOS, gota a gota ao copo (a uma taxa de cerca de 1-2 gotas por segundo), enquanto se agitava, cobrir o frasco com um vidro de relógio e deixar agitar S / N. </li></ol></li><li> No dia seguinte, preparar uma solução aquosa 1 M de Sr 2+. Executar esta e as seguintes etapas pouco antes da preparação das películas de gel, porque uma solução envelhecida é propenso a re-precipitação do sal Sr. <ol><li> Pesar 6,6654 g de SrCl2 · 6H 2 O em um balão volumétrico de 25 ml. </li><li> Adicionar água ultrapura (por exemplo, Milli-Q) até 25 ml (menisco tangente à marca de balão) e tapar o balão com uma tampa de plástico e agite o frasco para dissolver o cloreto de estrôncio. </li></ol></li><li> Adicionar 2 ml de solução aquosa 1 M de Sr 2+ para a proveta de vidro de 50 ml contendo a solução coloidal que foi deixada em agitação S / N. Agita-se a solução durante 25 min. </li><li> Descarte os resíduos que tenham sido, eventualmente gerados de acordo com os protocolos de segurança e protecção do ambiente de laboratório. </li></ol> 2. Gel película de deposição de Si (100) Substratos <ol><li> Preparação dos substratos <ol><li> Cortar Si lajes de cerca de 2 cm por 5 cm em cada um de 2 polegadas do tipo p (100) da bolacha de silício com uma espessura de 200 micra por clivagem da bolacha numa direcção paralela ou perpendicular ao plano da bolacha usando uma ponta de diamante ou um objeto pérfuro-cortante. Execute esta etapa em anúncioVance, por exemplo, um dia antes da deposição das películas de gel. </li><li> Pouco antes da deposição dos géis, limpar os substratos com etanol e deixar secar ou usar um fluxo de azoto ou ar comprimido para acelerar a secagem. Execute esta etapa enquanto aguarda a conclusão da etapa 1.3. </li></ol></li><li> Brasão dos filmes. A fim de se obter uma estrutura homogénea macroporos executar este passo sob condições de humidade relativa entre 20% e 55%, à TA. <ol><li> Estabelecer uma sequência de revestimento por imersão. Seleccionar as posições iniciais e finais, tendo em conta o comprimento real da laje de Si e o nível da solução no recipiente de forma a que a laje é, pelo menos, 2 cm acima do nível da solução na posição de partida e 1 cm acima do fundo do proveta no final da imersão. Defina ambas as velocidades de imersão e retirada a 150 mm / min. Defina o tempo de imersão (o tempo na posição final) para zero. </li><li> Após a conclusão do passo 1.3 Colocar o copo com a assimlução em uma posição bem centrada abaixo da laje Si pendurado no braço dip-coater. </li><li> Fix uma extremidade da laje de Si ao braço DIP-revestidor com o grampo, assegurando a laje é o mais perpendicular possível em relação à horizontal. </li><li> Execute a sequência de revestimento por imersão e desencaixe a laje Si a partir do braço dip-coater. Repita os passos 2.2.3 e 2.2.4 com lajes Si adicionais para produzir mais filmes, tomando cuidado para não estender esses preparativos para além de 1 h, para assegurar que a estabilidade da solução não seja comprometida. </li></ol></li><li> Descarte as soluções que foram gerados, eventualmente, de acordo com os protocolos de segurança e protecção do ambiente de laboratório. </li></ol> 3. Gel de Cinema de cristalização por tratamento térmico <ol><li> O tratamento térmico das películas de gel de Si (100). <ol><li> Programa de um forno para executar o seguinte tratamento térmico em atmosfera de ar: aquecimento do IR para 1000 ° C a 3 ° C / min, mantendo a 1.000 °; C durante 5 horas e arrefecimento até à TA, a 3 ° C / min. </li><li> Colocar os substratos de Si revestidas por imersão em uma barquinha de alumina, introduzi-la no forno e executar o tratamento térmico. </li></ol></li><li> A limpeza dos filmes cristalizados. <ol><li> Mergulhar os filmes cristalizados durante 3 horas em HNO 3 concentrado a fim de remover as acumulações de Sr 2+ que foram expulsas para a superfície da película durante a cristalização e em seguida enxaguar as películas primeiro com água desionizada e, em seguida, com etanol. </li></ol></li></ol>

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	<li>Esser, A. T., Smith, K. C., Gowrishankar, T. R., Vasilkoski, Z., Weaver, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+for+the+intracellular+manipulation+of+organelles+by+conventional+electroportation.">Mechanisms for the intracellular manipulation of organelles by conventional electroportation.</a> Biophys. J. 98 (11), 2506-2514 (2010).</li><li>Stava, E., Yu, M., Shin, H. C., Shin, H., Kreft, D. J., Blick, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+fabrication+and+piezoelectric+tuning+of+micro-+and+nanopores+in+single+crystal+quartz.">Rapid fabrication and piezoelectric tuning of micro- and nanopores in single crystal quartz.</a> Lab Chip. 13 (1), 156-160 (2013).</li><li>Varshneya, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fundamentals of Inorganic Glasses. , (1994).</li><li>Christov, M., Kirov, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+ratio+of+dissolving+surface+area/growing+surface+area+in+the+hydrothermal+growth+of+quartz.">The ratio of dissolving surface area/growing surface area in the hydrothermal growth of quartz.</a> J. Cryst. Growth. 131 (3-4), 560-564 (1993).</li><li>Bertone, J. F., Cizeron, J., Wahi, R. K., Bosworth, J. K., Colvin, V. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrothermal+synthesis+of+quartz+nanocrystals.">Hydrothermal synthesis of quartz nanocrystals.</a> Nano Lett. 3, 655-659 (2003).</li><li>Jiang, Y., Brinker, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrothermal+synthesis+of+monodisperse+single-crystalline+alpha-quartz+nanospheres.">Hydrothermal synthesis of monodisperse single-crystalline alpha-quartz nanospheres.</a> Chem. Comm. 47 (26), 7524-7526 (2011).</li><li>Okabayashi, M., Miyazaki, K., Kono, T., Tanaka, M., Toda, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+Spherical+Particles+with+Quartz+Single.">Preparation of Spherical Particles with Quartz Single.</a> Chem. Lett. 34 (1), 58-59 (2005).</li><li>Carretero-Genevrier, A., 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=Soft-Chemistry-Based+Routes+to+Epitaxial+&#945;-Quartz+Thin+Films+with+Tunable+Textures.">Soft-Chemistry-Based Routes to Epitaxial &#945;-Quartz Thin Films with Tunable Textures.</a> Science. 340 (6134), 827-831 (2013).</li><li>Brinker, C. J., Clem, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quartz+on+Silicon.">Quartz on Silicon.</a> Science. 340 (6134), 818-819 (2013).</li><li>Brinker, C. J., Lu, Y., Sellinger, A., Fan, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaporation-Induced+Self-Assembly:+Nanostructures+Made+Easy.">Evaporation-Induced Self-Assembly: Nanostructures Made Easy.</a> Adv. Mater. 11 (7), 579-585 (1999).</li><li>Griffith, C. S., Sizgek, G. D., Sizgek, E., Scales, N., Yee, P. J., Luca, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesoporous+Zirconium+Titanium+Oxides.+Part+1:+Porosity+Modulation+and+Adsorption+Properties+of+Xerogels.">Mesoporous Zirconium Titanium Oxides. Part 1: Porosity Modulation and Adsorption Properties of Xerogels.</a> Langmuir. 24 (21), 12312-12322 (2008).</li><li>Lu, Y., 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=Continuous+formation+of+supported+cubic+and+hexagonal+mesoporous+films+by+sol-gel+dip-coating.">Continuous formation of supported cubic and hexagonal mesoporous films by sol-gel dip-coating.</a> Nature. 389 (6649), 364-368 (1997).</li><li>Drisko, G. L., 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=Water-Induced+Phase+Separation+Forming+Macrostructured+Epitaxial+Quartz+Films+on+Silicon.">Water-Induced Phase Separation Forming Macrostructured Epitaxial Quartz Films on Silicon.</a> Adv. Funct. Mater. 24 (35), 5494-5502 (2014).</li></ol>

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O método apresentado é uma abordagem de baixo para cima para produzir filmes de quartzo macroporosas sobre Si. Comparado com o método padrão de produção de filmes de quartzo, uma tecnologia de ponta para baixo com base no corte e polimento de grandes cristais hidrotermicamente cultivadas, o método descrito no protocolo permite a obtenção de películas muito finas, com espessuras entre 150 e 450 nm, que podem ser controlados com o taxa de retirada. Todos os dados experimentais sobre o controlo do quartzo filmes ...

Quando um material piezoeléctrico como quartzo-α é submetido a uma tensão de polarização que é submetido a uma deformação mecânica. Se este material é poroso, estas variações de volume podem conduzir a expansão dos poros ou contracção, a criação de um sistema sensível semelhante ao que pode ser observada em vivo organelas biológicas. 1 deformável poroso α-quartzo foi produzido utilizando microfabrico, 2, mas tais técnicas não podem ainda produzir estruturas de poros de 3-D, e são diâmetros de poros da ordem de centenas de nanómetros. A cristalização de sílica amorfa estruturada tem sido dificultada pela nucleação não homogêneo causado por altas energias de superfície e deformação arquitetônica devido ao engrossamento e de fusão. Além disso, uma vez que todas as formas de sílica são construídos sobre SiO 4 redes de tetraedros extremamente estáveis, as energias livres de formação de sílica amorfa, α-quartzo e outros SiO 2 polimorfos são quase iguais em uma ampla gama de temperaturas, fazendog difícil produzir α-quartzo, como um único polimorfo da cristalização de um gel de sílica amorfa. 3 Outro aspecto que torna mais difícil a cristalização controlada de sílica amorfa estruturado é que o quartzo apresenta uma velocidade de nucleação relativamente lento, mas uma taxa de crescimento extremamente rápido, relataram entre 10-94 nm / seg. 4,5 nucleação lenta associada a um crescimento rápido tende a gerar cristais muito maiores do que a estrutura original é nanoporoso, assim, a morfologia original é perdido. Metais alcalinos, tais como Na + e Li +, têm sido utilizados para cristalizar α-quartzo, frequentemente em combinação com o tratamento hidrotérmico. 5,6 Além disso, um Ti 4+ / Ca 2+ combinação foi utilizado para cristalizar partículas esféricas de sílica em quartzo por uma via química suave utilizando alcóxidos de silício. 7. No entanto, a cristalização controlada de uma película de sílica amorfa estruturado em quartzo manteve-se um desafio. SiO2 sob pressão ambiente e a temperaturas relativamente baixas. 8,9 epitaxia, surge a partir do desfasamento favorável entre α-quartzo e o substrato&gt; silício &lt;100, produção de filmes finos orientados piezoeléctricos. A evaporação induzida por auto-montagem para a produção de filmes de sílica mesoporosa tem sido usado desde 1999. 10 Esta técnica tem sido estudado e aplicado a um grande número de agentes modeladores sob várias condições para produzir poros de tamanhos variáveis ​​e mesofases. Verificou-se que as mudanças no tamanho mesoporo subnanometric pode ter um efeito dramático sobre a difusão de soluto através de sistemas porosos 11, validando esta grande atenção à estrutura de poros. Além disso, a acessibilidade ao sistema de silica de poro interna pode ser obtido através do controlo da fase micelar do molde 12. Aqui, a via de síntese Tchapéu permite controlo sem precedentes sobre o tamanho de poro e da espessura das camadas de sílica amorfa usando uma separação de fases é demonstrada romance. 13 Estas películas são infiltradas com (ii) sais de estrôncio e cristalizou-se para ácido a-quartzo a 1000 ° C sob ar à pressão ambiente. O tamanho de poro retainable usando este processo de cristalização é determinado, e o efeito da espessura da parede e espessura da película é estudada. Finalmente piezeletrecidade e a deformabilidade do sistema de poros, são estudados.

<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.

O progresso da síntese material foi controlado através da monitorização diferentes aspectos. Depois de o processo de imersão-revestimento pode-se observar o aspecto dos filmes, o eventual aparecimento de estruturas de difracção no local reflectida de um laser verde e a Microscopia Electrónica de Varrimento (SEM) imagens no modo de electrões com retroespalhamento (Figura 1A-B). Após o processo de cristalização é importante para gravar Atómica microscopia de ...

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.

Preparação de macroporosas Epitaxial quartzo Filmes sobre Silicon Chemical Solution Deposition por

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

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9.2K visualizações.  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. 

Vídeo: 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.

Silício policristalino de película fina de células solares com plasmonic avançada Luz-caça com armadilhas

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

Engenharia

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.

Fabricação de Sílica Ultra microresonators alto fator de qualidade

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.

Templates atomicamente definidos para crescimento epitaxial do Complexo Óxido Filmes Finos

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

Química

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.

Funcionalização litografia macia e livre de óxido Patterning silício e germânio

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

Bioengenharia

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.

Fabricação de grande-área royalty-pé ultrafinos Polymer Films

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.

Um novo método para<em&gt; In Situ</em&gt; Caracterização eletromecânica de amostras de nanoescala

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.

Fabricação de filmes de cor ultra-fino com altamente absorvente Media usando ângulo oblíquo deposição

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.

Fabricação de superfícies reativas com escova, como filmes de quitosana de polímeros co bloco Azlactone-acrescida e

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.

Cálculo Teórico e Verificação Experimental para Redução de Deslocamento em Camadas Epitaxiais de Germânio com Vazios Semicilíndricos em Silício

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.

Filmes nanoestruturados nanoestruturados de α-quartzo sobre silício: do material aos novos dispositivos

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