Bu araştırma Enerji Nanobilim, Ödül Numarası DE-SC0001013 altında Enerji, Bilim Ofisi US Department tarafından finanse Enerji Frontier Araştırma Merkezi&#39;nin Merkezi&#39;nin bir parçası olarak desteklenmiştir. Biz de TiO2 filmi püskürtme ve refraktif indeksleri ölçümü yardım için Dr Max Zhang ve HP Labs Dr. Jianhua Yang teşekkür etmek istiyorum.

Nanoimprint Kalıp 1. Boş polidimetilsiloksan hazırlayın (PDMS) Yüzey <ol><li> Silikon Gofret Tedavi Süreci <ol><li> Aseton, metanol ve izopropanol ile durulama 4 inç silikon gofret temizleyin. </li><li> Azot tabancası kullanarak kurutun üfleyin. </li><li> 15 dakika içinde ıslatılmasıyla: (% 30 hidrojen peroksit ile sülfürik asit 1 karışımı 3) pirana çözeltisi kullanılarak temizleyin. </li><li> DI su ile durulayın. Azot tabancası kullanılarak kuru üfleyin. </li><li> Cam desikatörde gofret yerleştirin. Desikatöre madde (triklorosilan) serbest bir damla (20 damla = 1 mi) eklenir. </li><li> Göstergesi -762 Torr&#39;a okuyana kadar desikatörde aşağı Pompa ve 5 saat bekleyin. </li><li> Ajan bırakmadan ile tedavi edildikten gofret dışarı atın. </li></ol></li><li> PDMS Film Hazırlanması (Nanoimprint içinde Mold olarak kullanılır) <ol><li> Silikon elastomer baz, 10 g maddesi ve sertleştirme maddesi 1 g tartılır. </li><li> Aynı cam beher ekleyin. </li><li> ŞtiR ve 5 dakika boyunca bir cam çubuk ile karıştırın. </li><li> Göstergesi, tüm hava kabarcığı dışarı pompalamak için -762 Torr&#39;a okuyana kadar bir vakum desikatörde içine karışımı koyun. </li><li> Tedavi 4 inç silikon üzerine eşit olarak yayın. </li><li> PDMS filmi kurutmak için 80 ° C sıcaklıkta 7 saat boyunca vakumlu fırında üzerine PDMS ile gofret fırında. </li></ol></li></ol> 2. (Master Kalıp itibaren Çoğaltma) Nanoimprint Kalıp Hazırlama <ol><li> 1500 rpm&#39;de 30 saniye boyunca temiz boş silikon üzerine iyileştirilebilir karşı UV oniki damla (20 damla = 1 ml) (% 15.2) Spin. </li><li> Dikkatle işlenmiş silikon gofret kapalı PDMS filmin bir parça soyun. </li><li> Iyileştirilebilir karşı UV üzerine PDMS filmi koyun ve UV sonra 5 dakika karşı o kalkmasına absorbe edelim. </li><li> İki kez aynı PDMS filmde 2,1-2,3 tekrarlayın. UV, sırasıyla 3 dakika ve 1 dakika boyunca karşı azaltın. </li><li> Bir silikon ana kalıp üzerine (üç kez UV emilimi karşı sonra) PDMS filmi yerleştirin. </li><li> Azot ortamında bulunan bir bölme içerisine koyun. </li><li> 5 dakika boyunca numune tedavi için UV lambası açın. </li><li> PDMS filmi soyulabilir. terbiyeli UV ana kalıp negatif desen tutacak PDMS üzerinde direnmek. </li><li> Kullanım RF O 2 plazma PDMS kalıp tedavi etmek. (RF güç: 30 W, basınç: 260 mTorr, süresi: 1 dakika) </li><li> 2 saat süre ile serbest bırakma maddesi bir damla (20 damla = 1 mi) ile bir vakum odasına PDMS kalıp yerleştirin. </li></ol> 3. Nanoimprint Desen Transferi <ol><li> Substrat üzerinde PMMA sekiz damla (20 damla = 1 ml) (996K,% 3.1) Spin 3500 rpm&#39;de 50 sn baskılı edilecek. </li><li> 120 ° C &#39;de 5 dakika süre ile bir sıcak plaka üzerinde pişirilir. </li><li> Numune soğumasını bekleyin. </li><li> Aynı alt tabaka üzerinde UV sekiz damla (20 damla = 1 ml) iyileştirilebilir (% 3.9) karşı Spin. </li><li> Örnek (UV hem de karşı PMMA) PDMS kalıp (aşama 2&#39;de elde edilmiştir) yerleştirin. </li><li> Azot ortamında bulunan bir bölme içerisine koyun.</li><li> 5 dakika boyunca tedavi için UV lambası açın. </li><li> Peel numune kapalı PDMS kalıp ve PDMS kalıp desen numune transfer alır. </li></ol> 4. Cr Lift-off Süreci <ol><li> Kalan UV tabakası direnme ve PMMA gravür Reaktif iyon Not: ICP makine için SOP https://www.nanocenter.umd.edu/equipment/fablab/sops/etch-07/Oxford%20Chlorine%20Etcher%20SOP.pdf bulunabilir <ol><li> RIE ICP makinesinde giriş yapın. </li><li> Boş 4 inç silikon gofret yükleyin. 10 dakika boyunca temiz tarifi çalıştırın. </li><li> Boş silikon gofret çıkarın. </li><li> Başka bir temiz silikon gofret örnek takın ve makinenin içine yerleştirin. </li><li> UV 2 dakika süreyle gravür tarifi karşı çalıştırın (tarifi Tablo 1&#39;de bulunabilir). </li><li> Örnek çıkar. Boş 4 inç silikon gofret yükleyin. Yeniden çalıştırın temiz tarifi 10 dakika süreyle (Tablo 1&#39;de bulunabilir). </li><li> Temiz bir silikon yonga üzerinde örnek monteve makinenin içine yerleştirin. </li><li> 2 dakika süreyle (Tablo 1&#39;de bulunabilir) PMMA aşındırma tarifi çalıştırın. Not: Şimdi artık kazınmış olan dirençli ve yüzey maruz kalmaktadır. </li></ol></li><li> Cr E-ışın Buharlaşma <ol><li> E-ışın evaporatöre giriş yapın. </li><li> Odasına Cr metal kaynağı ve örnek yükleyin. </li><li> Kalınlığı (20 nm) ve çökelme hızı (/ sn 0.03 nm) ayarlayın. </li><li> Gerekli vakum içinde (10 -7 Torr) kadar odacığı içinde, pompa ulaşılır. </li><li> Biriktirme işlemini başlatın. </li><li> Biriktirme tamamlandıktan sonra numune dışarı atın. </li></ol></li><li> Lift-off cr Prosedürü <ol><li> 5 dakika boyunca, ultrasonik ajitasyon ile aseton içerisinde örnek bırakın. </li><li> Aseton, metanol ve izopropanol ile durulama ile örnek temizleyin. Not: off kalkacak dirençli ve yüzey gravürü için Cr maske oluşturulur üzerine Cr uçuruldu. </li></ol></li></ol> 5. TiO2 Depkonumumuzu <ol><li> Yük örneği. </li><li> Doğru akım magnetron püskürtme makinesi için parametreleri ayarlayın <ol><li> 1.5 mTor odası basıncı 100 sccm&#39;lik Ar akışı ve 130 W&#39;lık bir püskürtme gücünü kullanın </li><li> 27 ° C&#39;lik bir sıcaklık ve 20 rpm&#39;lik bir dönüş hızı aşamalı kullanın. </li></ol></li><li> Püskürtmeli sürecini başlatmak ve istenilen kalınlıkta durdurmak. </li><li> Örnek çıkarın ve 3 saat 300 ° C&#39;de oksijen ortamında TiO2 filmi tavlama. </li></ol> 6. Yüksek Karşıtlık Izgara Dağlama <ol><li> Indüktif eşleşmiş plazma (ICP) reaktif iyon aşındırma (RIE) makinenin giriş yapın. </li><li> TiO2 dağlama <ol><li> Boş 4 inç silikon gofret yükleyin. </li><li> Başlangıç ​​ve temiz tarifi çalıştırmak 10 dakika boyunca (Tablo 1 &#39;de bulunabilir). </li><li> Boş gofret yük kaldırma ve Cr maske ile örnek yüklemek. </li><li> Dağlama saati ayarlayın. TiO2 aşındırma tarifi başlatın. aşındırma işlemi olacak otootomatik dur. </li><li> Örnek boşaltın. </li></ol></li><li> SiO 2 Dağlama <ol><li> SiO 2 aşındırma tarifi kullanmak dışında adımı yineleyin 5.2. </li></ol></li></ol> 7. Yansıma Ölçümü <ol><li> Login ve ölçüm sistemi açın. </li><li> Numune tutucu yansıma standart ayna yerleştirin ve optik yolu hizalayın. </li><li> % 100 yansıma için sistem kalibre. </li><li> Yansıma standart ayna çıkar ve HCG yerleştirin. </li><li> HCG yansıma ölçün. </li><li> Verileri kaydetmek ve ölçüm sisteminin dışında oturum açın. </li></ol>

<ol>
	<li>Horne, S., 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=A+Solid+500+Sun+Compound+Concentrator+PV+Design.">A Solid 500 Sun Compound Concentrator PV Design.</a> Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on. , 694-697 (2006).</li><li>Guter, W., 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=Current-matched+triple-junction+solar+cell+reaching+41.1%+conversion+efficiency+under+concentrated+sunlight.">Current-matched triple-junction solar cell reaching 41.1% conversion efficiency under concentrated sunlight.</a> Applied Physics Letters. 94, 223504 (2009).</li><li>Shockley, W., Queisser, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detailed+Balance+Limit+of+Efficiency+of+p-n+Junction+Solar+Cells.">Detailed Balance Limit of Efficiency of p-n Junction Solar Cells.</a> Journal of Applied Physics. 32, 510-519 (1961).</li><li>Green, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+for+low+dimensional+structures+in+photovoltaics.">Potential for low dimensional structures in photovoltaics.</a> Materials Science and Engineering: B. 74, 118-124 (2000).</li><li>Karagodsky, V., Chang-Hasnain, 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=Physics+of+near-wavelength+high+contrast+gratings.">Physics of near-wavelength high contrast gratings.</a> Opt. Express. 20, 10888-10895 (2012).</li><li>Chou, S. Y., Krauss, P. R., Renstrom, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoimprint+lithography.">Nanoimprint lithography.</a> Journal of Vacuum Science &amp; Technology B: Microelectronics and Nanometer Structures. 14, 4129-4133 (1996).</li><li>Namiki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+FDTD+algorithm+based+on+alternating-direction+implicit+method.+Microwave+Theory+and+Techniques.">A new FDTD algorithm based on alternating-direction implicit method. Microwave Theory and Techniques.</a> IEEE Transactions on. 47, 2003-2007 (1999).</li><li>Moharam, M. G., Gaylord, T. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rigorous+coupled-wave+analysis+of+planar-grating+diffraction.">Rigorous coupled-wave analysis of planar-grating diffraction.</a> J. Opt. Soc. Am. 71, 811-818 (1981).</li><li>Yao, Y., Liu, H., Wu, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectrum+splitting+using+multi-layer+dielectric+meta-surfaces+for+efficient+solar+energy+harvesting.">Spectrum splitting using multi-layer dielectric meta-surfaces for efficient solar energy harvesting.</a> Appl. Phys. A. 115, 713-719 (2014).</li><li>Yao, Y., Liu, H., Wu, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+high-contrast+gratings+for+a+parallel+spectrum+splitting+dispersive+element+in+a+concentrated+photovoltaic+system.">Fabrication of high-contrast gratings for a parallel spectrum splitting dispersive element in a concentrated photovoltaic system.</a> Journal of Vacuum Science &amp; Technology B. 32, 06FG04-06FG04-6 (2014).</li><li>Solak, H. H., 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=Sub-50+nm+period+patterns+with+EUV+interference+lithography.">Sub-50 nm period patterns with EUV interference lithography.</a> Microelectronic Engineering. 67, 56-62 (2003).</li><li>Li, Z., 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=Hybrid+nanoimprint&#8722;+soft+lithography+with+sub-15+nm+resolution.">Hybrid nanoimprint&#8722; soft lithography with sub-15 nm resolution.</a> Nano letters. 9, 2306-2310 (2009).</li><li>Yu, Z., Chen, L., Wu, W., Ge, H., Chou, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+nanoscale+gratings+with+reduced+line+edge+roughness+using+nanoimprint+lithography.">Fabrication of nanoscale gratings with reduced line edge roughness using nanoimprint lithography.</a> Journal of Vacuum Science &amp; Technology B. 21, 2089-2092 (2003).</li></ol>

The authors have nothing to disclose.

İlk olarak, TiO2 filmin kalitesi HCG performansı için çok önemlidir. TiO2 filmi daha az kayıp ve yüzey sertliğine varsa yansıma zirve daha yüksek olacaktır. Optik mod hapsi HCG bir daha düz yol ve geniş yansıma bant verebilir endekste daha yüksek bir kontrast, tarafından geliştirilmiş olacak, çünkü daha yüksek bir kırılma indeksi ile TiO2 filmi de uygundur. İkincisi, fabrikasyon hataları HCG üzerinde önemli etkileri olacaktır ve k...

Bizim modern toplum yenilenebilir enerji kaynakları, enerji tüketiminin önemli bir bölümünü hareket ettirmeden hayatta olmaz. Bunun gerçekleşmesi için, yakın gelecekte petrol bazlı enerji kaynaklarından daha düşük bir maliyetle yenilenebilir enerji hasat için bir yol bulmak zorunda. Güneş enerjisi, yeryüzünde en bol yenilenebilir enerjidir. Gelişmeler bir çok güneş enerjisi hasat yapıldığını rağmen, petrol bazlı enerji kaynakları ile rekabet edebilmek için hala çok zordur. Güneş pillerinin verimliliğini artırma güneş enerjisi hasat sistem maliyetini düşürmek için en etkili yollardan biridir. O pahalı tandem çok kavşak güneş hücreleri 2 yararlanmaya ekonomik açıdan yani optik lensler ve çanak reflektörler genellikle küçük alan güneş hücreleri üzerinde güneş enerjisi insidansı yüksek bir konsantrasyon elde etmek için en yoğun fotovoltaik (CPV) sistemlerinde 1 kullanılır CPV sistemleri ve uygun bir korumakAynı anda maliyet. Genellikle daha geniş bir güneş spektrumu yanıtı ve daha yüksek bir genel dönüşüm verimliliğine sahip bulunmakla birlikte, genellikle güneş pilleri, bir geniş alan taksit gerektiren çoğu olmayan konsantre fotovoltaik sistemler için, yüksek maliyetli tandem güneş pilleri, dahil edilemez Tek kavşak güneş pilleri 3. Son zamanlarda, paralel spektrum bölme optik yardımıyla (yani dağıtıcı eleman) ile paralel spektrum bölme fotovoltaik teknolojisi 4 yaptı mümkün benzer ya da daha iyi spektrum kapsamı ve dönüşüm verimliliği pahalı tandem güneş pilleri kullanmadan elde edilebilir. Güneş spektrumu farklı bantlar bölünebilir ve her grup emilir ve uzman tek kavşak güneş hücreleri tarafından elektriğe dönüştürülebilir. Bu şekilde, CPV sistemleri pahalıdır, tandem güneş pilleri tek kavşak güneş pili paralel bir dağılımı ile ikame edilmiş olabilirperformans ödün vermeden s. Bu raporda tasarlanan dağıtıcı eleman geliştirilmiş güneş elektrik dönüşüm verimliliği ve düşük maliyet için paralel spektrum bölme gerçekleştirmek için (bulaşık reflektörleri dayanmaktadır) bir yansıtıcı VBM sisteminde uygulanabilir. Çok Katmanlı yüksek kontrast kafesler (HCG) 5 optik bant yansıtıcı olarak çalışmak üzere HCG her katmanı tasarlayarak dağıtıcı unsur olarak kullanılır. yapıları ve dağıtıcı elemanın parametreleri sayısal optimize edilmiştir. Ayrıca, dielektrik kullanarak dağıtıcı eleman için yüksek kontrastlı ızgaraların imalat (TiO2) püskürtme, nanoimprint litografi 6 ve reaktif iyon dağlama okudu ve gösterilmiştir.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>184 SILICONE ELASTOMER KIT</td>
			<td>SYLGARD</td>
			<td></td>
			<td>Polydimethylsiloxane (PDMS)</td>
		</tr>
		<tr>
			<td>4-inch silicon wafer</td>
			<td>Universitywafer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>4-inch fused silica wafer</td>
			<td>Universitywafer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(methyl methacrylate)</td>
			<td>SIGMA-ALDRICH</td>
			<td align="right">182265</td>
			<td></td>
		</tr>
		<tr>
			<td>UV-curable resist</td>
			<td></td>
			<td></td>
			<td>Nor available on market</td>
		</tr>
		<tr>
			<td>PlasmaLab System 100</td>
			<td>Oxford Instruments</td>
			<td></td>
			<td>ICP IRE machine</td>
		</tr>
		<tr>
			<td>UV curing system for nanoimprint fabrication</td>
			<td></td>
			<td></td>
			<td>Not available on market</td>
		</tr>
		<tr>
			<td>Ocean Optics HR-4000&#160;</td>
			<td>Ocean Optics</td>
			<td>HR-4000</td>
			<td>Spectrometer with normal detector</td>
		</tr>
		<tr>
			<td>Lambda 950 UV / VIS</td>
			<td>PerkinElmer</td>
			<td></td>
			<td>spectrometer with hemisphere intergration detector</td>
		</tr>
		<tr>
			<td>JSM-7001F-LV</td>
			<td>JEOL</td>
			<td></td>
			<td>Field emission SEM</td>
		</tr>
		<tr>
			<td>DC magnetron sputtering machine</td>
			<td></td>
			<td></td>
			<td>Equipment is in HP labs, who helped us to sputter the TiO2</td>
		</tr>
		<tr>
			<td>Metal e-beam evaporator</td>
			<td>Temescal</td>
			<td>BJD-1800</td>
			<td></td>
		</tr>
	</tbody>
</table>

fabrication of high contrast gratings for the spectrum splitting dispersive element in a concentrated photovoltaic system

High contrast gratings are designed and fabricated and its application is proposed in a parallel spectrum splitting dispersive element that can improve the solar conversion efficiency of a concentrated photovoltaic system. The proposed system will also lower the solar cell cost in the concentrated photovoltaic system by replacing the expensive tandem solar cells with the cost-effective single junction solar cells. The structures and the parameters of high contrast gratings for the dispersive elements were numerically optimized. The large-area fabrication of high contrast gratings was experimentally demonstrated using nanoimprint lithography and dry etching. The quality of grating material and the performance of the fabricated device were both experimentally characterized. By analyzing the measurement results, the possible side effects from the fabrication processes are discussed and several methods that have the potential to improve the fabrication processes are proposed, which can help to increase the optical efficiency of the fabricated devices.

Şekil 1 konsantre fotovoltaik sistemi dağıtıcı elemanın (katmanlı yüksek kontrast ızgara (HCG)) uygulanmasını gösterir. Güneş ışığı birinci birincil ayna tarafından yansıtılır ve kiriş yansıtılır ve farklı dalga boylarında değişik bantlar ayrılır yansıtıcı dağıtıcı elemanın, çarparak edilir. Her bant elektrik için en iyi emilim ve dönüşüm için güneş pili dizisinde belli bir yere vurmak olacaktır. Bu sisteme önemli tasarım ve HCG çoklu katmanlardan ol...

Watch this Scientific Journal Video about Fabrication of High Contrast Gratings for the Spectrum Splitting Dispersive Element in a Concentrated Photovoltaic System at JoVE.com

Fabrication of High Contrast Gratings for the Spectrum Splitting Dispersive Element in a Concentrated Photovoltaic System

The fabrication of high contrast gratings as the parallel spectrum splitting dispersive element in a concentrated photovoltaic system is demonstrated. Fabrication processes including nanoimprint lithography, TiO2 sputtering and reactive ion etching are described. Reflectance measurement results are used to characterize the optical performance.

Bir Konsantre Fotovoltaik Sistemde Spectrum Yarma Dağılım Eleman Yüksek Kontrast Gratings imalatı

High contrast gratings are designed and fabricated and its application is proposed in a parallel spectrum splitting dispersive element that can improve ...

fabrication-high-contrast-gratings-for-spectrum-splitting-dispersive

Research

JoVE Journal

Engineering

10.7K Görüntüleme.  University of Sothern California. The fabrication of high contrast gratings as the parallel spectrum splitting dispersive element in a concentrated photovoltaic system is demonstrated. Fabrication processes including nanoimprint lithography, TiO2 sputtering and reactive ion etching are described. Reflectance measurement results are used to characterize the optical performance. 

Video: Fabrication of High Contrast Gratings for the Spectrum Splitting Dispersive Element in a Concentrated Photovoltaic System

Electron Channeling Contrast Imaging for Rapid III-V Heteroepitaxial Characterization

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging (ECCI) in a scanning electron microscope (SEM). ECCI allows for imaging of defects and crystallographic features under specific diffraction conditions, similar to that possible via plan-view transmission electron microscopy (PV-TEM). A particular advantage of the ECCI technique is that it requires little to no sample preparation, and indeed can use large area, as-produced samples, making it a considerably higher throughput characterization method than TEM. Similar to TEM, different diffraction conditions can be obtained with ECCI by tilting and rotating the sample in the SEM. This capability enables the selective imaging of specific defects, such as misfit dislocations at the GaP/Si interface, with high contrast levels, which are determined by the standard invisibility criteria. An example application of this technique is described wherein ECCI imaging is used to determine the critical thickness for dislocation nucleation for GaP-on-Si by imaging a range of samples with various GaP epilayer thicknesses. Examples of ECCI micrographs of additional defect types, including threading dislocations and a stacking fault, are provided as demonstration of its broad, TEM-like applicability. Ultimately, the combination of TEM-like capabilities &#8211; high spatial resolution and richness of microstructural data &#8211; with the convenience and speed of SEM, position ECCI as a powerful tool for the rapid characterization of crystalline materials.

The use of electron channeling contrast imaging in a scanning electron microscope to characterize defects in III-V/Si heteroexpitaxial thin films is described. This method yields similar results to plan-view transmission electron microscopy, but in significantly less time due to lack of required sample preparation.

Rapid III-V Heteroepitaxial Karakterizasyonu için Elektron Channeling Kontrast Görüntüleme

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging ...

Mühendislik

Energy Dispersive X-ray Tomography for 3D Elemental Mapping of Individual Nanoparticles

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial resolution, and is even capable of providing atomically resolved elemental maps. In this technique, a highly focused electron beam is incident upon a thin sample and the energy of emitted X-rays is measured in order to determine the atomic species of material within the beam path. This elementally sensitive spectroscopy technique can be extended to three dimensional tomographic imaging by acquiring multiple spectrum images with the sample tilted along an axis perpendicular to the electron beam direction.
Elemental distributions within single nanoparticles are often important for determining their optical, catalytic and magnetic properties. Techniques such as X-ray tomography and slice and view energy dispersive X-ray mapping in the scanning electron microscope provide elementally sensitive three dimensional imaging but are typically limited to spatial resolutions of &gt; 20 nm. Atom probe tomography provides near atomic resolution but preparing nanoparticle samples for atom probe analysis is often challenging. Thus, elementally sensitive techniques applied within the scanning transmission electron microscope are uniquely placed to study elemental distributions within nanoparticles of dimensions 10-100 nm.
Here, energy dispersive X-ray (EDX) spectroscopy within the STEM is applied to investigate the distribution of elements in single AgAu nanoparticles. The surface segregation of both Ag and Au, at different nanoparticle compositions, has been observed.

The use of energy dispersive X-ray tomography in the scanning transmission electron microscope to characterize elemental distributions within single nanoparticles in three dimensions is described.

Bireysel Nanopartiküller 3D Elemental Haritalama için Enerji Dağılımı X-ışını Tomografi

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial ...

Writing Bragg Gratings in Multicore Fibers

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

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

Çok çekirdekli Fibers Bragg Izgaralar Yazma

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

Fabrication of Fully Solution Processed Inorganic Nanocrystal Photovoltaic Devices

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal inks. For the photoactive absorber layer, colloidal CdTe and CdSe nanocrystals (3-5 nm) are synthesized using an inert hot injection technique and cleaned with precipitations to remove excess starting reagents. Similarly, gold nanocrystals (3-5 nm) are synthesized under ambient conditions and dissolved in organic solvents. In addition, precursor solutions for transparent conductive indium tin oxide (ITO) films are prepared from solutions of indium and tin salts paired with a reactive oxidizer. Layer-by-layer, these solutions are deposited onto a glass substrate following annealing (200-400 &#176;C) to build the nanocrystal solar cell (glass/ITO/CdSe/CdTe/Au). Pre-annealing ligand exchange is required for CdSe and CdTe nanocrystals where films are dipped in NH4Cl:methanol to replace long-chain native ligands with small inorganic Cl- anions. NH4Cl(s) was found to act as a catalyst for the sintering reaction (as a non-toxic alternative to the conventional CdCl2(s) treatment) leading to grain growth (136&#177;39 nm) during heating. The thickness and roughness of the prepared films are characterized with SEM and optical profilometry. FTIR is used to determine the degree of ligand exchange prior to sintering, and XRD is used to verify the crystallinity and phase of each material. UV/Vis spectra show high visible light transmission through the ITO layer and a red shift in the absorbance of the cadmium chalcogenide nanocrystals after thermal annealing. Current-voltage curves of completed devices are measured under simulated one sun illumination. Small differences in deposition techniques and reagents employed during ligand exchange have been shown to have a profound influence on the device properties. Here, we examine the effects of chemical (sintering and ligand exchange agents) and physical treatments (solution concentration, spray-pressure, annealing time and annealing temperature) on photovoltaic device performance.

This protocol describes the synthesis and solution deposition of inorganic nanocrystals layer by layer to produce thin film electronics on non-conductive surfaces. Solvent-stabilized inks can produce complete photovoltaic devices on glass substrates via spin and spray coating following post-deposition ligand exchange and sintering.

Tam Çözüm İşlenmiş İnorganik nanokristal Fotovoltaik Cihazlarının İmalatı

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal ...

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

Zaman çözülmesi Mikrodalga İletkenlik aracılığıyla İnce film Fotovoltaik Malzemeler rekombinasyon Dinamikleri

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...

Challenges in Rheological Characterization of Highly Concentrated Suspensions &#8212; A Case Study for Screen-printing Silver Pastes

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the manifold requirements during processing and application of such complex fluids. In this investigation, measuring protocols for a conclusive assessment of different process relevant rheological parameters have been evaluated. This includes the determination of yield stress, viscosity, wall slip velocity, structural recovery after large deformation and elongation at break as well as tensile force during filament stretching.
The importance of concomitant video recordings during parallel-plate rotational rheometry for a significant determination of rheological quantities is demonstrated. The deformation profile and flow field at the sample edge can be determined using appropriate markers. Thus, measurement parameter settings and plate roughness values can be identified for which yield stress and viscosity measurements are possible. Slip velocity can be measured directly and measuring conditions at which plug flow, shear banding or sample spillover occur can be identified clearly. 
Video recordings further confirm that the change in shear moduli observed during three stage oscillatory shear tests with small deformation amplitude in stage I and III but large oscillation amplitude in stage II can be directly attributed to structural break down and recovery. For the pastes investigated here, the degree of irreversible, shear-induced structural change increases with increasing deformation amplitude in stage II until a saturation is reached at deformations corresponding to the crossover of G' and G'', but the irreversible damage is independent of the duration of large amplitude shear. 
A capillary breakup elongational rheometer and a tensile tester have been used to characterize deformation and breakup behavior of highly filled pastes in uniaxial elongation. Significant differences were observed in all experiments described above for two commercial screen-printing silver pastes used for front side metallization of Si-solar cells.

A protocol for a robust and application relevant rheological characterization of highly concentrated suspensions is presented. Silver pastes used for screen-printing application in solar cell production are employed as model systems.

Son derece Konsantre Süspansiyonlarının reolojik Karakterizasyonunda Zorluklar - Ekran-baskı Gümüş Pastaları için bir Vaka Çalışması

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the ...

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

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

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

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

tarafından Nano yapılı yitriya stabilize-Zirkonyum (YSZ) iskelelerinin Yüksek Sıcaklık Fabrikasyon<em&gt; Situ</em&gt; Karbon şablonu Kserojeller

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

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a high-precision chloride profile. Firstly, paste specimens are molded, cured, and exposed to cyclic wet-dry conditions. Then, powder samples at different specimen depths are grinded when the exposure age is reached. Finally, the water-soluble chloride content is detected using a silver nitrate titration method, and chloride profiles are plotted. The key to improving the accuracy of the chloride distribution along the depth is to exclude the error in the powderization, which is the most critical step for testing the distribution of chloride. Based on the above concept, the grinding method in this protocol can be used to grind powder samples automatically layer by layer from the surface inward, and it should be noted that a very thin grinding thickness (less than 0.5 mm) with a minimum error less than 0.04 mm can be obtained. The chloride profile obtained by this method better reflects the chloride distribution in specimens, which helps researchers to capture the distribution features that are often overlooked. Furthermore, this method can be applied to studies in the field of cement-based materials, which require high chloride distribution accuracy.

A protocol for obtaining a water-soluble chloride profile by using a high precision milling method is presented.

Çimento hamuru suda çözünebilir klorür dağılımı bir yüksek-tamlık şekilde tespit

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a ...

Method for Recording Broadband High Resolution Emission Spectra of Laboratory Lightning Arcs

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional camera film methods and then digital camera technology, from which several important characteristics have been derived. However, such work has always been limited due to the inherently random and non-repeatable nature of natural lightning events in the field. Recent developments in lightning test facilities now allow the reproducible generation of lightning arcs within controlled laboratory environments, providing a test bed for the development of new sensors and diagnostic techniques to understand lightning mechanisms better. One such technique is a spectroscopic system using digital camera technology capable of identifying the chemical elements with which the lightning arc interacts, with these data then being used to derive further characteristics. In this paper, the spectroscopic system is used to obtain the emission spectrum from a 100 kA peak, 100 &#181;s duration lightning arc generated across a pair of hemispherical tungsten electrodes separated by a small air gap. To maintain a spectral resolution of less than 1 nm, several individual spectra were recorded across discrete wavelength ranges, averaged, stitched, and corrected to produce a final composite spectrum in the 450 nm (blue light) to 890 nm (near infrared light) range. Characteristic peaks within the data were then compared to an established publicly available database to identify the chemical element interactions. This method is readily applicable to a variety of other light emitting events, such as fast electrical discharges, partial discharges, and sparking in electrical equipment, apparatus, and systems.

Emission spectroscopy techniques have traditionally been used to analyze inherently random lightning arcs occurring in nature. In this paper, a method developed to obtain the emission spectroscopy from reproducible lightning arcs generated within a laboratory environment is described.

Laboratuvar Yıldırım Yaylar Genişbant Yüksek Çözünürlüklü Emisyon Spectra Kayıt Yöntemi

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional ...

Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of nanowires. DEP is used for nanowire analysis, characterization, and for solution-based fabrication of semiconducting devices. The method works by applying an alternating electric field between metallic electrodes. The nanowire formulation is then dropped onto the electrodes which are on an inclined surface to create a flow of the formulation using gravity. The nanowires then align along the gradient of the electric field and in the direction of the liquid flow. The frequency of the field can be adjusted to select nanowires with superior conductivity and lower trap density. 
In this work, flow-assisted DEP is used to create nanowire field effect transistors. Flow-assisted DEP has several advantages: it allows selection of nanowire electrical properties; control of nanowire length; placement of nanowires in specific areas; control of orientation of nanowires; and control of nanowire density in the device. 
The technique can be expanded to many other applications such as gas sensors and microwave switches. The technique is efficient, quick, reproducible, and it uses a minimal amount of dilute solution making it ideal for the testing of novel nanomaterials. Wafer scale assembly of nanowire devices can also be achieved using this technique, allowing large numbers of samples for testing and large-area electronic applications.

In this paper, flow assisted dielectrophoresis is demonstrated for the self-assembly of nanowire devices. The fabrication of a silicon nanowire field effect transistor is shown as an example.

Akış yoluyla Dielectrophoresis: Yüksek performanslı çözüm processable Nanowire cihazları imalatı için düşük maliyetli bir yöntem

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of ...