Name: writing and low-temperature characterization of oxide nanostructures
Uploaded: 2014-07-18T15:00:00.000+00:00
Duration: 6 min 43 s
Description: Watch this Scientific Journal Video about Writing and Low-Temperature Characterization of Oxide Nanostructures at JoVE.com

The long-standing collaboration with Chang-Beom Eom at the University of Wisconsin-Madison, who provided the LAO/STO samples, is gratefully acknowledged. Video editing assistance from Christopher Solis is greatly appreciated. This work is supported by NSF (DMR-1104191, DMR-1124131), ARO (W911NF-08-1-0317), and AFOSR (FA9550-10-1-0524, FA9550-12-1-0268, FA9550-12-1-0057).

1.. LAO / STO heteroyapılarda Alınır <ol><li> TiO2 sonlandırılmış STO yüzeylerde darbeli lazer birikimi tarafından yetiştirilen LAO 3.4 birim hücrelerden oluşan bir oksit heteroyapı edinin. Örnek büyüme detaylı No. 22 tarif edilmiştir. </li></ol> Numune 2. Fotolitografik İşleme Bir çip taşıyıcı kablo tuvaller için yapıştırma pedleri Lao / STO arayüzüne elektrik temas oluşturun. Tek tek işlem adımları aşağıda ayrıntılı olarak tarif edilmiştir. <ol><li> Spin Fotorezist <ol><li> Daha sonra 30 saniye boyunca 4000 rpm, 5 saniye boyunca 600 rpm&#39;de numuneler üzerinde fotorezist Spin. Fotorezist tabakası, yaklaşık 2 mikron kalınlığında olacaktır. 1 dakika boyunca 95 ° C&#39;de pişirin örnekleri. </li></ol></li><li> 5 mW / cm 2 lik bir dozda 100 saniye için 320 nm ışık ile bir maske kullanılarak hizalama fotorezist Açığa. </li><li> Fo Photoresist geliştirici olarak photoresist&#39;i geliştirinr 1 dak. </li><li> İyonlama <ol><li> Fotorezist tarafından kapsanmayan alanlarda 15 malzeme nm (Lao ve STO) kaldırmak için bir Ar + iyonu değirmeni kullanın. Gelen Ar + iyon kirişe dik yönde bir 22.5 ° açıyla numuneler. Ar + aşındırma oranı kalibre değilse, malzemenin doğru miktarda kaldırılır emin olmak için bir kalibrasyon çalışması yapmak. AFM veya eşdeğer profilmetry kullanarak dağlama derinliğini belirleyin. </li></ol></li><li> Ti ve Au DC püskürtme <ol><li> Deposit 4 nm Ti, daha sonra Au maruz STO tabakasıyla elektrik teması numunelerin üzerine 25 nm Au yapar, böylece. Püskürtme basıncı aralığında 2-6 x 10 -7 Torr olan ve püskürtme oda sıcaklığında numune ile gerçekleşir. Ti çekim ile 10 dakika boyunca açık çekim, daha sonra 100 W da kapalı ön-püskürtülmesi ve tamamlanması üzerine 100 W da 20 saniye boyunca püskürtmeyle çökeltilmesi, hemen 50 W de 1 dakika boyunca Au ön püskürtmeyle çökeltilmesi sonra da numune için 30 saniye Au sputter 50 W. Caliİstenen Ti ve Au kalınlıkları üretmek için zaman brate. </li></ol></li><li> Havalanma <ol><li> Numunelerin yüzeyinden fotorezist kaldırmak için aseton / IPA ultrasonik yıkama kullanın. </li></ol></li><li> İkinci katman <ol><li> 4. adımda (yani. Hariç iyon öğütme) hariç ikinci taşbaskı süreç, bireysel bağ yastıkları altın tel bağlantıları oluşturmak için kullanılır. İki desen onlar elektrik şort üretmek değil emin olmak için iyi hizalanmış olmalıdır. </li></ol></li><li> Plazma temizleme. <ol><li> Bir IPC Namlu Etcher desen açmada Fotorezist artıklarını kaldırmak için kullanılır. 1 dakika için 100 W ve 1 Torr argon at kullanılan alet, </li></ol></li></ol> 3.. Tel Bond örnek Yazma hazırlanın <ol><li> 28 mevcut iğneli bir yonga taşıyıcı (Şekil 2A) olarak LAO / STO örnek monte edin. </li><li> Tel bağ yapısı </li></ol> NOT: Elektrik c yapmak için bir tel birleştirme düzeni kullanınnumune üzerine yapıştırma pedleri ve yonga taşıyıcı arasında onnections. Elektrik kontakları ve çip taşıyıcı arasında 1 mil (25 mikrometre) altın teller takın. Nanoyapıları yaz 4. Nanoyapılar yazın <ol><li> Iletken nano (Şekil 3A) gayri resmi bir taslak oluşturun. </li><li> Ölçeklenebilir vektör grafikleri (SVG) editör (Şekil 3B) açın. <ol><li> Bir şablon kullanın veya AFM görüntünün o maç için pencere boyutunu tanımlamak. </li><li> SVG editörü içine numunenin AFM görüntüsünü yükleyin. </li><li> AFM resmi üzerine bindirilmiş nanoyapılarını unsurları oluşturmak. </li></ol></li><li> Nanolitografi programa SVG dosya yükleyin. </li><li> Bir iletken nano yapısını oluşturmak için litografi yazılımını çalıştırın. <ol><li> Kullanım V tip = +10 nanoyapıları oluşturmak için V ve V tip = nanoyapıları silmek için -10 V. </li><li> Arasında değişen bir hızda c-AFM ucu taşı 202 mm / sn 0 nm / sn. </li></ol></li></ol> 5.. Cihaz soğutun ve Ölçümleri atın <ol><li> Tüm beyaz ışıkları kapatın ve kırmızı filtreler / ışık kaynağı kullanın. </li><li> AFM sistemden örnek ayıklayın. </li><li> Seyreltme buzdolabı (A) içine örnek yerleştirin. </li><li> Numune soğutulur olarak sıcaklığında (B) vs direncini ölçün. </li><li> Düşük sıcaklıklarda (C) &#39;de taşıma özellikleri ölçün. </li></ol>

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The authors have nothing to disclose.

Successful creation of nanostructures depends on several critical steps. It is important that the LAO/STO samples are grown with a thickness that is known to be at the boundary between the insulating and conductive phase. (Details of sample growth fall outside the scope of this paper, but are crucial for overall success.) Second, it is important to have relative humidity within the range 25-45% for successful c-AFM writing. Values below 25% are unlikely to produce conductive nanostructures, while too high humidity will generally produce uncontrollably large features. Also, temperature control of the AFM is important if the c-AFM tip needs to achieve precise registry over long periods of time. Once the nanostructures are created, they must be placed in a vacuum environment if experiments lasting longer than a few hours are to be performed. For the experiments described here, the structure is created and within minutes transferred to a vacuum environment.
It is recommend before writing that a &#8220;writing test&#8221; be performed on all relevant electrodes. In such a test, two virtual electrodes are first created, and a single nanowire is written while simultaneously monitoring the conductance. A similar test of erasure can be performed by &#8220;cutting&#8221; the nanowire shortly afterwards. If the nanostructure is decaying rapidly, the issue is most likely due either to the interfacial contacts or the canvas itself. To distinguish between these two effects, a four-terminal measurement of the conductance should be performed, and the two-terminal conductance should be compared with the four-terminal conductance as a function of time. If the two-terminal conductance is decaying more rapidly than the four-terminal conductance, then the issue is related to the electrical contacts to the interface. If the four-terminal conductance is decaying at a comparable rate, then most likely the canvas is not suitable and should be replaced.
There are natural limitations of the current method for creating nanostructures. Specifically, the writing speed for the smallest devices is limited to a few hundred nanometers per second. Speeds far above that value lead to unpredictable results. Use of parallel writing techniques are possible27,28, but are not highly developed and have their own drawbacks. The size of nanostructures that can be created is naturally limited by the scan range of the AFM being used. A high-quality AFM with closed-loop feedback in the two scan directions is highly recommended. Tracking of point-like objects on the sample surface should be performed to monitor temporal drift of the sample.
Once creation of conductive nanostructures at oxide interfaces has been mastered, there are a wide range of experimental directions that can be explored. Using this technique, a wide variety of nanostructures and devices have already been demonstrated, including nanowires18, tunnel barriers29, rectifying junctions30, field-effect transistors18, single-electron transistors31, superconducting nanowires32, nanoscale optical detectors33, and nanoscale THz emitters and detectors34.

Oksit heteroyapılar 1-5 sergi hem bilimsel ilginç ve uygulamaları 4 için potansiyel olarak yararlı olan acil fiziksel fenomenlerin oldukça geniş bir çeşitlilik. Özellikle, LaAlO 3 (LAO) ve SrTiO 3 (STO) 6 arasındaki arayüz, 8 ferroelektrik gibi ve ferromanyetik 9 davranış 7 süperiletken, iletken, yalıtkan sergileyebilir. 2006 yılında, Thiel ve diğerleri LAO tabakasının kalınlığı gibi keskin bir yalıtkan-metal geçiş olduğunu göstermiştir 4 10 birim hücreler (4uc) önemli bir kalınlık ile artar. Bu, daha sonra 3uc-LAO/STO yapılar iletken bir atomik kuvvet mikroskopu (c-AFM) probu 11 ile yerel olarak kontrol edilebilir bir histeretik geçiş sergiledikleri gösterilmiştir. Bu tür LaAlO 3/3 SrTiO gibi oksit arabirimleri özellikleri yapma varlığı veya yokluğu bağlıdırarayüzde elektronlar. Bu elektronlar geri üst geçit elektrotları 12,13, kapıları 10 kullanılarak kontrol edilebilir, yüzey 14 adzorbatlar, ferroelektrik katmanlar 15,16 ve c-AFM litografi 11. C-AFM litografi benzersiz bir özelliği, çok küçük nano özellikleri oluşturulabilir olmasıdır. Iki boyutlu hapsi ile birlikte elektrik üst geçit, çoğu zaman III-V yarı iletkenler 17 kuantum noktaları oluşturmak için kullanılır. Alternatif olarak, yarı-tek boyutlu yarı iletken nanotellerdir elektriksel yakınlığı ile Geçitli edilebilir. Bu yapıların üretilmesi için yöntemler zaman alıcıdır ve genel olarak geri dönüşümsüzdür. Buna karşılık, c-AFM litografi tekniği nanoyapılarını bir deney için yaratıldı ve sonra (bir beyaz tahtaya benzer) &quot;silinebilir&quot; olabilir anlamda geri dönüşümlüdür. Silme sırasında Genel c-AFM yazma, AFM ucuna uygulanan pozitif gerilimleri ile yapılırnegatif voltajları kullanılarak gerçekleştirilir. , Belirli bir yapı oluşturmak için gerekli süre, cihazın karmaşıklığına bağlıdır, ancak genellikle en az 30 dk; O zaman çoğu tuval silme harcanmaktadır. Tipik uzaysal çözünürlüğü yaklaşık 10 nanometre olduğunu, ancak 2 nanometre 18 olarak oluşturulabilir ile uygun ayarlama gibi küçük özellikler. Nano ölçekli üretim prosedürün ayrıntılı bir açıklaması yer almaktadır. Burada sağlanan ayrıntılı benzer deneyler ilgi araştırmacılar tarafından gerçekleştirilen izin vermek için yeterli olmalıdır. Burada anlatılan yöntemi, yarıiletkenlerin elektronik nanoyapıları oluşturmak için kullanılan geleneksel taşbaskı yaklaşımlar üzerinde birçok avantajı vardır. Burada anlatılan c-AFM litografi yöntemi tarama anodik oksidasyon 19, dip-kalem nanolitografi 20, piezoelektrik desenleme dahil tarama-prob-tabanlı litografi çabaları, çok daha geniş bir sınıfın bir parçası21, vb. Yeni arabirimleri oksit kullanımı ile birlikte, burada açıklanan c-AFM teknik, fiziksel özelliklerin benzersiz bir çeşitliliği ile en yüksek hassasiyete sahip, elektronik yapıların bazı üretebilir.

<table><tbody><tr><td>Equipment</td><td></td><td></td><td></td></tr><tr><td>Contact Aligner</td><td>Karl-Suss</td><td>MA6</td><td></td></tr><tr><td>Spinner</td><td>Solitec</td><td>5110C</td><td></td></tr><tr><td>Ion Mill</td><td>Commonwealth Scientific</td><td>8C</td><td></td></tr><tr><td>Sputtering System</td><td>Leybold-Heraeus</td><td>Z-650</td><td></td></tr><tr><td>Barrel Etcher</td><td>Branson/IPC</td><td>3000C</td><td></td></tr><tr><td>Wire Bonder</td><td>Westbond</td><td>7700E</td><td></td></tr><tr><td>AFM</td><td>Asylum Research</td><td>MFP-3D</td><td></td></tr><tr><td>Dilution Refrigerator</td><td>Quantum Design</td><td>P850</td><td></td></tr><tr><td>Ultrasonic Wash Machine</td><td>Fisher Scientific</td><td>15-335-6</td><td></td></tr><tr><td>Current Amplifier</td><td>Femto</td><td>DLPCA-200</td><td></td></tr><tr><td>Materials</td><td></td><td></td><td></td></tr><tr><td>LaAlO&lt;sub&gt;3&lt;/sub&gt;/SrTiO&lt;sub&gt;3&lt;/sub&gt;</td><td>Prof. Chang-Beom Eom</td><td></td><td>5 mm x 1 mm with ~3.4 unit cells of LAO (See Reference 18)</td></tr><tr><td>Photoresist</td><td>AZ Electronic Materials</td><td>P4210</td><td></td></tr><tr><td>Developer</td><td>AZ Electronic Materials</td><td>400K</td><td></td></tr><tr><td>Acetone</td><td>Fisher Scientific</td><td>A929SK-4</td><td></td></tr><tr><td>Isopropyl Alcohol</td><td>Fisher Scientific</td><td>A459-1</td><td></td></tr><tr><td>Deionized Water</td><td>Fisher Scientific</td><td>23-290-065</td><td></td></tr><tr><td>Gold Wire</td><td>DuPont</td><td>5771</td><td>1 mm diameter</td></tr><tr><td>Chip Carrier</td><td>NTK Technologies</td><td>IRK28F1-5451D</td><td></td></tr></tbody></table>

writing and low-temperature characterization of oxide nanostructures

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions. Oxide interfaces exhibit a wide range of properties that can be controlled include conduction, piezoelectric behavior, ferromagnetism, superconductivity and nonlinear optical properties. Recently, methods for controlling these properties at extreme nanoscale dimensions have been discovered and developed. Here are described explicit step-by-step procedures for creating LaAlO3/SrTiO3 nanostructures using a reversible conductive atomic force microscopy technique. The processing steps for creating electrical contacts to the LaAlO3/SrTiO3 interface are first described. Conductive nanostructures are created by applying voltages to a conductive atomic force microscope tip and locally switching the LaAlO3/SrTiO3 interface to a conductive state. A versatile nanolithography toolkit has been developed expressly for the purpose of controlling the atomic force microscope (AFM) tip path and voltage. Then, these nanostructures are placed in a cryostat and transport measurements are performed. The procedures described here should be useful to others wishing to conduct research in oxide nanoelectronics.

Sonuçlar Burada gösterilen Nano Bu sınıf tarafından sergilenen edilebilir ulaştırma davranış temsilidir ve başka bir yerde ayrıntılı olarak, 23-26 &#39;de tarif edilmiştir. Bu örnekte, bir nanotel boşluğu 3.3 birim hücre LAO / STO heteroyapıların dan (Şekil 4) inşa edilmiştir. Deneylerini 11 &quot;kesme&quot; tellerin tarafından belirlenen (yeşil renkte) İletken yolları, geniş genellikle 10 nm. Ucu yazma hızı olarak her segment için uç hızı ve voltaj, litografi ön panelinde (Şekil 4B) bağımsız yapılandırılabilir. &quot;Sanal elektrotlar&quot; yüzey kişileri ile bu arayüz nanoyapılarda için son derece iletken bir elektrik bağlantısı olduğundan emin olun. Nano yazıldıktan sonra, bu seyreltme buzdolabı aktarılır. 550 nm altında veya ışığa maruz kalma istenmeyen fotoiletimi üretecek, bu yüzden important karanlıkta veya kırmızı bir &quot;karanlık oda&quot; ışık (Şekil 5A) yardımı ile cihazı aktarmak. Elektrik bağlantıları, oda sıcaklığında yapılmalı ve kriyojenik sıcaklıklarda elektrik bağlantılarını değiştirirken en çok yarı iletken nanoyapılarda olduğu gibi, büyük dikkat edilmelidir. Cihazlar elektrostatik boşalmaya maruz kalırsa, büyük olasılıkla yalıtım olacak. Dikkate değer olarak, cihazın işlevselliği &quot;döngü&quot; 300 K sıcaklıkta ve tekrar soğutma ile elde edilebilir. Soğutma sırasında, bu iki uç direncinin izlenmesi için rutin olan, ve hatta dört-terminal direnç, sıcaklığın bir fonksiyonu olarak. AC akım transimpedans amplifikatör kullanılarak ölçülür ise, bu ölçümler için, bir AC voltajı (tipik olarak ~ 1 mV), elektrotlardan biri için düşük bir frekansta (&lt;10 Hz) uygulanır. Demodülasyon in-Lock ve filtreleme içeride geliştirilen bir kilit-amplifikatör kullanılarak gerçekleştirilir. Ac current sıcaklığın bir fonksiyonu (Şekil 5B) olarak izlenir. Cihaz seyreltme buzdolabında (50 mK) taban sıcaklığına kadar soğutuldu sonra, dört terminal transport ölçümleri (Şekil 5C) gerçekleştirilir. Cihaz üzerinde voltaj aynı anda ölçülür ise, bu ölçümler için, akım, cihazın ana kanal üzerinden kaynaklı. Yerine kilit-amplifikatör, tam akım-gerilim ile ölçüm (IV) iz ölçülür. Bu yöntem, daha fazla bilgi içerir ve diferansiyel iletim sayısal farklılaşma yoluyla hesaplanabilir. Belirli bir aygıt için, diferansiyel iletim yan kapı voltajı V SG bir fonksiyonu olarak ölçülür. Bu kapı, cihazın kimyasal potansiyel değiştirilmesini sağlar. Cihaz üzerinden taşıma Coulomb blokaj daha küçük değerler için yer alır ve stro ettiği bölgeleri gösteren, güçlü bir tekdüze olmayan bağımlılığını göstermektedirV sg daha büyük değerler için süperiletkenlik ng. Cihazın bu sınıf için fiziksel yorumlanmasına detayları başka bir yerde tarif edilecektir. <img alt="Şekil 1" src="/files/ftp_upload/51886/51886fig1highres.jpg" /> .. Şekil 1. fotolitografik işlem adımları Adım 1: sıkma Fotorezist. Adım 2: maske hizalama kullanarak photoresist&#39;i maruz. Adım 3: photoresist&#39;i gelişir. Adım 4: iyon freze. Adım 5: DC Ti ve Au yatırmak için sıçratma. Adım 6: asansör-off. Adım 7: ikinci kat yatırmak. Adım 8: plazma temizleme. <img alt="Şekil 2," src="/files/ftp_upload/51886/51886fig2highres.jpg" /> Şekil 2.. Lithographically desenli Lao / STO heteroyapıların Görüntüler. Bir çip taşıyıcıya bağlanmış 5mm x 5mm örnek telini gösteren (A) Görüntü. (B)<html> Yapıştırma pedleri ve tuvaller birini gösteren optik görüntü. (C), tek bir tuval Close-up. <a href="https://www.jove.com/files/ftp_upload/51886/51886fig2highres.jpg" target="_blank">, bu rakamın daha büyük bir versiyonunu görmek için buraya tıklayınız.</a> <img alt="Şekil 3," src="/files/ftp_upload/51886/51886fig3highres.jpg" /> Şekil 3. Lao / STO nano (A) Gayri tasarım. (B) bir açık kaynak ölçeklenebilir vektör grafikleri (SVG) editörü kullanarak nano hassas düzeni. <img alt="Şekil 4," src="/files/ftp_upload/51886/51886fig4highres.jpg" /> Şekil 4. C-AFM desenlendirme için (A) Litografiler ön panel. (B) 3D simülatörü Ekran konumunu ve c-AFM ucu voltajını gösteren.w.jove.com/files/ftp_upload/52058/52058fig4large.jpg &quot;target =&quot; _blank &quot;&gt; bu rakamın daha büyük bir versiyonunu görmek için buraya tıklayınız. <img alt="Şekil 5," src="/files/ftp_upload/51886/51886fig5highres.jpg" /> Şekil 5. (A) LAO / STO nanoyapılarını seyreltme buzdolabına sokulmadan. (B) numune direnci İzleme 50 mK 300 K soğutulur. Cihazın dört-terminal diferansiyel iletkenlik (C) İzleme bir fonksiyonu olarak cihaza (V4T) karşısında yan kapı gerilimi VSG ve gerilim. Siemens (S) birimleri, ve gerilim görüntülenen yoğunluğu grafiği volt (V) birimleriyle görüntülenir.

Watch this Scientific Journal Video about Writing and Low-Temperature Characterization of Oxide Nanostructures at JoVE.com

Writing and Low-Temperature Characterization of Oxide Nanostructures

Oxide nanostructures provide new opportunities for science and technology. The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique. The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

Yazma ve Oksit Nanoyapıların Düşük Sıcaklık Karakterizasyonu

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions.  Oxide ...

writing-and-low-temperature-characterization-of-oxide-nanostructures

Research

JoVE Journal

Engineering

9.9K Görüntüleme.  University of Pittsburgh. Oxide nanostructures provide new opportunities for science and technology. The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique. The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

Video: Writing and Low-Temperature Characterization of Oxide Nanostructures

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

The physical properties of a material are defined by its electronic structure. Electrons in solids are characterized by energy (&omega;) and momentum (k) and the probability to find them in a particular state with given &omega; and k is described by the spectral function A(k, &omega;). This function can be directly measured in an experiment based on the well-known photoelectric effect, for the explanation of which Albert Einstein received the Nobel Prize back in 1921. In the photoelectric effect the light shone on a surface ejects electrons from the material. According to Einstein, energy conservation allows one to determine the energy of an electron inside the sample, provided the energy of the light photon and kinetic energy of the outgoing photoelectron are known. Momentum conservation makes it also possible to estimate k relating it to the momentum of the photoelectron by measuring the angle at which the photoelectron left the surface. The modern version of this technique is called Angle-Resolved Photoemission Spectroscopy (ARPES) and exploits both conservation laws in order to determine the electronic structure, i.e. energy and momentum of electrons inside the solid. In order to resolve the details crucial for understanding the topical problems of condensed matter physics, three quantities need to be minimized: uncertainty* in photon energy, uncertainty in kinetic energy of photoelectrons and temperature of the sample.
In our approach we combine three recent achievements in the field of synchrotron radiation, surface science and cryogenics. We use synchrotron radiation with tunable photon energy contributing an uncertainty of the order of 1 meV, an electron energy analyzer which detects the kinetic energies with a precision of the order of 1 meV and a He3 cryostat which allows us to keep the temperature of the sample below 1 K. We discuss the exemplary results obtained on single crystals of Sr2RuO4 and some other materials. The electronic structure of this material can be determined with an unprecedented clarity.

The overall goal of this method is to determine the low-energy electronic structure of solids at ultra-low temperatures using Angle-Resolved Photoemission Spectroscopy with synchrotron radiation.

Ultra-düşük sıcaklıklarda Açı çözüldü Photoemission Spektroskopi

The physical properties of a material are defined by its  electronic structure. Electrons in solids are characterized by energy (&omega;)  and momentum ...

Mühendislik

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

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

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

Fabrikasyon Pulsed Lazer Biriktirme tarafından Transparent letken Oksitler Nano-mühendislik

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

Fabrication of Spatially Confined Complex Oxides

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from the inherent strong electron correlations that reside within them. These materials can also possess electronic phase separation in which regions of vastly different resistive and magnetic behavior can coexist within a single crystal alloy material. By reducing the scale of these materials to length scales at and below the inherent size of the electronic domains, novel behaviors can be exposed. Because of this and the fact that spin-charge-lattice-orbital order parameters each involve correlation lengths, spatially reducing these materials for transport measurements is a critical step in understanding the fundamental physics that drives complex behaviors. These materials also offer great potential to become the next generation of electronic devices 1-3. Thus, the fabrication of low dimensional nano- or micro-structures is extremely important to achieve new functionality. This involves multiple controllable processes from high quality thin film growth to accurate electronic property characterization. Here, we present fabrication protocols of high quality microstructures for complex oxide manganite devices. Detailed descriptions and required equipment of thin film growth, photo-lithography, and wire-bonding are presented.

We describe the use of pulsed laser deposition (PLD), photolithography and wire-bonding techniques to create micrometer scale complex oxides devices. The PLD is utilized to grow epitaxial thin films. Photolithography and wire-bonding techniques are introduced to create practical devices for measurement purposes.

Mekansal Kapalı Karmaşık Oksitler Fabrikasyon

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from ...

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.

Karmaşık Oksit İnce Filmlerin Epitaksiyel Büyüme için atomik Tanımlı Şablonlar

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

Kimya

Preparation and Reactivity of Gasless Nanostructured Energetic Materials

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the balls. Among other applications, it is a versatile technique that allows for effective preparation of gasless reactive nanostructured materials with high energy density per volume (Ni+Al, Ta+C, Ti+C). The structural transformations of reactive media, which take place during HEBM, define the reaction mechanism in the produced energetic&#160;composites. Varying the processing conditions permits fine tuning of the milling-induced microstructures of the fabricated composite particles. In turn, the reactivity, i.e., self-ignition temperature, ignition delay time, as well as reaction kinetics, of high energy density materials depends on its microstructure. Analysis of the milling-induced microstructures suggests that the formation of fresh oxygen-free intimate high surface area contacts between the reagents is responsible for the enhancement of their reactivity. This manifests itself in a reduction of ignition temperature and delay time, an increased rate of chemical reaction, and an overall decrease of the effective activation energy of the reaction. The protocol provides a detailed description for the preparation of reactive nanocomposites with tailored microstructure using short-term HEBM method. It also describes a high-speed thermal imaging technique to determine the ignition/combustion characteristics of the energetic materials. The protocol can be adapted to preparation and characterization of a variety of nanostructured energetic composites.

This protocol describes the preparation of gasless nanostructured energetic materials (Ni+Al, Ta+C, Ti+C) using the short-term high-energy ball milling (HEBM) technique. It also describes a high-speed thermal imaging method to study the reactivity of mechanically fabricated nanocomposites. These protocols can be extended to other reactive nanostructured energetic materials.

Hazırlık ve Gazsız nanoyapılı reaktivitesi Enerjik Malzemeler

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the ...

Atomically Traceable Nanostructure Fabrication

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process being used in order to maintain exquisite control over both feature size and feature density. Here, we demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. Hydrogen depassivation lithography is the first step of the nanoscale fabrication process followed by selective atomic layer deposition of up to 2.8 nm of titania to make a nanoscale etch mask. Contrast with the background is shown, indicating different mechanisms for growth on the desired patterns and on the H passivated background. The patterns are then transferred into the bulk using reactive ion etching to form 20 nm tall nanostructures with linewidths down to ~6 nm. To illustrate the limitations of this process, arrays of holes and lines are fabricated. The various nanofabrication process steps are performed at disparate locations, so process integration is discussed. Related issues are discussed including using fiducial marks for finding nanostructures on a macroscopic sample and protecting the chemically reactive patterned Si(100)-H surface against degradation due to atmospheric exposure.

We report a protocol for combining the atomic metrology of the Scanning Tunneling Microscope for surface patterning with selective Atomic Layer Deposition and Reactive Ion Etching. Using a robust process involving numerous atmospheric exposures and transport, 3D nanostructures with atomic metrology are fabricated.

Atomik İzlenebilir Nanoyapı İmalatı

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Yeni Malzemelerin Düşük sıcaklık Magnetotransport Ölçüm İleri Deneysel Yöntemler

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide electronics community. One of its hallmark features is the existence of a critical LAO thickness of 4 unit-cells (uc) for interfacial conductivity to emerge. Although electrostatic mechanisms have been proposed in the past to describe the existence of this critical thickness, the importance of chemical defects has been recently accentuated. Here, we describe the growth of metal/LAO/STO heterostructures in an ultra-high vacuum (UHV) cluster system combining pulsed laser deposition (to grow the LAO), magnetron sputtering (to grow the metal) and X-ray photoelectron spectroscopy (XPS). We study step by step the formation and evolution of the q2DES and the chemical interactions that occur between the metal and the LAO/STO. Additionally, magnetotransport experiments elucidate on the transport and electronic properties of the q2DES. This systematic work not only demonstrates a way to study the electrostatic and chemical interplay between the q2DES and its environment, but also unlocks the possibility to couple multifunctional capping layers with the rich physics observed in two-dimensional electron systems, allowing the fabrication of new types of devices.

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

We fabricate metal/LaAlO3/SrTiO3 heterostructures using a combination of pulsed laser deposition and in situ magnetron sputtering. Through magnetotransport and in situ X-ray photoelectron spectroscopy experiments, we investigate the interplay between electrostatic and chemical phenomena of the quasi two-dimensional electron gas formed in this system.

Büyüme ve Elektrostatik/kimyasal özellikleri Metal/LaAlO3/SrTiO3 Heterostructures

The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide ...

Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (Cu variant) entropy-stabilized oxides. Phase pure and chemically homogeneous (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (x = 0.11, 0.27) ceramic pellets are synthesized and used in the deposition of ultra-high quality, phase pure, single crystalline thin films of the target stoichiometry. A detailed methodology for the deposition of smooth, chemically homogeneous, entropy-stabilized oxide thin films by pulsed laser deposition on (001)-oriented MgO substrates is described. The phase and crystallinity of bulk and thin film materials are confirmed using X-ray diffraction. Composition and chemical homogeneity are confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The surface topography of thin films is measured with scanning probe microscopy. The synthesis of high quality, single crystalline, entropy-stabilized oxide thin films enables the study of interface, size, strain, and disorder effects on the properties in this new class of highly disordered oxide materials.

The synthesis of high quality bulk and thin film (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O entropy-stabilized oxides is presented.

Toplu ve bileşimsel varyant entropi stabilize oksit ince Film sentezi

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and ...

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing

Electrical, optical, and magnetic properties of oxide materials can often be controlled by varying the oxygen content. Here we outline two approaches for varying the oxygen content and provide concrete examples for tuning the electrical properties of SrTiO3-based heterostructures. In the first approach, the oxygen content is controlled by varying the deposition parameters during a pulsed laser deposition. In the second approach, the oxygen content is tuned by subjecting the samples to annealing in oxygen at elevated temperatures after the film growth. The approaches can be used for a wide range of oxides and nonoxide materials where the properties are sensitive to a change in the oxidation state.
The approaches differ significantly from electrostatic gating, which is often used to change the electronic properties of confined electronic systems such as those observed in SrTiO3-based heterostructures. By controlling the oxygen vacancy concentration, we are able to control the carrier density over many orders of magnitude, even in nonconfined electronic systems. Moreover, properties can be controlled, which are not sensitive to the density of itinerant electrons.

Oxide materials show many exotic properties that can be controlled by tuning the oxygen content. Here, we demonstrate the tuning of oxygen content in oxides by varying the pulsed laser deposition parameters and by performing postannealing. As an example, electronic properties of SrTiO3-based heterostructures are tuned by growth modifications and annealing.

Büyüme ve tavlama sırasında oksijen boşluk kontrolü ile oksit özelliklerinin ayarlanması

Electrical, optical, and magnetic properties of oxide materials can often be controlled by varying the oxygen content. Here we outline two approaches for ...