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. الحصول لاو / Heterostructures STO <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> الحصول على heterostructure أكسيد تتألف من 3.4 وحدة من خلايا لاو نما بنسبة ترسب الليزر النبضي على ركائز تيو 2 STO إنهاء. موصوفة تفاصيل النمو في عينة الرقم 22. </li></ol> 2. تجهيز العينات الطباعة التصويرية إنشاء الاتصالات الكهربائية إلى الواجهة لاوس / STO، مع منصات الترابط لوحات زيتية الأسلاك إلى الناقل رقاقة. ووصف خطوات المعالجة الفردية في التفاصيل أدناه. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> تدور مقاومة للضوء <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> تدور مقاوم الضوء على عينات في 600 دورة في الدقيقة لمدة 5 ثانية، ثم في 4،000 دورة في الدقيقة لمدة 30 ثانية. وسوف تكون طبقة مقاومة للضوء حوالي 2 ميكرون سميكة. خبز العينات في 95 درجة مئوية لمدة 1 دقيقة. </li></ol></li><li style=";text-align:right;direction:rtl"> فضح مقاومة للضوء باستخدام قناع اليجنر مع 320 نانومتر للضوء 100 ثانية مع جرعة من 5 ميغاواط / سم 2. </li><li style=";text-align:right;direction:rtl"> تطوير مقاومة للضوء في مطور مقاومة للضوء FOص 1 دقيقة. </li><li style=";text-align:right;direction:rtl"> ايون طحن <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> استخدام مطحنة أيون وصول + لإزالة 15 نانومتر من المواد (لاو وSTO) في المناطق التي لا تغطيها مقاومة للضوء. وضع العينات في 22.5 درجة زاوية لاتجاه عمودي على وصول + شعاع ايون واردة. إذا لم يتم معايرة معدل الحفر وصول +، إجراء المعايرة المدى لضمان أن تتم إزالة الكمية الصحيحة من المواد. تحديد عمق الحفر باستخدام فؤاد profilmetry أو ما يعادلها. </li></ol></li><li style=";text-align:right;direction:rtl"> DC الاخرق من الاتحاد الافريقي ومنظمة الشفافية الدولية <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> إيداع 4 نانومتر تي، ثم 25 نانومتر الاتحاد الافريقي على عينات بحيث الاتحاد الافريقي يجعل الاتصال الكهربائية مع طبقة STO عرضة للخطر. الضغط الاخرق هي في حدود 2-6 × 10 -7 عربة، والاخرق يحدث مع العينة في RT. قبل بصق تي لمدة 10 دقيقة مع مصراع يغلق عند 100 W، ثم فتح مصراع وبصق لمدة 20 ثانية في 100 دبليو وعند الانتهاء، وعلى الفور قبل بصق الاتحاد الافريقي لمدة 1 دقيقة في 50 W ثم بصق الاتحاد الافريقي لمدة 30 ثانية إلى عينات في 50 جورج كاليbrate الوقت المطلوب لإنتاج تي والاتحاد الافريقي سمك. </li></ol></li><li style=";text-align:right;direction:rtl"> انطلاقه <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> استخدام الأسيتون / IPA غسل بالموجات فوق الصوتية لإزالة مقاوم الضوء من سطح العينات. </li></ol></li><li style=";text-align:right;direction:rtl"> الطبقة الثانية <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> عملية الطباعة الحجرية الثانية، باستثناء الخطوة 4 (أي.، باستثناء أيون الطحن)، ويستخدم لإنشاء اتصالات سلك الذهب إلى منصات الترابط الفردية. يجب أن تكون أنماط اثنين الانحياز جيدا للتأكد من أنها لا تنتج شورت الكهربائية. </li></ol></li><li style=";text-align:right;direction:rtl"> تنظيف البلازما. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> يتم استخدام IPC برميل مطبوع لإزالة بقايا مقاومة للضوء في خندق النمط. الأداة المستخدمة في 100 W و 1 عربة الأرجون لمدة 1 دقيقة </li></ol></li></ol> 3. أسلاك بوند عينة لتحضير للكتابة <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> جبل العينة لاو / STO في الناقل رقاقة (الشكل 2A) مع 28 دبابيس المتاحة. </li><li style=";text-align:right;direction:rtl"> هيكل السندات الأسلاك </li></ol> ملاحظة: استخدام بوندر الأسلاك الكهربائية لجعل جonnections بين منصات الترابط على العينة والناقل رقاقة. نعلق 1 مل (25 ميكرون) أسلاك الذهب بين الاتصالات الكهربائية والناقل رقاقة. إرسال النانو 4. كتابة النانو <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> إنشاء رسم رسمية من البنية النانوية موصلة (الشكل 3A). </li><li style=";text-align:right;direction:rtl"> فتح ناقلات الرسومات للتحجيم (SVG) محرر (الشكل 3B). <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> استخدام قالب أو تحديد حجم النافذة ليتطابق مع الصورة فؤاد. </li><li style=";text-align:right;direction:rtl"> تحميل صورة فؤاد من العينة إلى محرر SVG. </li><li style=";text-align:right;direction:rtl"> إنشاء عناصر البنية النانوية مضافين على الصورة فؤاد. </li></ol></li><li style=";text-align:right;direction:rtl"> تحميل ملف SVG في برنامج nanolithography إرادة. </li><li style=";text-align:right;direction:rtl"> تشغيل برنامج الطباعة الحجرية لإنشاء البنية النانوية موصلة. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> استخدام V = +10 V تلميح لإنشاء النانو، والخامس تلميح = -10 V لمحو النانو. </li><li style=";text-align:right;direction:rtl"> نقل معلومات سرية ج فؤاد بسرعة تتراوح بين 200 نانومتر / ثانية إلى 2 ميكرون / ثانية. </li></ol></li></ol> 5. كول الأجهزة وأخذ قياسات <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> إيقاف تشغيل كافة أضواء بيضاء واستخدام المرشحات أحمر / مصادر الضوء. </li><li style=";text-align:right;direction:rtl"> استخراج عينة من نظام AFM. </li><li style=";text-align:right;direction:rtl"> تحميل العينة في الثلاجة التخفيف (A). </li><li style=";text-align:right;direction:rtl"> قياس المقاومة مقابل درجة الحرارة (B) كما يتم تبريد العينة. </li><li style=";text-align:right;direction:rtl"> قياس خصائص النقل في درجات حرارة منخفضة (C). </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.

heterostructures أكسيد 1-5 المعرض تشكيلة واسعة من الظواهر الفيزيائية بشكل ملحوظ الناشئة التي هي على حد سواء مثيرة للاهتمام علميا ويمكن أن تكون مفيدة للتطبيقات 4. على وجه الخصوص، يمكن التفاعل بين LaAlO 3 (لاو) وSrTiO 3 (STO) 6 يحمل العازلة، وإجراء، فائقة التوصيل 7، متعلق بالعازل الكهربائي الشفاف مثل 8 و 9 المغناطيسية السلوك. في عام 2006، ثيل وآخرون أظهرت أن هناك 10 انتقال حاد عازل إلى المعادن مثل سمك طبقة لاو هو زيادة، مع سمك الحرجة من 4 وحدة الخلايا (4uc). وقد تبين لاحقا أن الهياكل 3uc-LAO/STO يحمل الانتقال hysteretic التي يمكن السيطرة عليها محليا مع موصل ذرية قوة المجهر (ج فؤاد) التحقيق 11. خصائص واجهات أكسيد مثل LaAlO 3/3 SrTiO تعتمد على غياب أو وجود إجراءالإلكترونات في واجهة. هذه الالكترونات يمكن السيطرة عليها باستخدام أعلى أقطاب بوابة 12،13، والعودة بوابات 10، سطح adsorbates و14، طبقات متعلق بالعازل الكهربائي الشفاف 15،16 وج فؤاد الطباعة الحجرية 11. ومن المزايا الفريدة لج فؤاد الطباعة الحجرية هي أن ميزات النانو صغيرة جدا يمكن أن تنشأ. تبوب الأعلى الكهربائية، جنبا إلى جنب مع الحبس ثنائية الأبعاد، وغالبا ما يتم استخدامه لإنشاء نقاط الكم في أشباه الموصلات III-V 17. بدلا من ذلك، أسلاك شبه الموصلة شبه أحادية البعد يمكن بوابات كهربائيا بواسطة القرب. طرق لإنتاج هذه الهياكل هي مضيعة للوقت وعموما لا رجعة فيه. على النقيض من ذلك، فإن تقنية الطباعة الحجرية ج فؤاد هو عكسها، بمعنى أن البنية النانوية يمكن أن تنشأ عن تجربة واحدة، ثم &quot;مسح&quot; (على غرار لوحة بيضاء). عموما، يتم تنفيذ ج فؤاد الكتابة مع الفولتية الإيجابية تطبيقها على الطرف فؤاد، في حين، ومحويتم تنفيذ باستخدام الفولتية السلبية. الوقت اللازم لإنشاء بنية خاصة تعتمد على تعقيد الجهاز ولكن عادة ما يكون أقل من 30 دقيقة؛ وقضى معظم ذلك الوقت محو قماش. القرار المكانية النموذجي هو حوالي 10 نانومتر، ولكن مع ضبط السليم ملامح صغيرة مثل 2 نانومتر يمكن إنشاء 18. وصف مفصل للإجراءات النانو تلفيق التالي. التفاصيل المقدمة هنا ينبغي أن يكون كافيا للسماح التجارب المماثلة التي يتعين القيام بها من قبل الباحثين المهتمين. الطريقة الموضحة هنا العديد من المزايا على النهج معدني التقليدية المستخدمة في إنشاء النانو الإلكترونية في أشباه الموصلات. طريقة الطباعة الحجرية ج فؤاد الموصوفة هنا هي جزء من فئة أوسع بكثير من الجهود الطباعة الحجرية القائمة على المسح الضوئي مسبار، بما في ذلك المسح انوديك الأكسدة 19، وتراجع من ركلة جزاء nanolithography إرادة 20، الزخرفة كهرضغطية21، وهلم جرا. تقنية ج فؤاد الموصوفة هنا، إلى جانب استخدام واجهات أكسيد الرواية، يمكن أن تنتج بعض الهياكل الإلكترونية أعلى الدقة مع مجموعة غير مسبوقة من الخصائص الفيزيائية.

<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.

النتائج المعروضة هنا هي ممثل السلوك النقل التي يمكن عرضها من قبل هذه الفئة من النانو، ولقد وصفت في مكان آخر بتفصيل 23-26. في هذا المثال، تم بناؤها تجويف أسلاك متناهية الصغر (الشكل 4) من heterostructure لاو خلية 3.3 وحدة / STO. مسارات موصل (كما هو موضح باللون الأخضر) وعادة ما تكون 10 نانومتر واسعة، على النحو الذي يحدده أسلاك متناهية الصغر &quot;قطع&quot; التجارب 11. سرعة تلميح والجهد لكل جزء هو شكلي بشكل مستقل من لوحة الطباعة الحجرية الأمامية (الشكل 4B)، كما هو غيض سرعة الكتابة. &quot;أقطاب الظاهري&quot; أن واجهة بينية الاتصالات مع ضمان وجود اتصال كهربائي موصل للغاية إلى النانو. بعد كتابة البنية النانوية، يتم نقله إلى الثلاجة التخفيف. والتعرض للضوء أو يقل عن 550 نانومتر انتاج photoconduction غير المرغوب فيها، لذلك هو عفريتortant لنقل الجهاز في الظلام أو مع المعونة من الحمراء &quot;غرفة مظلمة&quot; (5A الشكل) الخفيفة. وينبغي بذل التوصيلات الكهربائية في RT، وكما هو الحال مع معظم أشباه الموصلات النانو، ينبغي توخي الحذر الشديد عند تغيير التوصيلات الكهربائية في درجات الحرارة المبردة. إذا تم إخضاع الأجهزة لالتفريغ الكهربائي، فإنه من المرجح أن تصبح عازلة. بشكل ملحوظ، وظائف الجهاز يمكن استردادها عن طريق &quot;ركوب الدراجات&quot; درجة الحرارة إلى 300 K وتهدئة مرة أخرى. خلال تباطوء، فمن الروتينية لمراقبة المقاومة الطرفية اثنين، وحتى المقاومة أربع المحطة، بوصفها وظيفة من درجة الحرارة. لهذه القياسات يتم تطبيق الجهد المتردد (عادة بالسيارات ~ 1) في التردد المنخفض (&lt;10 هرتز) إلى واحد من الأقطاب، بينما يتم قياس ميلان الحالي باستخدام transimpedance مكبر للصوت. قفل في الإستخلاص ويتم تنفيذ التصفية باستخدام قفل في مكبر للصوت وضعت المنزل. مكعب ميلانويتم رصد rrent بوصفها وظيفة من درجة الحرارة (الشكل 5B). مرة واحدة يتم تبريد الجهاز إلى درجة الحرارة قاعدة الثلاجة التخفيف (50 كلفن)، يتم تنفيذ قياسات نقل أربعة محطة (الشكل 5C). لهذه القياسات، مصدرها الحالية من خلال القناة الرئيسية للجهاز، بينما الجهد عبر جهاز يقاس في نفس الوقت. بدلا من قياس مع مكبر للصوت للانغلاق في، كامل الجهد الحالي (الرابع) ويتم قياس أثر. يحتوي هذا الأسلوب مزيد من المعلومات ويمكن حساب الفرق التوصيل عبر التمايز العددية. لجهاز معين، يتم قياس التوصيل التفاضلية بوصفها وظيفة من سان جرمان الجانب بوابة الجهد V. هذه البوابة تتيح إمكانية الكيميائية من الجهاز إلى تغيير. النقل من خلال الجهاز يظهر الاعتماد غير رتيب قوية، مشيرا إلى المناطق التي كولومب الحصار يأخذ مكان للقيم أصغر، والمرحاض رائحةنانوغرام الموصلية الفائقة لقيم أكبر من V سان جرمان. وسيتم وصف التفاصيل حول تفسير المادية لهذه الفئة من الأجهزة في أماكن أخرى. <img alt="الشكل 1" src="/files/ftp_upload/51886/51886fig1highres.jpg" /> . الرقم 1 الطباعة التصويرية تجهيز خطوات الخطوة 1: تدور مقاومة للضوء. الخطوة 2: فضح مقاومة للضوء باستخدام قناع اليجنر. الخطوة 3: تطوير مقاومة للضوء. الخطوة 4: أيون الطحن. الخطوة 5: DC الاخرق لإيداع تي والاتحاد الافريقي. الخطوة 6: رفع حالا. خطوة 7: إيداع الطبقة الثانية. خطوة 8: تنظيف البلازما. <img alt="الرقم 2" src="/files/ftp_upload/51886/51886fig2highres.jpg" /> الشكل 2. صور منقوشة lithographically heterostructures لاو / STO. (A) صورة تظهر 5mm العاشر 5MM الأسلاك عينة المستعبدين من الناقل رقاقة. (B)<html> الصورة البصرية تظهر منصات الترابط واحدة من لوحات زيتية. (C) عن قرب من قماش واحد. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/51886/51886fig2highres.jpg" target="_blank">الرجاء انقر هنا لمشاهدة نسخة أكبر من هذا الرقم.</a> <img alt="الرقم 3" src="/files/ftp_upload/51886/51886fig3highres.jpg" /> الرقم 3 (أ) تصميم رسمية لاو / STO البنية النانوية. (B) تخطيط دقيق من البنية النانوية باستخدام المصدر المفتوح مكافحة ناقلات الرسومات للتحجيم (SVG) المحرر. <img alt="الرقم 4" src="/files/ftp_upload/51886/51886fig4highres.jpg" /> الشكل 4 (أ) الطباعة الحجرية اللوحة الأمامية للج فؤاد الزخرفة. (B) لقطة من محاكاة 3D تظهر موقف والجهد من طرف ج فؤاد.w.jove.com/files/ftp_upload/52058/52058fig4large.jpg &quot;الهدف =&quot; _blank &quot;&gt; الرجاء انقر هنا لمشاهدة نسخة أكبر من هذا الرقم. <img alt="الرقم 5" src="/files/ftp_upload/51886/51886fig5highres.jpg" /> الرقم 5. (A) لاوس / STO البنية النانوية يجري إدراجها في الثلاجة التخفيف. (B) رصد المقاومة العينة كما يتم تبريده من 300 ك إلى 50 كلفن. (C) رصد أربع سنوات محطة تصرف الفرق من جهاز بوصفها وظيفة من VSG بوابة الجانب الجهد والجهد عبر جهاز (V4t). يتم عرض الرسم البياني كثافة عرض في وحدات سيمنز (S)، والفولتية في وحدات فولت (V).

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.

الكتابة وانخفاض درجة الحرارة توصيف أكسيد النانو

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

Universidad San Sebastian

Research

JoVE Journal

Engineering

9.9K Views.  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.

زاوية التحليل الطيفي إصدار ضوئي في حل درجات الحرارة المنخفضة جدا

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

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.

تلفيق نانو هندسيا إجراء أكاسيد شفافة من ترسب الليزر النبضي

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.

تلفيق من أكاسيد مجمع المحصورة مكانيا

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.

قوالب المعرفة بالذرة لالفوقي النمو من أكسيد مجمع الأغشية الرقيقة

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

Chemistry

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.

إعداد والتفاعلية من Gasless ذات البنية النانومترية المواد الطاقوية

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.

يمكن عزوها بالذرة البنية النانوية تلفيق

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.

طرق التجريبية المتقدمة لدرجات الحرارة المنخفضة Magnetotransport قياس المواد الجديدة

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.

النمو والخصائص الكيميائية الكتروستاتي للمعدن/ﻻلو3/SrTiO3 هيتيروستروكتوريس

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.

السائبة وتوليف رقيقة أكاسيد استقرت الانتروبيا شكل تركيبي البديل

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.

ضبط خصائص أكسيد عن طريق التحكم في شغور الأكسجين أثناء النمو والتلدين

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