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. השג לאו / heterostructures STO <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> השג heterostructure תחמוצת מורכב מ3.4 תאי יחידה של לאו גדלו בתצהיר לייזר פעם על מצעי STO הופסקו-2 טיו. פרטים של צמיחת מדגם מתוארים בRef. 22. </li></ol> 2. Photolithographic עיבוד של דוגמאות יצירת מגעים חשמליים לממשק לאו / STO, עם כריות מליטה עבור בדי חיווט לנושאת שבב. מדרגות עיבוד הפרט מתוארות בפירוט בהמשך. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> photoresist ספין <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> ספין photoresist על הדגימות ב600 סל&quot;ד במשך 5 שניות, ולאחר מכן ב4,000 סל&quot;ד במשך 30 שניות. שכבת photoresist תהיה כ 2 מיקרומטר עבה. אופים את הדגימות ב95 מעלות צלזיוס במשך דקות 1. </li></ol></li><li style=";text-align:right;direction:rtl"> לחשוף photoresist באמצעות aligner מסכה עם ננומטר אור 320 לעם מינון של 5 mW / 2 סנטימטר 100 שניות. </li><li style=";text-align:right;direction:rtl"> לפתח את photoresist במפתח photoresist עבורr 1 דקות. </li><li style=";text-align:right;direction:rtl"> כרסום יון <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> השתמש יון טחנת Ar + להסיר 15 ננומטר של חומר (לאו וSTO) באזורים שאינו מכוסים על ידי photoresist. מניחים את הדגימות בזווית 22.5 ° לכיוון ניצבת לקרן Ar יון + הנכנסת. אם שיעור תחריט Ar + אינו מכויל, לבצע ריצת כיול על מנת להבטיח את הכמות הנכונה של חומר מוסרת. לקבוע את עומק התחריט באמצעות AFM או profilmetry המקביל. </li></ol></li><li style=";text-align:right;direction:rtl"> המקרטעת DC של טי וAu <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> הפקדת ננומטר 4 Ti, אז 25 ננומטר Au על הדגימות כך שAu עושה מגע חשמלי עם שכבת STO החשוף. הלחץ המקרטעת הוא בטווח 2-6 x 10 -7 טור, ומקרטע מתרחש עם המדגם ב RT. טרום גמגום Ti ל10 דקות עם צמצם סגור ב100 W, אז תריס פתוח וגמגום ל20 שניות ב100 וו בסיום, באופן מיידי מראש גמגום Au 1 דקות ב50 W אז גמגום Au עבור 30 שניות לדגימות ב 50 וו קאליbrate את הזמן כדי לייצר את עוביים טי וAu הרצויים. </li></ol></li><li style=";text-align:right;direction:rtl"> המראה <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> השתמש לשטוף קולי אצטון / IPA להסיר photoresist מפני שטח של הדגימות. </li></ol></li><li style=";text-align:right;direction:rtl"> שכבה שנייה <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> תהליך יתוגרפיות שני, לא כולל שלב 4 (כלומר., כרסום יון לא כולל), משמש ליצירת חיבורי חוטי זהב לרפידות מליטה בודדות. שני הדפוסים חייבים להיות מיושרים היטב כדי לוודא שהם אינם מייצרים קצרים חשמליים. </li></ol></li><li style=";text-align:right;direction:rtl"> ניקוי פלזמה. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> חבית חרט IPC משמש להסרת שאריות photoresist בתעלת הדפוס. המכשיר המשמש בW 100 ו1 טור ארגון דקות 1 </li></ol></li></ol> 3. החוט בונד לדוגמא להכין לכתיבה <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> הר המדגם לאו / STO במנשא שבב (איור 2 א) עם 28 סיכות זמינות. </li><li style=";text-align:right;direction:rtl"> אג&quot;ח חוט מבנה </li></ol> הערה: השתמש בונדר תיל כדי להפוך את ג חשמלonnections בין רפידות מליטה על המדגם ונושאת השבב. צרף mil 1 (25 מיקרומטר) חוטי זהב בין מגעים החשמליים ונושאת השבב. כתוב ננו 4. כתוב ננו <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> יצירת סקיצה רשמית של nanostructure המוליך (איור 3 א). </li><li style=";text-align:right;direction:rtl"> פתח את עורך הגרפיקה וקטורית מדרגי (SVG) (איור 3 ב). <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> השתמש בתבנית או להגדיר את גודל החלון כדי להתאים את זה של תמונת AFM. </li><li style=";text-align:right;direction:rtl"> טען את תמונת AFM של המדגם לעורך SVG. </li><li style=";text-align:right;direction:rtl"> יצירת אלמנטי nanostructure מעולף על תמונת AFM. </li></ol></li><li style=";text-align:right;direction:rtl"> טען את קובץ SVG לתכנית nanolithography. </li><li style=";text-align:right;direction:rtl"> הפעל את התוכנה ליתוגרפיה ליצור nanostructure מוליך. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> עצה השתמש V = +10 V כדי ליצור ננו, וקצה V = -10 V למחוק ננו. </li><li style=";text-align:right;direction:rtl"> להזיז את קצה c-AFM במהירות שנעה בין 200 ננומטר / שניות עד 2 מיקרומטר / sec. </li></ol></li></ol> 5. מגניב התקן ולקחת מידות <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> כבה את כל האורות הלבנים ולהשתמש במסננים אדומים / מקורות אור. </li><li style=";text-align:right;direction:rtl"> חלץ את המדגם ממערכת AFM. </li><li style=";text-align:right;direction:rtl"> טען את הדגימה למקרר הדילול (). </li><li style=";text-align:right;direction:rtl"> למדוד את ההתנגדות לעומת טמפרטורה (ב &#39;) כדוגמא הוא מקורר. </li><li style=";text-align:right;direction:rtl"> למדוד מאפייני תחבורה בטמפרטורות נמוכות (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 תחמוצת 1-5 תערוכה מגוון רחב להפליא של תופעות פיזיות מתהוות אשר מעניינים גם מבחינה מדעית ועלולים להיות שימושיים עבור יישומים 4. בפרט, הממשק בין LaAlO 3 (לאו) וSrTiO 3 (STO) 6 יכול להפגין בידוד, ניצוח, מוליכי 7, 9 התנהגות כמו ferroelectric-8, ופרומגנטי. ב2006 Thiel et al הראה 10 שיש מעבר מבודדת למתכת חדה כעובי השכבה לאו הוא גדל, עם עובי קריטי של 4 תאי יחידה (4uc). זה לאחר מכן הראה כי מבני 3uc-LAO/STO תערוכת מעבר hysteretic שניתן לשלוט באופן מקומי באמצעות מיקרוסקופ כוח אטומי מוליך בדיקה (c-AFM) 11. המאפיינים של ממשקי תחמוצת כגון LaAlO 3/3 SrTiO תלויים בהעדר או הנוכחות של ביצועאלקטרונים בממשק. ניתן לשלוט באלקטרונים אלו באמצעות אלקטרודות עליונה שער 12,13, גב שערים 10, משטח adsorbates 14, שכבות ferroelectric 15,16 ויתוגרפיה c-AFM 11. תכונה ייחודית של ליתוגרפיה c-AFM היא שניתן ליצור תכונות ננו קטנות מאוד. gating העליון חשמל, בשילוב עם כליאה דו ממדים, משמש לעתים קרובות ליצירת נקודות קוונטיות במוליכים למחצה III-V 17. לחלופין, מוליכים למחצה nanowires מעין חד ממדי יכול להיות מגודרת חשמלי בקרבה. השיטות לייצור המבנים האלה הן זמן רב ובדרך כלל בלתי הפיך. לעומת זאת, טכניקת יתוגרפיה c-AFM היא הפיכה במובן זה שnanostructure ניתן ליצור עבור ניסוי אחד, ולאחר מכן &quot;נמחק&quot; (בדומה ללוח). באופן כללי, כתיבת c-AFM מבוצעת ברמות מתח חיובי מוחל על קצה AFM, בעוד, מחיקהמתבצע באמצעות מתח שלילי. הזמן הנדרש כדי ליצור מבנה מסוים תלוי במורכבותו של המכשיר, אך הוא בדרך כלל פחות מ 30 דקות; רוב הזמן הוא בילה למחוק את הבד. הרזולוציה מרחבית הטיפוסית היא כ 10 ננומטר, אך עם כוונון נכון תכונות קטנות כמו ניתן ליצור 2 ננומטרים 18. תיאור מפורט של הליך ייצור ננו כדלקמן. הפירוט הניתן כאן צריך להיות מספיק כדי לאפשר ניסויים דומים שבוצעו על ידי חוקרים מעוניינים. יש השיטה המתוארת כאן יתרונות רבים על פני גישות מסורתיות ליתוגרפיות משמשות ליצירת ננו האלקטרוני במוליכים למחצה. השיטה ליתוגרפיה c-AFM המתואר כאן היא חלק ממעמד הרבה יותר רחב של מאמצים ליתוגרפיה מבוססות סריקת בדיקה, כוללים חמצון anodic הסריקה 19, nanolithography לטבול עט 20, דפוסים פיזואלקטריים21, וכן הלאה. טכניקת c-AFM שתוארה כאן, יחד עם השימוש בממשקי תחמוצת רומן, יכולה לייצר כמה מהמבנים האלקטרוניים הגבוהה ביותר הדיוק עם מגוון חסר תקדים של תכונות פיזיות.

<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.

התוצאות שמוצגים כאן הם נציג של תחבורת ההתנהגות שיכולה להיות מוצגת על ידי המעמד הזה של ננו, ותוארו במקומות אחרים בפירוט 23-26. בדוגמא זו, חלל nanowire נבנה (איור 4) מheterostructure לאו תא 3.3 יחידה / STO. שבילים מוליכים (המוצגים בירוק) הם בדרך כלל 10 ננומטר רחב, כפי שנקבע על ידי nanowire &quot;חיתוך&quot; ניסויי 11. מהירות הקצה והמתח לכל מגזר להגדרה באופן עצמאי מהלוח הקדמי ליתוגרפיה (איור 4), כפי שהיא מהירות כתיבת קצה. &quot;אלקטרודות וירטואליות&quot; ממשק עם אנשי קשר interfacial להבטיח כי יש חיבור חשמלי מוליך מאוד לננו. לאחר nanostructure כתוב, הוא הועבר למקרר הדילול. חשיפה לאור בבית או מתחת 550 ננומטר תפיק photoconduction לא רצוי, כך שזה שדortant להעביר את המכשיר בחושך או בסיוע (איור 5 א) אור אדום &quot;חדר חושך&quot;. חיבורי חשמל צריכים להיעשות על RT, וכמו ברוב ננו המוליכים למחצה, יש לנקוט בזהירות רבה בעת שינוי חיבורי חשמל בקירור. אם ההתקנים הוא נתון לפריקה של חשמל סטטי, זה יהיה ככל הנראה להיות מבודד. למרבה הפלא, את תפקודו של המכשיר ניתן לשחזר על ידי &quot;רכיבה על אופניים&quot; את הטמפרטורה ל 300 K והרגעות שוב. במהלך cooldown, זה שגרתי כדי לפקח על התנגדות שני הטרמינל, ואפילו התנגדות ארבעה מסוף, כפונקציה של טמפרטורה. עבור מדידות אלה מתח AC (בדרך כלל ~ 1 mV) מיושם בתדירות נמוכה (&lt;10 הרץ) לאחת מהאלקטרודות, בעוד AC הנוכחי נמדד באמצעות מגבר transimpedance. נעילה ב demodulation וסינון מתבצע באמצעות מגבר נעילה בבית מפותח. מ&quot;ק acrrent מנוטר כפונקציה של טמפרטורה (איור 5). ברגע שהמכשיר הוא מקורר לטמפרטורת הבסיס של מקרר הדילול (50 ח&quot;כ), מדידות תחבורה ארבעה מסוף מבוצעות (איור 5 ג). למדידות אלה, הנוכחיים הוא שמקורו בערוץ העיקרי של המכשיר, ואילו מתח על פני המכשיר נמדד בו זמנית. במקום למדוד עם מגבר נעילה ב, הנוכחי מתח מלא (IV) עקבות נמדדות. שיטה זו מכילה מידע נוסף והולכת ההפרש יכולה להיות מחושבת באמצעות בידול מספרי. למכשיר המסוים, ההולכה ההפרש נמדדת כפונקציה של sg מתח V בצד שער. שער זה מאפשר לפוטנציאל הכימי של המכשיר כדי להיות שונה. התחבורה באמצעות המכשיר מראה את תלות שאינה מונוטונית חזקה, המצביעה על אזורים שבהם מצור קולון מתרחש עבור ערכים קטנים יותר, וstrong מוליכות לערכים גדולים יותר של sg V. פרטים על הפרשנות הפיסית לסוג כזה של מכשיר שיתוארו במקום אחר. <img alt="איור 1" src="/files/ftp_upload/51886/51886fig1highres.jpg" /> .. איור 1 מדרגות עיבוד photolithographic שלב 1: photoresist ספין. שלב 2: לחשוף photoresist באמצעות aligner מסכה. שלב 3: לפתח photoresist. שלב 4: כרסום יון. שלב 5: DC המקרטעת להפקיד טי וAu. שלב 6: המראה. שלב 7: להפקיד את השכבה השנייה. שלב 8: ניקוי פלזמה. <img alt="איור 2" src="/files/ftp_upload/51886/51886fig2highres.jpg" /> איור 2. תמונות של heterostructures לאו / STO lithographically דוגמת. תמונה () מראה תיל 5mm x 5mm מדגם ערובה למוביל שבב. (B)<html> תמונה אופטית המציגה רפידות מליטה ואחד מהציורים. תקריב של בד אחד (C). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/51886/51886fig2highres.jpg" target="_blank">אנא לחץ כאן כדי לצפות בגרסה גדולה יותר של דמות זו.</a> <img alt="איור 3" src="/files/ftp_upload/51886/51886fig3highres.jpg" /> איור 3. () עיצוב פורמלי של nanostructure לאו / STO. (ב) פריסה מדויקת של nanostructure באמצעות גרפיקה וקטורית מדורגת קוד פתוח עורך (SVG). <img alt="איור 4" src="/files/ftp_upload/51886/51886fig4highres.jpg" /> איור 4. (א) ליתוגרפיה פנל קדמי עבור הדפוסים c-AFM. (ב &#39;) תמונת מסך מסימולטור 3D מציג עמדה ומתח של קצה C-AFM.w.jove.com/files/ftp_upload/52058/52058fig4large.jpg &quot;target =&quot; _blank &quot;&gt; לחץ כאן כדי לצפות בגרסה גדולה יותר של דמות זו. <img alt="איור 5" src="/files/ftp_upload/51886/51886fig5highres.jpg" /> איור 5. () Nanostructure לאו / STO להיות מוכנס לתוך מקרר דילול. (ב) ניטור של התנגדות מדגם כפי שהוא התקרר מ300 K 50 ח&quot;כ. ניטור (C) של מוליכות ההפרש ארבעה הטרמינל של מכשיר כפונקציה של VSG מתח שער צדדי ומתח על פני המכשיר (V4t). גרף עוצמת מוצג ביחידות של סימנס (S), ומתחים מוצגים ביחידות של וולט (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.

כתיבה ואפיון טמפרטורה הנמוכה של ננו Oxide

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

Nanyang Technological University

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.

Angle-resolved ספקטרוסקופיה Photoemission בטמפרטורות נמוכות במיוחד

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.

ייצור של ננו מהונדס תחמוצות שקופות לנהל בתצהיר ליזר פעם

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.

המצאה של תחמוצות מורכבות מוקפות מרחבית

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.

תבניות מוגדרות אטומי לEpitaxial צמיחה של תחמוצת המורכבת Thin Films

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.

חומרים אנרגטיים הכנה ותגובתיות של Gasless Nanostructured

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.

ייצור ננו-מבנה אטומי למעקב

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.

שיטות ניסיוניות מתקדמות לטמפרטורה נמוכה Magnetotransport מדידה של חומרים חדשים

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.

צמיחה ו Electrostatic/כימי מאפיינים של מתכת/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.

בתפזורת, סרט דק סינתזה של תחמוצות מיוצב אנטרופיה Variant מאלכוהול

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.

כוונון תכונות תחמוצת על ידי בקרת חמצן פנוי במהלך צמיחה וחישול

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