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Poster REU 2016

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Poster REU 2016

  1. 1.  3-hydroxyphenalenone (3-HPLN) was chosen as the source material to prepare organic thin films on Al2O3 substrates  Films were deposited using thermal evaporation under high vacuum. (EvoVac)  Substrate temperature was adjusted to control the film morphology  Atomic Force Microscopy (AFM) was used to measure the surface morphology of the thin films This work was supported by the National Science Foundation (NSF) through the Centers of Research Excellence in Science and Technology (CREST, HRD-1345163), and by the Nebraska Materials Research Science and Engineering Center (MRSEC, DMR-1420645). Dr. Yuewei Yin, Kishan Kumar Sinha, Xiaozhe Zhang; Physics and Astronomy, UNL Thank you to UNL Physics and Astronomy Department, for hosting this internship.  Organic electronics are gaining relevance due to their flexibility and low cost. In particular, organic thin films play critical roles in these applications for replacing certain inorganic counter parts.  Preparing organic thin films of smooth morphology is necessary for application. Here we study the effect of growth conditions on film morphology in physical vapor deposition processes. Abstract Purpose Comparison of 3-HPLN and Croconic Acid Analysis Conclusion Acknowledgements Procedure  Clean the Al2O3 substrate which is then placed inside the chamber.  Pump down the chamber to high vacuum (110 -7 Torr)  Begin to heat the organic source to the sublimation point; cooling down the substrate if needed.  Open the shutter to allow the organic molecules to deposit onto the substrate.  AFM for morphology characterization. Instrumentation References 1 Slashgear.com http://www.slashgear.com/lg-pumps-8-7bn-into-oled-for-your-car- tv-and-wrist-27416167/ Line scan of the images at RT (left) and -80 °C (right). EvoVac Deposition: High vacuum for sublimation of organic materials. Variable substrate temperature from - 160C to 200C for controlling the film growth 3-HPLN at -15C: • Thickness: 40nm • Abled to see some holes on the surface. 3-HPLN at RT: • Thickness: 40nm • Grown close together, not smooth 3-HPLN at -80C • Thickness: 40nm • Grew in Island style wouldn’t be a good surface A Study of the Morphology of Organic Thin Films: Nicole Lopez1, Xuanuan Jiang2, Dr. Xiaoshan Xu2 1Department of Physics, California State University, San Bernardino, CA, USA 2Department of Physics and Astronomy at University of Nebraska-Lincoln, NE, USA Surface Morphologies Croconic Acid(CA) at -30C:  Covered the whole substrate surface  Has low roughness of 3.5nm. 3-HPLN at -30C: • Thickness: 40nm • Rough but has a nearly continues surface. Atomic Force Microscope(AFM): Scanning probe to determine the surface morphology Surface roughness, coverage can be found from the AFM images Vaporized material Deposition of thin film Source Material Heater Vacuum Chamber Source Holder 3-HPLN at -30C:  Covered most of the surface, can observe some holes.  Has high roughness of 50nm . Nebraska MRSEC The picture to the left shows how the flexibility of the organic thick films may impact and even revolutionize the consumer electronics1. Liquid Nitrogen Reservoir 1.0µm 890nm Substrate Temperature Coverage Shape Size Room Temp 97% Round/oval 268 nm -15 °C 68% Oval, pointed in various directions 247 nm -30 °C 88% Round, slanted 223 nm -80 °C 75% Needle shaped, random orientation 251 nm Best surface at various substrate temperature was -30 °C. At -30 °C 3-HPLN covers 88% of the surface but has a roughness of 50 nm. A comparison of Croconic acid and 3-HPLN found that Croconic acid had a smoother surface, with 97% Coverage and 3.5nm Roughness. Substrate By using the AFM, we obtained the images of the surface of the thin films to analyze how various sub. Temperatures effected the morphologies