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National Science Foundation Outcome: Epitaxial integration of VO 2 based thin film heterostructures on sapphire and silicon substrates of various orientations.

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Presentation on theme: "National Science Foundation Outcome: Epitaxial integration of VO 2 based thin film heterostructures on sapphire and silicon substrates of various orientations."— Presentation transcript:

1 National Science Foundation Outcome: Epitaxial integration of VO 2 based thin film heterostructures on sapphire and silicon substrates of various orientations. By controlling the epitaxial growth of VO 2 films, specifically the [001] direction and defect concentration, we are able to control the strain during semiconductor-to- metal phase transition, and hence the characteristics of the transition, needed for infrared sensor device applications. Impact: The current research impacts profoundly the integration of sensor materials with existing Silicon microelectronics technology. This will enable us to create smart sensors and IR camera equipment based upon bolometer imaging arrays that won’t require costly cryogenic cooling. It also has the potential to add multi-functionality to today’s microprocessor chips that are made with silicon and sapphire substrates. Ultrafast Phase Transition and Critical Issues in Structure-Property Correlations of Vanadium Oxide Jagdish Narayan, North Carolina State University, DMR 0803663 Cross section bright field TEM micrographs taken from: (a) VO 2 /TiO 2 /m-sapphire (b) VO 2 /TiO 2 /r-sapphire. Explanation: We have grown high-quality single crystal films with controlled strain by domain matching epitaxy paradigm on substrates with a large lattice misfit, where critical thickness is less than a monolayer and the films are relaxed from the beginning. These epitaxial films exhibits a sharp transition, large amplitude, and very small hysteresis, similar to bulk single- crystal of vanadium oxide. Controlled introduction of defects by furnace annealing, laser annealing, and ion implantation to manipulate SMT properties and novel magnetic properties. The SMT characteristics of VO 2 films of VO 2 /NiO/YSZ heterostructure are excellent in terms of amplitude of the resistance change. TEM cross section of VO 2 /NiO/YSZ/Si(001) heterostructure Resistance versus temperature in: (a) VO 2 /TiO 2 /m- sapphire, (b) VO 2 /TiO 2 /r-sapphire, and (c) VO 2 /TiO 2 /c- sapphire heterostructures. Sharp transitions in the heterostructures were observed.the SMT temperature changes significantly from about 313 K to about 354 K for different substrates. This shift of the transition temperature toward higher or lower temperatures has been attributed to tensile or compressive strains along the c-axis of tetragonal VO 2, respectively.

2 National Science Foundation In less than three years, this program has graduated three very successfully employed PhDs, trained seven undergraduates, and over a dozen papers in archival journals and equal number in conference proceedings, and several invited talks. Under PI’s leadership, NCSU launched M.S. degree course in Nanoengineering, where students from all over the world including minority (NCA&T and Shaw) institutions, can finish their degree, held very popular ASM Camp for high-school seniors, and transferred technology to Kopin Corporation. PI has received TMS RF Mehl Gold Medal and Prize for his pioneering contributions and leadership in materials science worldwide. 2014 TMS RF Mehl Medal Symposium on Frontiers in Nanostructured Materials and Their Applications (February 16-20, 2014: San Diego, CA) honors Professor Jay Narayan, The John Fan Family Distinguished Chair Professor, N C State University. Graduate students: Ms. Roya Molaei (middle) will finish her PhD within year, Ms. Yvonne LEE (R) and Ms. S. Punugupati (L) have passed PhD Qualifying Examination. http://www.mse.ncsu.edu/profile/narayan Broad Impact Highlight Jagdish Narayan, North Carolina State University, DMR 0803663


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