within a Diblock Copolymer Matrix on Si Wafers
Professor Agis A. Iliadis
Electrical and Computer Engineering Department
University of Maryland
| Organizer:IEEE Electron Devices Society |
| Title: Development of Self-Assembled ZnO
Nanostructures within a Diblock Copolymer Matrix on Si Wafers |
| Speaker: Professor Agis A. Iliadis Electrical and Computer Engineering Department University of Maryland |
| Abstract: The development of self-assembled nanostructured materials has attracted significant attention recently, as it presents a promising approach for the functionalization of nanostructures into devices and systems. One approach to self-assembly is through the microphase separation observed in diblock copolymers. Diblock copolymers, consisting of a "majority" and a "minority" block, are macromolecules composed of sequences of blocks of chemically distinct repeat units. The chemical link between different blocks prevents phase separation on the macroscopic length scale, but allows microphase separation of the two blocks leading to self-assembled spherical, cylindrical, bi-continuous, and lamellar morphologies of the minority polymer block. These self-assembled domains are essentially monodisperse and have nanometer dimensions, with morphology and domain sizes generally controlled by adjusting the length of each block and the total molecular mass. In the present work a dopant precursor (ZnCl2) that attaches itself to the minority block is incorporated at room temperature in liquid phase and then converted into self-assembled ZnO nanostructures within the diblock copolymer matrix, using wet and dry chemical processing techniques. The nanocomposite polymer is applied to Si wafer surfaces using current CMOS device processing techniques, such as spin-on application, photolithographic processing, metallization, and dry etching schemes to remove the polymer matrix selectively and expose the nanostructures. The work examines two copolymer systems. The one is the norbornene (majority)-norbornene- dicarboxylic acid (minority block) system, and the other is the polystyrene (majority)-polyacrylic-acid (minority) copolymer. The interest in ZnO is due to the piezoelectric and optoelectronic properties of this wide band gap (Eg=3.3 eV) metal-oxide semiconductor. Due to its high room temperature exciton binding energy (60 meV), it shows promise for UV lasing action and optical detection. When controlled nanocrystalline structures of this system are developed, reduced dimensionality and confinement to nanoscale dimensions can be studied in order to develop a better understanding of the capabilities of such material. This novel approach is shown to deliver ZnO nanostructures on Si and SiO2 surfaces with size distribution between 7 and 15 nm for the norbornene system, and between 150 and 250 nm for the styrene system. Acknowledgements: The support by a National Science Foundation Grant # ECS-9980794, is gratefully acknowledged. The help and assistance of my co-workers Dr. P. Kofinas, from the University of Maryland, and Dr. U. Lee from the Army Research Lab, and our students, H. A. Ali, R. F. Mulligan, and A. V. W. Cresce, is also gratefully acknowledged. |
| Biography: Dr. Iliadis is an Associate Professor at the Electrical Engineering Deartment of the University of Maryland at College Park, and the Director of the Semiconductor Research Laboratory (SRL). He received his M.Sc. and Ph.D. degrees in Electrical Engineering, from the University of Manchester Institute of Science and Technology (UMIST), Dept. of Electrical Engineering and Electronics, UK, in January 1977 and March 1980 respectively. His expertise is in the area of elemental and compound semiconductor materials and devices. His contributions are in III-V heterojunction devices, InP MESFETs, SOI MOSFET's, ohmic metallizations, molecular beam epitaxial (MBE) growth, pulsed laser deposition (PLD), and wide band-gap SiC and ZnO technology. He is the author and co-author of over 110 Journal, Book and Conference publications. He is a senior member of IEEE, and a Distinguished Lecturer in the IEEE-EDS Society. He is a member of MRS, LEOS, InstPhys (UK), SPIE, TMS, and ECS and s served in several Conference Committees. |
| Time and Location: Thursday, May 15 at 6:00 p.m. University of Toronto, Galbraith Building room 248 The Galbraith Building is located at 35 St. George Street. All are welcome. Pizza will be served at 5:40 p.m CONTACT: Emanuel Istrate, e.istrate@ieee.org |
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