Title of Talk: Phase Transitions and Domain Structures in Ferroelectric Thin Films

Time: 15:00, 6/29/2012 (Friday)

Place: C106, Main Building, Main Campus

Speaker：Long-Qing Chen

Abstract of Talk:

Many applications of materials require the growth of thin films on a substrate. It is known that the interface between an epitaxial film and a substrate is coherent when a film thickness is small, i.e. below the critical thickness for nucleation of interfacial dislocations.  This presentation will discuss the applications of fundamental thermodynamics and phase-field simulations to predicting phase transitions, domain structures, and properties in ferroelectric thin films.  Examples to be discussed are drawn from recent collaborations with a number of experimental groups on oxide film growth and characterizations, including PbTiO3, BaTiO3, BiFeO3 and superlattices.  It is shown that ferroelectric transition temperatures in thin films can be shifted by hundreds of degrees as compared to the corresponding bulk crystals.  It is also demonstrated that strain and electric boundary conditions can drastically modify the domain structures of a thin film as well as its properties such as coercive field, spontaneous polarization, and piezoelectric responses. It will be shown that one can use phase-field simulations to not only help interpret experimental observations but also provide guidance to achieve desirable transition temperatures, specific domain states, and domain wall orientations.

Brief Bio:

    EDUCATION
    Ph.D., M.I.T., Materials Science and Engineering, February 1990 
    M.S., SUNY at Stony Brook, Materials Science and Engineering, August 1985 
    B.S., Zhejiang University, Materials Science and Engineering, June 1982 

    EXPERIENCE
    Professor, 07/2002 - present, Department of Materials Science and Engineering, The Pennsylvania State University. 
    Associate Head for Graduate Studies, 01/2000 - 06/2002, Department of Materials Science and Engineering, The Pennsylvania State University. 
    Associate Professor, 07/1998 - 06/2002, Department of Materials Science and Engineering, The Pennsylvania State University. 
    Assistant Professor of Material Science and Engineering, 05/1992 - 06/1998, Department of Materials Science and Engineering, The Pennsylvania State University.

    Postdoctoral Associate, 01/1990 - 04/1992, Department of Materials Science and Engineering, Rutgers University. 

    RESEARCH INTERESTS
    Materials theory and computer modeling

     PUBLICATIONS AND PRESENTATIONS
    350 total authored or co-authored publications with more than 300 collected in Web of Science
    More than 200 invited presentations
    Chen's publications have been cited for more than 8000 times with an H-index of 47