摘要
Thermodynamics of(001)epitaxial ferroelectric films completely relaxed due to the formation of elastic domains with a three-domain architecture is presented.The polydomain structure and electromechanical response of such films are analyzed for two cases corresponding to immobile and mobile elastic domain walls.It is shown that immobile elastic domains provide additional constraint which increases the mechanical and electrical clamping,thereby significantly reducing the piezoelectric and dielectric responses.On the other hand,a polydomain ferroelectric film adapts to the variations in the applied electric field by reversible domain wall displacements in the case of mobile domain walls.The comparison of the theory with experiments shows that the elastic domain walls are mobile in the fully relaxed films of~1μm thickness.In addition,if the substrate constraint is reduced via decreasing lateral size of a polydomain ferroelectric film,its piezoresponse will increase dramatically,as is experimentally verified on small islands of polydomain ferroelectric films.The general conclusions can be readily applied to other constrained polydomain films.
基金
J.Ouyang would like to acknowledge the“Qi-Lu Young Scholar Fund”(Grant No.31370080963003)from Shandong University,supported by the 985 Fund of Shandong University,and the project sponsored by SRF for ROCS,SEM(Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry)
J.Ouyang and W.Zhang would like to thank the financial support of the National Natural Science Foundation of China(Project Grant Nos.91122024 and 51002088)
the Shandong Province Outstanding Young Scientist Research Fund(Project Grant No.BS2010CL029)
A.L.Roytburd is grateful to NSF-DMR(No.0907122)for the support.
