Structure And Electric Properties Of Magnetron Sputtering BZT-BCT Based Films

Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3(BZT-BCT) has become a research hotspotin recent years because of its ultrahigh piezoelectric performance in theMorphotropic Phase Boundary (MPB), then the thin films research of this systemmaterials also gradually developed. Largest piezoelectric coefficient in currentlyreported papers about BZT-BCT films was only141pm/V, and there is a larger gapwith theoretical prediction190~250pm/V. So, get high-quality and certain texturefilms in order to improve their electrical properties has become main content in theresearch field of BZT-BCT films, at present stage. And studies for BZT-BCTcomposite films were almost zero at home and abroad. Project was based on abovementioned problems, and paper used magnetron sputtering make BZT-BCT basedfilms while feeding oxygen gap, and introduced seed layers to films, and chose thebest way to make seed layers crystallization, and combined CCTO to attainCCTO/BZT-BCT films, hoping improve the quality of thin film and theirperformance.This paper successfully used the dual target (BZT target and BZT target)co-sputtering BZT-BCT films, whose thickness in the range of220~300nm. Thesputtering atmosphere was passed into the oxygen while sputtering BZT-BCTfilms, then it found that with the amount of oxygen increased the grain size ofthose films decreased, and the RMS declined, and those films became more andmore thin. The result of XRD showed the crystalline degree of BZT-BCT filmsdropped clearly. Then the paper annealed those films with two different ways: RTAannealing and CTA annealing.After annealed those BZT-BCT films became complete crystallized. And thenumber of oxygen vacancies cut down. This improved those films quality and theird33. When the oxygen content was30, the average size of the domain ofRTA-annealed-BZT-BCT films was bout256nm, and films’ d33was213.2pm/V, Prwas6.9μC/cm2, and their dielectric constant was954when the frequency was1kHz. While the average size of the domain of CTA-annealed-BZT-BCT films wasbout177nm, and those films’ piezoelectric coefficient was up to273.7pm/V, theremnant polarization was7.3μC/cm2, and ε was128at1kHz.The seed layers (LNO and STO) were introduced into BZT-BCT films inorder to improve the film electrical properties. In this paper, there were two seedlayer crystallization methods be explored: one was that the seed layer annealedbefore the BZT-BCT films been crystallization; and the other was that films wereannealed with their seed layers. The XRD indicated the first method make BZT-BCT/LNO films and BZT-BCT/STO films appear (100) and (111) texturesrespectively. But the second method made those films preferentially along the (110)direction of growth. The AFM figures made people know that those films withtheir seed layers annealed firstly had smaller grain size and RMS. However, whenannealed with their layers films got the batter electrical properties. Maybe the thinfilms’ growth direction and stress worked.When the seed layer and the film co-crystallization at800℃, piezoelectricproperties of BZT-BCT/LNO films is excellent, their d33exceeds200, the remnantpolarization was6.4μC/cm2; BZT-BCT/STO films’ d33was83.1pm/V, and theremnant polarization31.6μC/cm2.The amorphous CCTO is ferroelectric. This paper found the proof for it thatferroelectric domains existence in non-crystalline CCTO films. The domain size ofamorphous CCTO in CCTO/BZT-BCT/LNO film surface was190nm, while inCCTO/BZT-BCT/STO thin film surface was256nm. At the same time, this papergave the hysteresis loops of these two composite thin films annealed at differenttemperatures.Finally, effects of oxygen while sputtering on the structure and electricalproperties of CCTO/BZT-BCT thin films annealed at650℃were studied. It turnout that the more oxygen the better film quality, and the ferroelectric properties inthe oxygen content of20is the best.