Large-area atomic-smooth polyvinylidene fluoride Langmuir-Blodgett film exhibiting significantly improved ferroelectric and piezoelectric responses

• 作者: Shan He Mengfan Guo Zhenkang Dan Shun Lan Weibin Ren Le Zhou Yue Wang Yuhan Liang Yunpeng Zheng Jiayu Pan Yang Shen
• 来源期刊: 科学通报（英文版）
• 年，卷（期）: 2021,（11）
• 所属期刊栏目: ARTICLES
• 页码范围: 1080-1090
• 页数: 11页
• 语种: 英文

摘要

Large roughness and structure disorder in ferroelectric ultrathin Langmuir-Blodgett (LB) film results in severe space scatter in electrical,ferroelectric and piezoelectric characteristics,thus limiting the nanos-cale research and reliability of nano-devices.However,no effective method aiming at large-area uniform organic ferroelectric LB film has ever been reported to date.Herein,we present a facile hot-pressing strat-egy to prepare relatively large-area poly(vinylidene fluoride) (PVDF) LB film with ultra-smooth surface root mean square (RMS) roughness is 0.3 nm in a 30 μm × 30 μm area comparable to that of metal sub-strate,which maximized the potential of LB technique to control thickness distribution.More impor-tantly,compared with traditionally annealed LB film,the hot-pressed LB film manifests significantly improved structure uniformity,less fluctuation in ferroelectric characteristics and higher dielectric and piezoelectric responses,owing to the uniform dipole orientation and higher crystalline quality.Besides,different surface charge relaxation behaviors are investigated and the underlying mechanisms are explained in the light of the interplay of surface charge and polarization charge in the case of nanos-cale non-uniform switching.We believe that our work not only presents a novel strategy to endow PVDF LB film with unprecedented reliability and improved performance as a competitive candidate for future ferroelectric tunnel junctions (FTJs) and nano electro mechanical systems (NEMS),but also reveals an attracting coupling effect between the surface potential distribution and nanoscale non-uniform switch-ing behavior,which is crucial for the understanding of local transport characterization modulated by band structure,bit signal stability for data-storage application and the related surface charge research,such as charge gradient microscopy (CGM) based on the collection of surface charge on the biased ferro-electric domains.