基于MEMS超级电容器的高介电常数CaCu_3Ti_4O_(12)薄膜制备及电学特性

Preparation and Electrical Properties of High Dielectric-constant CaCu_3Ti_4O_(12) Films for MEMS Supercapacitors

相对于电化学超级电容器,静电式电容器具有更高的功率密度和可靠性,但能量密度过低。本研究提出制备基于高介电常数薄膜CaCu_3Ti_4O_(12)(CCTO)的高能量密度MEMS静电式超级电容器。首先,以硅片为基底,通过溶胶-凝胶法在不同烧结温度700、800、900℃下制备CCTO薄膜,分别采用场发射扫描电镜(FE-SEM)和X射线衍射仪(XRD)对薄膜的形貌、组分和结晶状况进行表征,发现在800℃烧结温度下CCTO薄膜结晶状况最佳。然后,利用金属-绝缘层-半导体结构测试其电流-电压(I-V)和电容-电压(C-V)特性,计算得到薄膜的最大阈值电压和能量密度分别为47 V和3.2 J/cm^3。同时,首次对高介电常数介质膜中存在的介质充电现象进行了研究,并分析了介质充电对静电式超级电容器性能的影响。

Compared to electrochemical supercapacitors, electrostatic supercapacitors have higher power density and reliability but energy density is too low. In the present study, the preparation and electrical properties of high dielectric-constant CaCu_3 Ti4 O_（12）（CCTO） films were investigated for the high energy-density MEMS electrostatic supercapacitor. Firstly, CCTO films were synthesized at different sintering temperatures（700, 800, 900 ℃） by a sol-gel method on silicon substrate. The morphology, phase identification and crystallization of CCTO films were characterized with X-ray diffraction（XRD） and field emission scanning electron microscope（FE-SEM）. Results show that the crystallinity of the CCTO films is the best at the sintering temperature of 800 ℃. Then, the current-voltage（Ⅰ-Ⅴ） and capacitance-voltage（C-V） measurements of the CCTO films were performed on a metal-insulator-semiconductor capacitor structure. The maximum threshold voltage and energy density of the films are 47 V and 3.2 J/cm3, respectively. Meanwhile, the phenomenon of dielectric charging with high dielectric-constant in CCTO films was studied for the first time and the influence of dielectric charging on the performance of electrostatic supercapacitors was analyzed.