衬底材料对Ba0.6Sr0.4TiO3薄膜介电性能的影响

Effect of Substrate Material on Dielectric Properties of Ba_(0.6)Sr_(0.4)TiO_3 Thin Film Interdigital Capacitors

采用脉冲激光沉积系统分别在LaAlO_3(001)和MgO(001)衬底上沉积了Ba_(0.6)Sr_(0.4)TiO_3(BST)薄膜,以Pt做电极分别构架了Pt/BST/MgO和Pt/BST/LaAlO_3叉指电容器。利用X射线衍射仪、原子力显微镜和Aglient E4980LCR表分别对两种薄膜的结构、表面形貌和介电特性进行表征。研究发现:两种衬底都可以实现BST(001)薄膜的外延生长,MgO和LaAlO_3衬底上BST薄膜的晶粒尺寸分别为52 nm和42 nm。在室温40 V偏置电压下,Pt/BST/MgO和Pt/BST/LaAlO_3的调谐率分别为39.68%和29.55%,最低损耗分别为0.029和0.053。这说明衬底材料的晶格常数不同,最终导致了BST薄膜介电性能的不同。

Ba0.6Sr0.4TiO3（ BST） thin films were deposited on（ 001）-oriented LaAlO3 and MgO substrates using pulsed-laser deposition. Pt films were deposited on top of the BST thin films using radio frequency magnetron sputtering to fabricate the interdigital capacitors. The structure,surface morphology and dielectric properties of the samples were characterized by X-ray diffraction（ XRD）, atomic force microscope（ AFM） and Agilent 4980 A LCR Meter,respectively. The results show that： The epitaxial BST（ 001） films deposited on two different substrates,respectively. The grain size of BST thin films deposited on MgO substrate is 52 nm,while the grain size of BST thin films deposited on LaAlO3 substrate is 42 nm. The dielectric properties of the interdigital capacitors were measured as a function of applied dc voltage（ V = 40 V） at room temperature. The tunability of the BST film interdigital capacitor deposited on MgO and LaAlO3 substrate are 39. 68% and 29. 55%,and the dielectric loss are 0. 029 and0. 053. This indicates that the difference in the lattice constants,eventually led to the different dielectric properties of BST film interdigital capacitors.