Dielectric Properties of BST/(Y 2 O 3 ) x (ZrO 2 ) 1-x /BST Trilayer Films

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Dielectric Properties of BST/ (Y2O3)x(ZrO2)1-x/ BST Trilayer Films Santosh K. Sahoo1,2 and D. Misra1 1

Department of Electrical and Computer Engineering, NJIT, Newark, New Jersey 07102, USA

2

National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401, USA

ABSTRACT Thin films of Ba1-xSrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and high dielectric breakdown strength. Various approaches have been used to improve the dielectric properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in dielectric constant as well as dielectric loss. In this work the effect of Y2O3 doped ZrO2 on the dielectric properties of BST/ ZrO2/ BST trilayer structure is studied. The structure Ba0.8Sr0.2TiO3/ (Y2O3)x(ZrO2)1-x/ Ba0.8Sr0.2TiO3 is deposited by a sol-gel process on platinized Si substrate. The composition (x) of the middle layer is varied while keeping the total thickness of the trilayer film constant. The dielectric constant of the multilayer film decreases with the increase of Y2O3 amount in the film whereas there is a slight variation in dielectric loss. In Y2O3 doped multilayer thin films, the dielectric loss is lower in comparison to other films and also there is good frequency stability in the loss in the measured frequency range and hence very suitable for microwave device applications. INTRODUCTION Recently, many studies have been performed on the integration of high dielectric constant materials such as Pb(Zrx,Ti1-x)O3 (PZT), PbTiO3 (PT), BaTiO3 (BT) and (BaxSr1-x)TiO3 (BST) with integrated circuit (IC) technology to fabricate reliable memory devices and tunable microwave devices. Among these materials, Ba0.8Sr0.2TiO3 ferroelectric thin film has the highest potential for application in several frequency agile microwave devices such as phase shifters, filters and varactors because of its high dielectric constant, low dielectric loss, and improved dielectric tunability [1]. Various efforts have been made to optimize the dielectric properties of BST thin films for different devices applications. Among the different approaches to optimize the properties in BST thin films, recently, a multilayer structure with a combination of BST and other dielectrics has been proven to be useful approach to improve the properties of BST film. Various multilayer structures with BST as the main constituent have been studied, for improving the properties, such as BST/ ZrO2/ BST, BST/ MgO/ BST, BST/ SiO2/ BST and BST/ BSCT/ BST [1-5]. A significant reduction in loss at high frequencies is needed for BST thin films for microwave device applications. Basu et al. [5] studied the frequency dependence of dielectric loss in BST/ BSCT/ BST multilayer films. V Reymond et al. [4] have also observed the dielectric loss dependent with frequency in the BST/ SiO2