ZrO 2 Layer Thickness and Field Dependent Leakage Current in Ba 0.8 Sr 0.2 TiO 3 /ZrO 2 Heterostructured Thin Films
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ZrO2 Layer Thickness and Field Dependent Leakage Current in Ba0.8Sr0.2TiO3/ZrO2 Heterostructured Thin Films Santosh K. Sahoo1,2, Manjulata Sahoo3,4, and Banshidhar Majhi5 1
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401, USA
2
New Jersey Institute of Technology, Newark, New Jersey 07102, USA
3
Department of Computer Science, University at Albany-SUNY, Albany, New York 12222, USA
4
Department of Computer Science and Engineering, PCE Rourkela, Orissa 769002, India
5
Department of Computer Science and Engineering, NIT Rourkela, Orissa 769008, India
Abstract Heterostructured Ba0.8Sr0.2TiO3/ZrO2/Ba0.8Sr0.2TiO3 thin films are fabricated on the platinized Si substrates by a sol-gel process. The current versus voltage measurements are taken on these films by varying the thickness of ZrO2 layer. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in leakage current which is very essential for the low dissipation energy and hence faster operation of memory devices. It is observed that the leakage current further decreases as the ZrO2 layer thickness increases. Also it is seen that different conduction mechanisms are contributing to the leakage current in the different field regions. Poole-Frenkel (PF), space charge limited current (SCLC), and Ohmic mechanisms are the dominating conduction processes in high, medium, and low field regions respectively. An energy band diagram is given to explain the Ohmic conduction in the low field region and the Poole-Frenkel conduction mechanism in the high field region for these devices. INTRODUCTION Currently, high K materials play an important role in microelectronic devices such as capacitors and memory devices. Now a days ferroelectric barium strontium titanate [BaxSr1xTiO3, (BST)] thin film is being actively investigated for applications in dynamic random access memories (DRAM), field effect transistor (FET), and complementary metal oxide semiconductor (CMOS) devices because of its properties such as high dielectric constant, low leakage current, and high dielectric breakdown strength [1,2]. Various efforts have been made to optimize the electrical 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 [1-6]. A significant reduction in leakage current is needed for BST thin films for memory device applications. A systematic study of the impact of ZrO2 layer thickness on the leakage current of BST/ZrO2/BST
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heterostructured films and also the study of electrical conduction mechanism in different field regions are required. In this work, the dependence of leakage current
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