Electrical and Structural Diagnostics of Barium Strontium Titanate (BST) Thin Films
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Electrical and Structural Diagnostics of Barium Strontium Titanate (BST) Thin Films Supriya Ketkar1, Manoj Kumar Ram2,3, Ashok Kumar2,3, Thomas Weller1 and Andrew Hoff1 1
Department of Electrical Engineering, University of South Florida, Tampa, Fl 33620 Department of Mechanical Engineering, University of South Florida, Tampa, Fl 33620 3 Nanotechnology Research and Education Center, University of South Florida, Tampa, Fl 33620 2
ABSTRACT The properties of radio frequency, rf magnetron sputtered Barium Strontium Titanate (Ba1BST, thin films were investigated and compared with BST thin films deposited by solgel method with the aim of determining relationships between the oxide deposition parameters, the film structure, and the electric field dependence. This work presents noncontact electrical characterization of BST films using Corona Kelvin metrology (C-KM) which has been employed earlier only in the silicon industry. The films were structurally characterized using thickness profilometer, X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques. The use of sol-gel technique to fabricate small area metal-insulator-metal (MIM) structures is found to be beneficial from the point of saving fabrication time and production costs.
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INTRODUCTION Titanate-based dielectrics exhibit as much as a four-fold change in electric permittivity with application of a small electric field [1, 2]. Capacitance dependence on field in the dielectric enables numerous frequency-agile high frequency circuit applications [3]. In general, high-k films exhibit variable conductance due to small band offsets and defect issues [4-6]. Thus, looking at the current scenario, frequency tunable RF and microwave titanate-based ferroelectric components will be in huge demand due to their frequency agile characteristic. Next-generation communication systems have stringent limitations on high performance, cost effectiveness and miniature size. These requirements clearly pose new challenges to opt for newer materials and processes which can reduce the size, cost and time required for mass production. The recent advances in ferroelectric thin film technology can guarantee improvement in device performance and integration with semiconductor technology [7]. In recent years BST based ferroelectric thin film devices have received significant attention for applications in tunable microwave devices such as delay lines, resonators, phase shifters, and varactors [8]. BST thin films have been promising candidates due to their high dielectric constant, tunability and low dielectric loss. Dielectric-tunable properties of BST films deposited by different deposition techniques have been reported which study the effects of factors, such as oxygen vacancies, strain and stress, film thickness, grain size, Ba/Sr ratio, etc. [9-11]. Researchers have also studied doping concentrations, high temperature annealing and multilayer structures to attain higher tunability and lower loss [12–14]. The present report investigates the structural and electrical prop
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