High dielectric tunability of Ba0.6Sr0.4TiO3 thin film deposited by radio-frequency sputtering
Nanyang Technological University, SG
Keywords: BST thin films, dielectric, sputtering
Abstract:Recently, the nonlinear dielectric property of BST thin films has been investigated for the development of frequency agile RF and highper formance microwave tunable devices, which include phase shifters, tunable filters, steerable antennas, varactors, and frequency triplers. However, many problems remain in utilizing BST for such high frequency applications. In such devices, one of the major challenges encountered for realizing the integration of BST thin films into tunable devices is the simultaneous minimization of the material’s dielectric loss and maximization of dielectric tunability. In this work, Ba0.6Sr0.4TiO3 (BST) thin films were deposited on SiO2 /Si and Pt/Ti/SiO2/Si substrates using RF sputtering technique. Due to the high temperature annealing process of the thermal plasma before deposition, well-crystallized BST films were deposited at substrate temperature of 600 °C. The dielectric constant and dielectric loss of the film at 100 kHz are 300 and 0.035, respectively. The dense microstructure make the film have low leakage current. Due to the good crystallinity of the BST films deposited by RF sputtering, high dielectric tunability up to 38.3% is achieved at low applied electric field of 100 kV cm−1. The results indicate the BST thin films are a promising application for tunable devices.