Enhanced Tunable Properties of Strontium Barium Niobate Films on Dielectric Alumina Substrate at Microwaves

Abstract

(Sr,Ba)Nb2O6 (SBN) relaxor ferroelectric thin films exhibiting nonlinear properties promising for microwave applications were grown on a polycrystalline aluminum oxide substrate for the first time. Films of good crystallinity were obtained using the sputtering technique and high-temperature annealing. For all films, a significant change in the phase composition after high-temperature treatment was observed, and annealing provided a different effect on the phase composition of films deposited at different substrate temperatures. Tunable properties of the SBN films were investigated as a function of the deposition temperature and annealing conditions using planar capacitors with microwaves. The capacitor based on the strontium barium niobate film deposited at a temperature of 950 °C and subjected to annealing demonstrates a tunability of 44% and a loss tangent of 0.009 ÷ 0.022, which is expressed in the microwave commutation quality factor of 1740. This is the first successful attempt to form planar capacitive structures based on SBN films, which reveal a commutation quality factor above 1000 for tunable microwave applications.