Influence of Structural Properties on RF and Microwave Characteristics of BaSrTiO 3 Films on Various Substrates

Abstract

Ferroelectric Ba x Sr 1-x TiO 3 (BSTO, x , 0.6) films were grown on various substrates (SrTiO 3 , LaAlO 3 , MgO, f -Al 2 O 3 , alumina, and Y 3 Fe 5 O 12 ) using RF sputtering. The results of complex BSTO diagnostics using medium energy ion scattering (MEIS) were compared with dielectric characteristics at 1 MHz and 30 GHz. The BSTO films were different on the MEIS yield h s characterizing film structure and temperature T m corresponded to maximal capacitance of BSTO varactor. Highly-oriented BSTO films of ∼ 500 nm thick grown on MgO and LaAlO 3 had T m = (150-230 K), tunability K = l (0)/ l ( E max ) , 1,3 m 1,5 ( E max , 10 V/ w m) and tan i h 10 m 3 . The films grown on sapphire, alumina and YIG substrates had less ordered structure, lower strains, T m = (250 - 260 K), K , 1,6 - 2,2 and tan i S 10 m 3 . The tan i of the investigated BSTO films at f , 30 GHz was higher by approximately one order of magnitude.