Influence of structural properties on RF and microwave characteristics of BaSrTiO3 films on various substrates

Ferroelectric BaxSr1-xTiO3 (BSTO, xapproximate to0.6) films were grown on various substrates (SrTiO3, LaAlO3, MgO, alpha-Al2O3 , alumina, and Y3Fe5O12) 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 chi(s) characterizing film structure and temperature T-m corresponded to maximal capacitance of BSTO varactor. Highly-oriented BSTO films of similar to 500 nm thick grown on MgO and LaAlO3 had T-m=(150-230 K), tunability K=squareepsilon(0)/epsilonsquare(E-max)approximate to1,3 - 1,5square(E(max)approximate to10 V/mum) and tan delta less than or equal to 10(-3) . The films grown on sapphire, alumina and YIG substrates had less ordered structure, lower strains, T-m=(250-260 K), Kapproximate to1,6-2,2 and tan delta greater than or equal to 10(-3). The tandelta of the investigated BSTO films at fapproximate to30 GHz was higher by approximately one order of magnitude.