TUNABLE SRTIO3 VARACTORS USING PARALLEL-PLATE AND INTERDIGITAL STRUCTURES

The dielectric properties of SrTiO3 (STO)/YBCO and STO films deposited on LaAlO3 substrates were evaluated, for potential varactor applicati ons wherein the capacitance is altered via a de voltage applied across the STO film. The optimal growth temperature for the STO films in the STO/YBCO structures was 800 degrees C; higher temperatures resulted i n interfacial degradation and poor film quality, and lower temperature s resulted in films with lower dielectric constants (epsilon(r)) and t unabilities. Interdigital varactors comprised of STO films deposited d irectly on LaAlO3 displayed higher tunabilities and significantly lowe r losses.