title: High-acoustic-impedance tantalum oxide layers for insulating acoustic reflectors.
abstract: This work describes the assessment of the acoustic properties of sputtered tantalum oxide films intended for use as high-impedance films of acoustic reflectors for solidly mounted resonators operating in the gigahertz frequency range. The films are grown by sputtering a metallic tantalum target under different oxygen and argon gas mixtures, total pressures, pulsed dc powers, and substrate biases. The structural properties of the films are assessed through infrared absorption spectroscopy and X-ray diffraction measurements. Their acoustic impedance is assessed by deriving the mass density from X-ray reflectometry measurements and the acoustic velocity from picosecond acoustic spectroscopy and the analysis of the frequency response of the test resonators.
authors.affiliation: Grupo de Microsistemas y Materiales Electrónicos del Centro de Materiales y Dispositivos Avanzados para las Tecnologías de la Informacion y Comunicaciones (GMME-CEMDA TIC), Universidad Politécnica de Madrid, Madrid, Spain.
authors.forename: Jose
authors.initials: J
authors.lastname: Capilla
authors.forename: Jimena
authors.initials: J
authors.lastname: Olivares
authors.forename: Marta
authors.initials: M
authors.lastname: Clement
authors.forename: Jesús
authors.initials: J
authors.lastname: Sangrador
authors.forename: Enrique
authors.initials: E
authors.lastname: Iborra
authors.forename: Arnaud
authors.initials: A
authors.lastname: Devos