An actuator includes a substrate, a diaphragm on the substrate, a lower electrode on the diaphragm, a piezoelectric body on the lower electrode, and an upper electrode on the piezoelectric body. A ratio of lead (Pb) and zirconium (Zr) in atomic percent (atm %) present at a grain boundary in the piezoelectric body satisfies a relation of Pb/Zr>1.7.

A piezoelectric thin film contains a lower layer and a first piezoelectric layer stacked on the lower layer. The first piezoelectric layer contains a tetragonal crystal 1 of a perovskite-type oxide. A (001) plane of the tetragonal crystal 1 is oriented in a normal direction dn of a surface of the first piezoelectric layer. A spacing of (100) planes of the tetragonal crystal 1 is a1. A spacing of (100) planes of a crystal contained in the lower layer is aL. A lattice mismatch rate between the first piezoelectric layer and the lower layer is 100×(aL−a1)/a1. The lattice mismatch rate is 3.0 to 12.1%. A rocking curve of diffracted X-rays of the (001) plane of the tetragonal crystal 1 is measured in an out-of-plane direction of the surface of the first piezoelectric layer. A FWHM of the rocking curve is 1.9 to 5.5°.

A piezoelectric film including a piezoelectric body configured to extract radio waves of a required frequency by resonance is provided. The piezoelectric body is based on either of ScAlN or AlN, and an X-ray rocking curve full-width at half-maximum (FWHM) of the piezoelectric body in a lattice plane with a Miller index of (11-20) is not more than 10°.

A piezoelectric device includes a substrate, a diaphragm; and a piezoelectric actuator, in which the substrate, the diaphragm, and the piezoelectric actuator are laminated in this order in a first direction, the diaphragm includes a first layer containing silicon as a constituent element, a third layer disposed between the first layer and the piezoelectric actuator and containing zirconium as a constituent element, and a second layer disposed between the first layer and the third layer and containing at least one impurity element selected from the group consisting of a metal, a metalloid, and a semiconductor other than silicon and zirconium, as a constituent element, and the impurity element diffuses into the third layer.

The diaphragm includes a first layer containing silicon as a constituent element, a third layer disposed between the first layer and the piezoelectric actuator and containing zirconium as a constituent element, and a second layer disposed between the first layer and the third layer and containing at least one selected from the group consisting of a metal other than iron, silicon, and zirconium, a metalloid, and a semiconductor, as a constituent element, in the second layer and the third layer, a position with a highest concentration of impurities other than the constituent elements of the second layer and the third layer is in the second layer, a position with a highest concentration of zirconium is in the third layer, and a position with a highest concentration of silicon is in the first layer.

A physical vapor deposition system includes a deposition chamber, a support to hold a substrate in the deposition chamber, a target in the chamber, a power supply configured to apply power to the target to generate a plasma in the chamber to sputter material from the target onto the substrate to form a piezoelectric layer on the substrate, and a controller configured to cause the power supply to alternate between deposition phases in which the power supply applies power to the target and cooling phases in which power supply does not apply power to the target. Each deposition phase lasts at least 30 seconds and each cooling phase lasts at least 30 seconds.

A method of fabricating a piezoelectric layer includes depositing a piezoelectric material onto a substrate in a first crystallographic phase by physical vapor deposition while the substrate remains at a temperature below 400° C., and thermally annealing the substrate at a temperature above 500° C. to convert the piezoelectric material to a second crystallographic phase. The physical vapor deposition includes sputtering from a target in a plasma deposition chamber.

A method of forming an Al.sub.1-xSc.sub.xN film can include heating a substrate, in a reactor chamber, to a temperature range, providing a precursor comprising Sc to the reactor chamber, providing a dopant comprising Mg, C, and/or Fe to the reactor chamber, and forming an epitaxial Al.sub.1-xSc.sub.xN film on the substrate in the temperature range, the epitaxial Al.sub.1-xSc.sub.xN film including the dopant in a concentration in a range between about 1×10.sup.17/cm.sup.3 and about 2×10.sup.20/cm.sup.3 on the substrate.

A layered structure (100) for transmission of an acoustic wave, the layered structure (100) comprising: a substrate layer (102); and a second layer (104) over the substrate layer (102), wherein the second layer (104) comprises a plurality of discrete portions (105) adjacent to each other, each discrete portion (105) of the plurality of discrete portions (105) comprising a first subregion (104A) and a second subregion (104B). Also an epitaxial layer (108), grown over the second layer (104), for transmission of the acoustic wave in a major plane of the epitaxial layer (108), wherein a periodicity (λ) of a wavelength of the acoustic wave to be transmitted through the epitaxial layer (108) is approximately equal to a sum of a width (d.sub.A) of the first subregion (104A) and a width (d.sub.B) of the second subregion (104B).

A piezoelectric film laminated body includes a metal film, an amorphous film, and a scandium aluminum nitride film. The amorphous film has an insulation property and is disposed on the metal film. The scandium aluminum nitride film is disposed on the amorphous film and is in contact with a surface of the amorphous film.