Piezoelectric thin film element and piezoelectric thin film device using a piezoelectric thin film of alkali-niobium oxide series
To provide a piezoelectric thin film on a substrate, having an alkali-niobium oxide-based perovskite structure expressed by a composition formula (K 1-x Na x ) y NbO 3 , wherein the composition ratio x of the piezoelectric thin film expressed by (K 1-x Na x ) y NbO 3 is in a range of 0.4≦x≦0.7, and a half width of a rocking curve of (001) plane by X-ray diffraction measurement is in a range of 0.5° or more and 2.5° or less.
1. A piezoelectric thin film element, comprising:
a piezoelectric thin film on a substrate, having an alkali-niobium oxide-based perovskite structure expressed by a composition formula (K 1-x Na x ) y NbO 3 ,
wherein the composition ratio x of the piezoelectric thin film expressed by (K 1-x Na x ) y NbO 3 is in a range of 0.4≦x≦0.7, and a half width of a rocking curve of (001) plane by X-ray diffraction measurement is in a range of 0.5° or more and 2.5° or less.
2. The piezoelectric thin film element according to claim 1 , wherein the piezoelectric thin film has a pseudo-cubic crystal structure.
3. The piezoelectric thin film element according to claim 1 , wherein the piezoelectric thin film has a pseudo-cubic crystal structure, and is preferentially oriented to (001) plane direction.
4. The piezoelectric thin film element according to claim 1 , wherein a composition ratio (K+Na)/Nb of the piezoelectric thin film is in a range of 0.7 or more and 0.94 or less.
5. The piezoelectric thin film element according to claim 1 , comprising:
a lower electrode at the substrate side of the piezoelectric thin film; and
an upper electrode at an opposite side to the substrate of the piezoelectric thin film.
6. The piezoelectric thin film element according to claim 5 , wherein the lower electrode is made of platinum, and is preferentially oriented to (111) plane direction.
7. A piezoelectric thin film device, comprising:
a lower electrode provided on a substrate;
a piezoelectric thin film provided on the lower electrode, having an alkali-niobium oxide-based perovskite structure expressed by a composition formula (K 1-x Na x ) y NbO 3 , with the composition ratio x being in a range of 0.4≦x≦0.7, and a half width of a rocking curve of (001) plane by X-ray diffraction measurement being in a range of 0.5° or more and 2.5° or less;
an upper electrode provided on the piezoelectric thin film; and
a function generator or a voltage detection unit connected between the lower electrode and the upper electrode.