Piezoelectric thin film and piezoelectric vibrator
A piezoelectric film that includes crystalline AlN; at least one first element partially replacing Al in the crystalline AlN; and a second element doping the crystalline AlN and which has an ionic radius smaller than that of the first element and larger than that of Al.
1. A piezoelectric film comprising:
crystalline AlN;
at least one first element partially replacing Al in the crystalline AlN; and
a second element doping the crystalline AlN, the second element being a trivalent cation having a coordination number of 4 or 6, and having an ionic radius smaller than an ionic radius of the first element and larger than an ionic radius of Al.
2. The piezoelectric film according to claim 1 , wherein the first element is Sc.
3. The piezoelectric film according to claim 2 , wherein a ratio of a number of Sc atoms to a total number of Al and Sc atoms is 0.03 to 0.50 in the piezoelectric film.
4. The piezoelectric film according to claim 1 , wherein the at least one first element comprises a Group 3 element, Group 2 and 4 elements, Group 2 and 5 elements, Group 12 and 4 elements, or Group 12 and 5 elements.
5. The piezoelectric film according to claim 1 , wherein a percentage ratio of a number of atoms of the second element to a total number of Al atoms and atoms of the first element is 0.01 at % to 1.00 at %.
6. A piezoelectric vibrator comprising:
a first electrode;
a second electrode;
a piezoelectric film between the first and second electrodes,
the piezoelectric film comprising:
crystalline AlN;
at least one first element partially replacing Al in the crystalline AlN; and
a second element doping the crystalline AlN, the second element being a trivalent cation having a coordination number of 4 or 6, and having an ionic radius smaller than an ionic radius of the first element and larger than an ionic radius of Al.
7. The piezoelectric vibrator according to claim 6 , wherein the first element is Sc.
8. The piezoelectric vibrator according to claim 7 , wherein a ratio of a number of Sc atoms to a total number of Al and Sc atoms is 0.03 to 0.50 in the piezoelectric film.
9. The piezoelectric vibrator according to claim 6 , wherein the at least one first element comprises a Group 3 element, Group 2 and 4 elements, Group 2 and 5 elements, Group 12 and 4 elements, or Group 12 and 5 elements.
10. The piezoelectric vibrator according to claim 6 , wherein a percentage ratio of a number of atoms of the second element to a total number of Al atoms and atoms of the first element is 0.01 at % to 1.00 at %.