Piezoelectric stack, piezoelectric element, and method of manufacturing piezoelectric stack
There is provided a piezoelectric stack, including: a substrate; an oxide film on the substrate, containing zinc and oxygen as main elements; an electrode film on the oxide film; and a piezoelectric film on the electrode film, being an alkali niobium oxide film containing potassium, sodium, niobium, and oxygen and having a perovskite structure.
1 . A piezoelectric stack comprising:
a substrate;
an oxide film on the substrate, containing zinc and oxygen as main elements;
an electrode film on the oxide film; and
a piezoelectric film on the electrode film, being an alkali niobium oxide film containing potassium, sodium, niobium, and oxygen and having a perovskite structure,
wherein crystals constituting the oxide film are preferentially oriented in (0001) direction.
2 . The piezoelectric stack according to claim 1 , wherein a (001) orientation ratio of crystals constituting the piezoelectric film is 80% or more.
3 . The piezoelectric stack according to claim 2 , wherein a relative dielectric constant of the piezoelectric film is 250 or more and 300 or less when measured by applying a voltage of −1 V to +1 V to a top electrode film being a film on the piezoelectric film and different from the electrode film, with a triangular wave having a frequency of 3 kHz while the electrode film is grounded.
4 . The piezoelectric stack according to claim 2 , wherein a thickness of the oxide film is 1 nm or more.
5 . The piezoelectric stack according to claim 2 , further comprising a top electrode film, being an electrode film different from the electrode film, on the piezoelectric film.
6 . The piezoelectric stack according to claim 1 , wherein a (001) orientation ratio of crystals constituting the piezoelectric film is 90% or more.
7 . The piezoelectric stack according to claim 6 , wherein a relative dielectric constant of the piezoelectric film is 250 or more and 300 or less when measured by applying a voltage of −1 V to +1 V to a top electrode film being a film on the piezoelectric film and different from the electrode film, with a triangular wave having a frequency of 3 kHz while the electrode film is grounded.
8 . The piezoelectric stack according to claim 6 , wherein a thickness of the oxide film is 1 nm or more.
9 . The piezoelectric stack according to claim 6 , further comprising a top electrode film, being an electrode film different from the electrode film, on the piezoelectric film.
10 . The piezoelectric stack according to claim 1 , wherein a relative dielectric constant of the piezoelectric film is 250 or more and 300 or less when measured by applying a voltage of −1 V to +1 V to a top electrode film being a film on the piezoelectric film and different from the electrode film, with a triangular wave having a frequency of 3 kHz while the electrode film is grounded.
11 . The piezoelectric stack according to claim 10 , wherein a thickness of the oxide film is 1 nm or more.
12 . The piezoelectric stack according to claim 1 , wherein a thickness of the oxide film is 1 nm or more.
13 . The piezoelectric stack according to claim 1 , further comprising a top electrode film, being an electrode film different from the electrode film, on the piezoelectric film.
14 . A piezoelectric element comprising:
a substrate;
an oxide film on the substrate, containing zinc and oxygen as main elements;
a bottom electrode film on the oxide film;
a piezoelectric film on the bottom electrode film, being an alkali niobium oxide film containing potassium, sodium, niobium, and oxygen and having a perovskite structure; and
a top electrode film on the piezoelectric film,
wherein crystals constituting the oxide film are preferentially oriented in (0001) direction.
15 . The piezoelectric element according to claim 14 , wherein a (001) orientation ratio of crystals constituting the piezoelectric film is 80% or more.
16 . The piezoelectric element according to claim 14 , wherein when a positive voltage is applied at a temperature of 200° C., to the top electrode film such that an electric field of 300 kV/cm is generated between the top electrode film and the bottom electrode film, it takes 1500 seconds or more, from a start of the voltage application until a density of a leakage current flowing through the piezoelectric film exceeds 30 mA/cm 2 .
17 . The piezoelectric element according to claim 14 , wherein a (001) orientation ratio of crystals constituting the piezoelectric film is 90% or more.
18 . The piezoelectric element according to claim 17 , wherein when a positive voltage is applied at a temperature of 200° C., to the top electrode film such that an electric field of 300 kV/cm is generated between the top electrode film and the bottom electrode film, it takes 1800 seconds or more, from a start of the voltage application until a density of a leakage current flowing through the piezoelectric film exceeds 30 mA/cm 2 .
19 . A method of manufacturing a piezoelectric stack, comprising:
depositing an oxide film on a substrate, containing zinc and oxygen as main elements;
depositing an electrode film on the oxide film; and
depositing a piezoelectric film on the electrode film, being an alkali niobium oxide film containing potassium, sodium, niobium, and oxygen and having a perovskite structure,
wherein crystals constituting the deposited oxide film are preferentially oriented in (0001) direction.
20 . The method of manufacturing a piezoelectric stack according to claim 19 , wherein in the deposition of the oxide film, the oxide film is deposited under a temperature condition of 200° C. or more, and
in the deposition of the electrode film, the electrode film is deposited under a temperature condition of 200° C. or more.