Infrared sensor element
View Patent ↗An infrared sensor element according to the present invention includes a substrate, and a lower electrode layer, a pyroelectric layer, and an upper electrode layer sequentially formed on the substrate. The substrate has a linear thermal expansion coefficient higher than that of the pyroelectric layer, and the pyroelectric layer includes a polycrystalline body having an in-plane stress in a compressive direction. Thus, the infrared sensor element realizes the pyroelectric layer having a high orientation in a polarization axis direction, an excellent pyroelectric property.
1. An infrared sensor element comprising:
a substrate;
a lower electrode layer formed on the substrate;
a pyroelectric layer formed on the lower electrode layer; and
an upper electrode layer formed on the pyroelectric layer, wherein
the substrate has a linear thermal expansion coefficient higher than that of the pyroelectric layer, and
the pyroelectric layer is a polycrystalline body having an in-plane compressive stress.
2. The infrared sensor element according to claim 1 , wherein
the lower electrode layer includes a conductive oxide crystalline body.
3. The infrared sensor element according to claim 1 , wherein
the pyroelectric layer is formed by a chemical solution deposition method.
4. The infrared sensor element according to claim 1 , wherein
the substrate has fracture toughness higher than that of the pyroelectric layer.
5. The infrared sensor element according to claim 1 , wherein
the lower electrode layer is a perovskite type.
6. The infrared sensor element according to claim 1 , wherein
a difference between a lattice constant of a main oriented surface of the lower electrode layer and a lattice constant of a main oriented surface of the pyroelectric layer is within ±10%.
7. The infrared sensor element according to claim 1 , wherein
the pyroelectric layer includes a perovskite oxide ferroelectric body provided such that a surface vertical to the substrate is preferentially oriented in a polarization axis direction, and a surface parallel to the substrate is randomly oriented.
8. The infrared sensor element according to claim 1 , wherein
the substrate includes a metal material.
9. The infrared sensor element according to claim 1 , wherein
a highly conductive layer having resistivity lower than that of the lower electrode layer is formed under the lower electrode layer.
10. The infrared sensor element according to claim 1 , wherein
the substrate has a rough surface.
11. The infrared sensor element according to claim 1 , wherein
a surface state of the substrate has a surface roughness Ra of 90 nm or more.
12. The infrared sensor element according to claim 1 , wherein
a pyroelectric layer is further formed on a second surface opposed to a first surface across the substrate having the lower electrode layer, and the pyroelectric layer;
the substrate has a linear thermal expansion coefficient higher than that of the pyroelectric layer on the second surface, and the pyroelectric layer on the second surface includes a polycrystalline body having an in-plane stress.
13. The infrared sensor element according to claim 12 , wherein
the pyroelectric layer on the second surface is formed on the second surface through the lower electrode layer.
14. An infrared sensor element comprising:
a substrate;
a lower electrode layer formed on the substrate;
a pyroelectric layer formed on the lower electrode layer; and
an upper electrode layer formed on the pyroelectric layer, wherein
the substrate has a linear thermal expansion coefficient higher than that of the pyroelectric layer, and
the lower electrode layer is a perovskite type.
15. The infrared sensor element according to claim 14 , wherein
a difference between a lattice constant of a main oriented surface of the lower electrode layer and a lattice constant of a main oriented surface of the pyroelectric layer is within ±10%.
16. The infrared sensor element according to claim 14 , wherein
the pyroelectric layer includes a perovskite oxide ferroelectric body provided such that a surface vertical to the substrate is preferentially oriented in a polarization axis direction, and a surface parallel to the substrate is randomly oriented.
17. An infrared sensor element comprising:
a substrate;
a lower electrode layer formed on the substrate;
a pyroelectric layer formed on the lower electrode layer; and
an upper electrode layer formed on the pyroelectric layer, wherein
the substrate has a linear thermal expansion coefficient higher than that of the pyroelectric layer, and
a difference between a lattice constant of a main oriented surface of the lower electrode layer and a lattice constant of a main oriented surface of the pyroelectric layer is within ±10%.
18. The infrared sensor element according to claim 17 , wherein
the pyroelectric layer includes a perovskite oxide ferroelectric body provided such that a surface vertical to the substrate is preferentially oriented in a polarization axis direction, and a surface parallel to the substrate is randomly oriented.