Electrically tunable device and a method relating thereto
First Claim
1. A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure, and an electrode structure, wherein the ferroelectric layer structure includes a number of ferroelectric layers and a number of intermediate buffer layers arranged in an alternating manner, and at least a first and a second of the ferroelectric layers have different Curie temperatures, whereby the dielectric constant of the first ferroelectric layer has a maximum at a temperature which is different than the temperature at which the dielectric constant of the second ferroelectric layer has a maximum, wherein all layers have lattice matched crystal structures.
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Abstract
A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure and an electrode structure is presented. The ferroelectric layer structure comprises a number of ferroelectric layers and a number of intermediate buffer layers arranged in an alternating manner. At least a first and a second layer of the ferroelectric layers have different Curie temperatures, i.e. the dielectric constant of the first ferroelectric layer has a maximum at a temperature which is different from the temperature at which the dielectric constant of the second ferroelectric layer has a maximum.
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Citations
18 Claims
- 1. A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure, and an electrode structure, wherein the ferroelectric layer structure includes a number of ferroelectric layers and a number of intermediate buffer layers arranged in an alternating manner, and at least a first and a second of the ferroelectric layers have different Curie temperatures, whereby the dielectric constant of the first ferroelectric layer has a maximum at a temperature which is different than the temperature at which the dielectric constant of the second ferroelectric layer has a maximum, wherein all layers have lattice matched crystal structures.
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8. A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure, and an electrode structure, wherein the ferroelectric layer structure includes a number of ferroelectric layers and a number of intermediate buffer layers arranged in an alternating manner, and at least a first and a second of the ferroelectric layers have different Curie temperatures, whereby the dielectric constant of the first ferroelectric layer has a maximum at a temperature which is different than the temperature at which the dielectric constant of the second ferroelectric layer has a maximum, wherein the ferroelectric layers comprise ceramic materials, and wherein the ceramic material(s) comprise perovskite oxides of the formula RxR′
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1-xR″
O3, wherein R and R′
are independently selected from a group of elements consisting of Group I and Group II metals of the Periodic Table of Elements and R″
is selected from a group of elements consisting of Group IV and Group V metals of the Periodic Table of Elements, wherein each ferroelectric layer has an elemental composition of BaxiSr1-xiTiO3 respectively, wherein the content x~ is different for at least two ferroelectric layers to produce different Curie temperatures for said at least two ferroelectric layers. - View Dependent Claims (9)
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1-xR″
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10. A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure, and an electrode structure, wherein the ferroelectric layer structure includes a number of ferroelectric layers and a number of intermediate buffer layers arranged in an alternating manner, and at least a first and a second of the ferroelectric layers have different Curie temperatures, whereby the dielectric constant of the first ferroelectric layer has a maximum at a temperature which is different than the temperature at which the dielectric constant of the second ferroelectric layer has a maximum, wherein the ferroelectric layers comprise ceramic materials, and wherein the ceramic material(s) comprise perovskite oxides of the formula RxR′
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1-xR″
O3, wherein R and R′
are independently selected from a group of elements consisting of Group I and Group II metals of the Periodic Table of Elements and R″
is selected from a group of elements consisting of Group IV and Group V metals of the Periodic Table of Elements, wherein the ferroelectric layers comprise NaxiK1-xiNbO3 respectively, wherein the content xi is different for at least two ferroelectric layers to produce different Curie temperatures. - View Dependent Claims (15)
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1-xR″
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11. A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure, and an electrode structure, wherein the ferroelectric layer structure includes a number of ferroelectric layers and a number of intermediate buffer layers arranged in an alternating manner, and at least a first and a second of the ferroelectric layers have different Curie temperatures, whereby the dielectric constant of the first ferroelectric layer has a maximum at a temperature which is different than the temperature at which the dielectric constant of the second ferroelectric layer has a maximum, wherein the intermediate buffer layers comprise dielectric films, and wherein at least one of the dielectric film layers has an elemental composition of one of MgO, LaAlO3, and CeO2.
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12. A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure, and an electrode structure, wherein the ferroelectric layer structure includes a number of ferroelectric layers and a number of intermediate buffer layers arranged in an alternating manner, and at least a first and a second of the ferroelectric layers have different Curie temperatures, whereby the dielectric constant of the first ferroelectric layer has a maximum at a temperature which is different than the temperature at which the dielectric constant of the second ferroelectric layer has a maximum, wherein the intermediate buffer layers comprise dielectric films, and wherein at least one of the dielectric film layers has an elemental composition of WO3.
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13. A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure, and an electrode structure, wherein the ferroelectric layer structure includes a number of ferroelectric layers and a number of intermediate buffer layers arranged in an alternating manner, and at least a first and a second of the ferroelectric layers have different Curie temperatures, whereby the dielectric constant of the first ferroelectric layer has a maximum at a temperature which is different than the temperature at which the dielectric constant of the second ferroelectric layer has a maximum, wherein at least one of the intermediate buffer layers comprises a multilayer structure comprising a number of sublayers wherein at least one sublayer has an elemental composition of MgO and at least one sublayer has an elemental composition of WO3.
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14. A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure, and an electrode structure, wherein the ferroelectric layer structure includes a number of ferroelectric layers and a number of intermediate buffer layers arranged in an alternating manner, and at least a first and a second of the ferroelectric layers have different Curie temperatures, whereby the dielectric constant of the first ferroelectric layer has a maximum at a temperature which is different than the temperature at which the dielectric constant of the second ferroelectric layer has a maximum, wherein the ferroelectric layer structure comprises at least three ferroelectric layers.
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16. A thin film ferroelectric varactor device comprising a substrate layer, a ferroelectric layer structure, and an electrode structure, wherein the ferroelectric layer structure comprises a number of ferroelectric layers and a number of intermediate buffer layers that form dielectric layers, the ferroelectric layers and the dielectric layers being arranged in an alternating manner such that ferroelectric layers between which an intermediate buffer layer is provided are chemically separated from each other and have a different elemental composition such that the temperature dependence of the dielectric constants of the respective layers is different, wherein the ferroelectric layers comprise ceramic materials such as perovskite oxides of the type RxR′
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1-xR″
O3 wherein xi is different for at least subsequent ferroelectric layers between which an intermediate buffer layer is arranged, and wherein for each ferroelectric layer, i, xi is in the range 0≦
xi≦
1, wherein i=1, . . . , N, with N being the number of ferroelectric layers, and wherein the ferroelectric layers i, wherein i=1, . . . N, with N being the number of layers, are one of Baxi Sr1-xi TiO3 and NAxi K1-xiNbO3. - View Dependent Claims (17, 18)
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1-xR″
Specification