Fabrication of piezoelectric device with PMNPT layer

1 . A piezoelectric device, comprising:

a substrate;

a thermal oxide layer on a surface of the substrate;

a metal adhesion layer on the thermal oxide layer, wherein the metal adhesion layer consists of metallic chromium, metallic nickel, or a metallic alloy of chromium and nickel;

a lower electrode on the metal adhesion layer on the thermal oxide layer, wherein the metal adhesion layer and the lower electrode are composed of different materials;

a seed layer on the lower electrode, wherein the seed layer is titanium oxide or niobium oxide;

a lead magnesium niobate-lead titanate (PMNPT) piezoelectric layer on the seed layer,

wherein the PMNPT piezoelectric layer is composed of columnar grains of <001> crystallographic orientation with respect to the surface of the substrate; and

an upper electrode on the PMNPT piezoelectric layer.

2 . The piezoelectric device of claim 1 , wherein the substrate comprises a silicon substrate and the thermal oxide layer is silicon oxide.

3 . The piezoelectric device of claim 1 , wherein the lower electrode is composed of platinum.

4 . The piezoelectric device of claim 1 , wherein the PMNPT piezoelectric layer is composed of (1-x)[Pb(Mg 1/3 Nb 2/3 )O 3 ]-x[PbTiO 3 ], where x is about 0.2 to 0.8, and y is about 0.8 to 0.2.

5 . The piezoelectric device of claim 3 , wherein the upper electrode has a same composition as the lower electrode.

6 . A method of fabricating a piezoelectric device, comprising:

forming, on a surface of a substrate, an adhesion layer on a thermal layer of the substrate by depositing metallic titanium, metallic chromium, metallic nickel, or a metallic combination thereof;

depositing a lower electrode on the adhesion layer, wherein the adhesion layer and the lower electrode are composed of different materials;

forming a seed layer on the lower electrode, wherein the seed layer is titanium oxide or niobium oxide;

depositing a lead magnesium niobate-lead titanate (PMNPT) piezoelectric layer on the seed layer by physical vapor deposition, wherein PMNPT piezoelectric layer is composed of columnar grains of <001> crystallographic orientation with respect to the surface of the substrate after deposition; and

depositing an upper electrode on the PMNPT piezoelectric layer.

7 . The method of claim 6 , comprising depositing the adhesion layer with the substrate at 20-25° C.

8 . The method of claim 6 , wherein forming the seed layer includes depositing a metal layer and annealing the substrate to convert at least a portion of the metal layer to a metal oxide seed layer.

9 . The method of claim 8 , wherein forming the adhesion layer, depositing the lower electrode and forming the seed layer comprise physical vapor depositions.

10 . The method of claim 6 , wherein forming the adhesion layer comprises forming a metal layer.

11 . A piezoelectric device, comprising:

a single crystal silicon wafer having a <001> crystallographic orientation with respect to a surface of the single crystal silicon wafer;

a silicon oxide layer on the single crystal silicon wafer;

a titanium oxide adhesion layer on the silicon oxide layer, the titanium oxide adhesion layer having a thickness of 25-40 nm;

a platinum lower electrode of <111> crystallographic orientation on the titanium oxide adhesion layer;

a seed layer on the platinum lower electrode, the seed layer consisting of titanium oxide and having a thickness of 1-5 nm;

a lead magnesium niobate-lead titanate (PMNPT) piezoelectric layer of <001> crystallographic orientation with respect to the surface of the single crystal silicon wafer on the seed layer; and

a platinum upper electrode with a first surface contacting the PMNPT piezoelectric layer,

wherein a second surface of the platinum upper electrode opposite the first surface is an exposed surface of the piezoelectric device.

12 . The piezoelectric device of claim 11 , wherein the silicon oxide layer directly contacts the single crystal silicon wafer.