High-k heterostructure

1. A method for preparing a multilayer substrate, comprising the step of deposing an epitaxial γ-Al 2 O 3 Miller index (001) layer less or equal to 3 atomic monolayers thick on a Si Miller index (001) substrate.

2. Method according to claim 1 wherein said epitaxial γ-Al 2 O 3 Miller index (001) layer is deposed using molecular beam epitaxy.

3. Method according to claim 2 wherein the operating temperature, for molecular beam epitaxy, is higher or equal to 850° C.

4. Method according to claim 2 wherein the operating oxygen pressure, for molecular beam epitaxy, is lower or equal to 10 −8 Torr.

5. Method according to claim 1 wherein previous to the deposit of the γ-Al 2 O 3 Miller index (001) layer, the Si substrate is first cleaned in a HF:H 2 O solution, then chemically oxidized in a H 2 SO 4 :H 2 O 2 solution and finally etched in a NH 4 F solution.

6. Method according to claim 1 wherein a dielectric layer, for example a dielectric oxide layer, is deposited on the γ-Al 2 O 3 Miller index (001) layer.

7. Method according to claim 6 , wherein said dielectric layer is deposited on the γ-Al 2 O 3 Miller index (001) layer using molecular beam epitaxy.

8. Method according to claim 6 wherein said dielectric is a high-k oxide.

9. Method according to claim 6 wherein said dielectric is crystalline.

10. Method according to claim 6 wherein said dielectric is Gd 2 O 3 .

11. Method according to claim 6 wherein said dielectric is amorphous.

12. Method according to claim 6 wherein said dielectric layer is deposited at an operating temperature higher or equal to 700° C.

13. Method according to claim 6 wherein said dielectric oxide layer is deposited at an operating oxygen pressure lower or equal to 2×10 −6 Torr.

14. A method, comprising:

depositing a plurality of Miller index (001) Al 2 O 3 monolayers on a Si Miller index (001) substrate layer;

depositing at least one additional Al 2 O 3 monolayer whose Miller index (111) planes align with the Miller index (001) planes of the Si substrate so as to produce a Miller index (111)-oriented Al 2 O 3 lattice.

15. The method of claim 14 , wherein the Miller index (001) Al 2 O 3 monolayers are grown in its cubic y phase on the Si Miller index (001) substrate layer.

16. The method of claim 14 , wherein depositing the plurality of Miller index (001) Al 2 O 3 monolayers comprises depositing only two Miller index (001) Al 2 O 3 monolayers.

17. The method of claim 14 , further comprising depositing a dielectric layer over the Miller index (111)-oriented Al 2 O 3 lattice having a dielectric constant k value greater than or equal to 10.

18. The method of claim 14 , further comprising depositing a dielectric layer over the deposited Al 2 O 3 monolayers.

19. The method of claim 14 , wherein the Al 2 O 3 monolayers are deposited using molecular beam epitaxy.

20. The method of claim 14 , further comprising controlling a growth rate of Al 2 O 3 in situ by using a mass spectrometer.

21. A method, comprising:

depositing a plurality of Miller index (001) Al 2 O 3 monolayers on a Si Miller index (001) substrate layer so as to form an γ-Al 2 O 3 Miller index (001) layer less or equal to 3 atomic monolayers thick; and

depositing a dielectric layer over the γ-Al 2 O 3 Miller index (001) layer.

22. The method of claim 21 , wherein the deposited dielectric layer has a crystalline structure whose Miller index (001) planes are parallel to Miller index (001) planes of the γ-Al 2 O 3 Miller index (001) layer.

23. A method, comprising:

depositing a plurality of Miller index (001) Al 2 O 3 monolayers on a Si Miller index (001) substrate layer so as to form an γ-Al 2 O 3 Miller index (001) layer; and

depositing a dielectric layer over the γ-Al 2 O 3 Miller index (001) layer;

wherein depositing the plurality of Miller index (001) Al 2 O 3 monolayers further comprises depositing at least one additional Al 2 O 3 monolayer whose Miller index (111) planes align with the Miller index (001) planes of the Si substrate so as to produce a Miller index (111)-oriented Al 2 O 3 lattice.

24. The method of claim 21 , wherein depositing the plurality of Miller index (001) Al 2 O 3 monolayers comprises depositing only two Miller index (001) Al 2 O 3 monolayers.

25. The method of claim 21 , wherein the deposited dielectric layer has a dielectric constant k value greater than or equal to 10.

26. The method of claim 21 , wherein the Al 2 O 3 monolayers are deposited using molecular beam epitaxy.

27. The method of claim 21 , further comprising controlling a growth rate of Al 2 O 3 in situ by using a mass spectrometer.