Formation of SiGe nanotubes

1. A method for forming nanotubes on a buried insulator, the method comprising the steps of:

forming one or more fins in a silicon-on-insulator (SOI) layer of an SOI wafer, wherein the SOI wafer has a substrate separated from the SOI layer by the buried insulator;

forming a silicon germanium (SiGe) layer on the fins;

annealing the SiGe layer under conditions sufficient to drive-in germanium (Ge) from the SiGe layer into the fins and form a SiGe shell completely surrounding each of the fins; and

removing the fins selective to the SiGe shell, wherein the SiGe shell which remains forms the nanotubes on the buried insulator.

2. The method of claim 1 , wherein the SiGe layer comprises epitaxial SiGe, the method further comprising the step of:

growing the SiGe layer on the fins.

3. The method of claim 1 , wherein the conformal SiGe layer has a thickness T of from about 1 nanometers (nm) to about 100 nm, and ranges therebetween.

4. The method of claim 1 , wherein the conditions comprise a temperature of from about 400° C. to about 1200° C., and ranges therebetween.

5. The method of claim 1 , wherein the conditions comprise a duration of from about 1 millisecond to about 60 minutes, and ranges therebetween.

6. The method of claim 1 , wherein the annealing is performed in the presence of a gas selected from the group consisting of: oxygen (O 2 ), hydrogen (H 2 ), nitrogen (N 2 ), argon (Ar), helium (He), and combinations thereof.

7. The method of claim 1 , further comprising the step of:

burying the fins in a dielectric material before the annealing.

8. The method of claim 7 , wherein the dielectric material comprises an oxide material.

9. The method of claim 7 , further comprising the step of:

removing the dielectric material before removing the remaining portions of the fins selective to the SiGe shell.

10. The method of claim 1 , wherein the remaining portions of the fins are removed selective to the SiGe shell using a silicon-selective wet etch with an aqueous solution containing ammonia.

11. A device comprising one or more nanotubes on a buried insulator prepared by the method of claim 1 .

12. The nanotube device of claim 11 , wherein each of the nanotubes comprises two sides having a length x and two sides having a length y, wherein x=y.

13. The nanotube device of claim 11 , wherein each of the nanotubes comprises two sides having a length x and two sides having a length y, wherein x>y.

14. The nanotube device of claim 11 , wherein the nanotube device comprises a sensor, the nanotube device further comprising:

contacts to opposite ends of at least one of the nanotubes.

15. A method of forming a nanotube device, the method comprising the steps of:

forming one or more fins in a SOI layer of an SOI wafer, wherein the SOI wafer has a substrate separated from the SOI layer by a buried insulator;

forming a SiGe layer on the fins;

annealing the SiGe layer under conditions sufficient to drive-in Ge from the SiGe layer into the fins and form a SiGe shell completely surrounding each of the fins;

removing the fins selective to the SiGe shell, wherein the SiGe shell which remains forms the nanotubes on the buried insulator; and

forming contacts to opposite ends of at least one of the nanotubes.

16. The method of claim 15 , wherein the conditions comprise a temperature of from about 400° C. to about 1200° C., and ranges therebetween.

17. The method of claim 15 , wherein the conditions comprise a duration of from about 1 millisecond to about 60 minutes, and ranges therebetween.

18. The method of claim 15 , wherein the annealing is performed in the presence of a gas selected from the group consisting of: O 2 , H 2 , N 2 , Ar, He, and combinations thereof.

19. The method of claim 15 , further comprising the steps of:

burying the fins in a dielectric material before the annealing; and

removing the dielectric material before removing the remaining portions of the fins selective to the SiGe shell.

20. A nanotube device prepared by the method of claim 15 .