I/We claim:
1. A method for fabricating a nano-sensor comprising:
patterning a sensing electrode assembly on a sacrificial layer of a substrate, wherein the sensing electrode assembly comprises a pair of contact pads and an electrode element coupled to and disposed between the pair of contact pads;
forming the sensing electrode assembly based on the patterning;
removing the sacrificial layer below a portion of the electrode element to obtain a suspended electrode element; and
oxidizing the suspended electrode element at a first predetermined temperature to obtain a pair of electromigrated regions and a notch portion between the pair of the electromigrated regions, wherein the notch portion is to detect a gaseous component in an ambient gas at a second predetermined temperature.
2. The method as claimed in claim 1 comprising depositing the sacrificial layer over
the substrate, wherein:
the sacrificial layer is a semiconductor selected from the group consisting of silicon dioxide and silicon nitride; and
the substrate is a semiconductor selected from the group consisting of silicon, ceramic, and plastic.
3. The method as claimed in claim 2, wherein a thickness of the sacrificial layer is in a range of 10 nm to 100 nm and a thickness of the substrate is in a range of 50 urn to 500 Hm.
4. The method as claimed in claim 1, wherein the patterning is by Electron Beam Lithography and forming is by Direct Current Sputtering.

5. The method as claimed in claim 1, wherein removing the sacrificial layer is by etching.
6. The method as claimed in claim 1, wherein the first predetermined temperature is in a range of 600-800° C.
7. The method as claimed in claim 1, wherein the second predetermined temperature is inarangeof20-50°C.
8. The method as claimed in claim 1, wherein the sensing electrode assembly is fabricated from metal selected from the group consisting of tungsten, nickel, palladium, titanium, and platinum.
9. The method as claimed in claim 1, wherein the oxidizing comprises:
providing a potential difference between the pair of contact pads for a predetermined time to heat the electrode element to the first predetermined temperature to obtain the pair of electromigrated regions and the notch portion between the electromigrated regions; and
exposing the electrode element to rich oxygen ambient to oxidize the electrode element.
10. A method for fabricating a nano-sensor array comprising:
patterning a sensing electrode assembly on a sacrificial layer of a substrate, wherein the sensing electrode assembly comprises a pair of common contact pads and a plurality of electrode elements coupled to and disposed between the pair of common contact pads;
forming the sensing electrode assembly based on the patterning;

removing the sacrificial layer below a portion of each of the plurality of electrode elements to obtain a plurality of suspended electrode elements; and
applying a potential difference between the pair of contact pads to oxidize the plurality of suspended electrode elements at a first predetermined temperature to obtain a pair of electromigrated regions on each suspended electrode element and a notch portion between the pair of the electromigrated regions, wherein the notch portion is to detect a gaseous component in an ambient gas at a second predetermined temperature.
11. The method as claimed in claim 10 comprising depositing the sacrificial layer over
the substrate, wherein:
the sacrificial layer is a semiconductor selected from the group consisting of silicon dioxide and silicon nitride; and
the substrate is a semiconductor selected from the group consisting of silicon, ceramic, and plastic.
12. The method as claimed in claim 11, wherein a thickness of the sacrificial layer is in a range of 10 nm to 100 nm and a thickness of the substrate is in a range of 50 um to 500 um.
13. The method as claimed in claim 10, wherein the patterning is by Electron Beam Lithography and forming is by Direct Current Sputtering.
14. The method as claimed in claim 10, wherein removing the sacrificial layer is by etching.
15. The method as claimed in claim 10, wherein the first predetermined temperature is inarangeof600-800°C.

16. The method as claimed in claim 10, wherein the second predetermined temperature is in a range of 20 - 50° C.
17. The method as claimed in claim 10, wherein the sensing electrode assembly is fabricated from metal selected from the group consisting of tungsten, nickel, palladium, titanium, and platinum.
18. A nano-sensor comprising:
a sensing electrode assembly formed on a sacrificial layer comprising a pair of contact pads and a suspended electrode element coupled to and disposed between the pair of contact pads, wherein the suspended electrode element comprises:
a pair of electromigrated regions and a notch portion between each
electromigrated region of the pair of the electromigrated regions, wherein the
notch portion is to detect a gaseous component in an ambient gas at a second
predetermined temperature.
19. The nano-sensor as claimed in claim 18, wherein the notch portion comprises a first
core enclosed within a first shell, wherein:
the first core is formed from metal selected from the group consisting of tungsten, nickel, palladium, titanium, and platinum, wherein the first core has a thickness in a range of 1-60 nanometres; and
the first shell is formed from a metal oxide of the first core, wherein the first shell has a thickness in a range of 1 - 60 nm.
20. The nano-sensor as claimed in claim 18, wherein a length of the notch portion
between the pair of electromigrated regions is in a range of 100 - 300 nm.

21. The nano-sensor as claimed in claim 19, wherein each electromigrated region of
the pair of electromigrated region comprises a second core enclosed within a second
shell, wherein:
the second core is formed from the metal of the first core, wherein the second core has a thickness in a range of 1 - 60 nanometres; and
the second shell is formed from the metal oxide of the second core, wherein the second shell has a thickness in a range of 1 -60 nanometres.
22. A nano-sensor array comprising a plurality of nano-sensors as claimed any of
claims 18-21.