Hi Aspirant,

Yes you can persue Mtech in nano Technology after you btech irrespective of the branch.

Admission into this course can be obtained by appearing for entrance exam like GATE.

There are many IITs, NITS  and many universities provide this two years course.

Here are few IITs and NITs that provide Mtech in nano Technology :-

1.IIT-Delhi, Guwahati, Roorkee, Chennai, Kanpur, Mumbai.

2.Jawaharlal Nehru Center for Advanced Scientific Research

3.National Institute of Technology

4.Vellore Institute of Technology

5.Anna University

You can refer this link for more information :-

https://engineering.careers360.com/colleges/list-of-me-mtech-in-nano-technology-engineering-colleges-in-andhra-pradesh

Hope this helps!