After Msc ?

I'm not quite sure I understand you. You say you want to do an Mtech, which I think is an undergraduate Masters in Engineering. Where are you from?

If you know you want to research then it'd probably be best to choose an MSc course that is more specific and geared to that research area than just 'Physics'. In the UK at least, the Physics MSc courses are more geared to undergraduates from other disciplines and want to transfer over.

I.e. if you want to go into Astronomy, look at an Astronomy MSc. If you want to go into Nanoscience, look at a Nanoscience MSc. If you're not sure about what kind of research you want to go into then now is the time to have a good long think. Each field you go into has a plethora of different research topics and it will take a long time to narrow down to the final level but it would be a good start to choose a general subject area now.