Hi Nibedita,

Top 10 IIT For Phd are:-

1-IIT Bombay.

2-IIS Banglore.

3-IIT Madras.

4-IIT Delhi.

5-IIT Kharagpur.

6-IIT Kanpur.

7-University of Hyderabad.

8-Universisty of Delhi.

9-IIT Roorkee.

10-IIT Guwahati.

Phd are of two types:-

i) Regular Phd.(After Masters)

ii) Integrated Phd.[After Graduation(Masters+Ph.d)

Exams for Regular Phd:- GATE JRF, TIFR,UGC NET JRF,CSIR NET JRF,etc.

Exams for Integrated Phd:-IIT JAM,Gate,etc.

Hope this will help please feel free to ask if you have any further queries.

Thank you.