Ph.D

Now, there is one more course called direct Ph.D which most of the students didn't know about. Direct Ph.D is the course which you can directly do after B.Tech/be degree. The admission for direct Ph.D is same as MS admission and it is now there in all NITs/IITs. In the respective IITs, you can fill the form and they will call you for the interview and written test and based on your performance you will get the college. The interview is related to basic maths and basic knowledge of subjects. In direct Ph.D also you can go for the interdisciplinary branch as it will be helpful in future. In direct Ph.D, you have to do coursework more as compared to regular Ph.D (after M.Tech) but you will save 2 years of M.Tech by taking admission in direct Ph.D and you will get more stipend as compared to MS/M.Tech.
Note: Prefer old IITs for direct Ph.D course as you will get more exposure more learning. For direct Ph.D there is one more option called conversion from M.Tech/MS programme to Ph.D. In this, if you join in any of the IITs/NITs for M.Tech/MS programme after completion of 1-year you can convert to direct Ph.D (CGPA required: 8.0 in 1st year) and you will start getting more stipend of INR 25000. If you will take admission in IIT Madras as a direct Ph.D, you will get 2 degrees after finishing i.e. MS+Ph.D.

Hi Sravya,
You have to research on the NET looking for universities offering Ph.D. in this field. Ph.D. admissions are bit different and requires that you must first be accepted by a supervisor. You are advised to check university websites and search for your concerned department's information, research supervisor, formalities etc. Email them about your interests, cite them your publications, papers, research proposal, etc.
It is also recommended that you share some letters of recommendation from professors to build your network. Some universities may require the GRE. You have to check these on university websites. University of Guelph, University of Waterloo, etc. are some considerations.