I am Arun. R. doing M.Sc in Physics(Specialization in Electronics) in India. I am intersted in doing ph.d in Nanotechnology in U.S.A. I have a few questions to ask. a) Is M.S. a must before Ph.D, with my background of B.Sc & M.Sc(Physics) in Physics or can I directly apply for a Ph.D.(If I have a good GRE & TOEFL score.). b) Are there any Ph.D qualifying exam after joining for Ph.D. in U.S. with coursework of 1 year or so. Does it involve any coursework? c) In general, how much time does it take to finish i) Ph.D if applied directly for it ii) M.S. Integerated Ph.D. Thanking you in advance.