D.D.
If this is the job you want you need to send a handwritten thank you note to the interviewer now! It doesn't have to say much, you can even use a thank you note card (professional looking one) and write in there that you'd like to say thankyou for their time and the information they gave you and that you are looking forward to an opportunity to work with such a great company.
If they are on the fence about you, a thank you note can push them over enough to get you back in there for a 2nd interview and give you another chance to wow them.
Good luck.