Your deaf student may support his or her face-to-face communication with you by writing and/or by asking you to write. This strategy can be a useful one to support clear communication.
However, it is important to be clear that this strategy is not always useful or successful for all deaf people. Elsewhere on this site you will find information about the English literacy difficulties faced by some deaf people. You will need to be mindful of this and assess whether or not writing notes will be a feasible option.
If your deaf student does have English literacy challenges [see more], then it is often best to keep written notes simple. A good guide is to write sentences in a way similar to how s/he writes.
The best thing to do is to talk this option through with your deaf student, asking him or her if writing is an option to support communication between the two of you.