Trills

Hi all - Can you tell me how to notate a trill? If I have the correct term, I want to notate the for the reader to play the target note but rapidly go up and back down repeatedly by a half step.

Example: Rhythm section plays a C chord but melody plays the note E and goes up to an F and back down rapidly.

See the image of what I want to create (and you can correct me if another form of notation is advisable too if necessary)

Many thanks,