I also struggle with the same problems as the original poster since 90% of my shifts are at night. One thing that helped me is reverse the alarm clock: instead of setting the alarm clock to wake up, I set it to go to sleep. As soon as my alarm goes, I don't touch any ipad or things that can keep me alert. Otherwise I will find myself staying up later and later because I don't feel sleepy yet. A second thing that helped me is getting every bit of rest I can at nightshifts, even for 5 minutes or so, instead of going to the coffee machine or checking the emails again.