On this page of our game guide to Batman: Arkham Knight we explain how to surrender to Scarecrow. It's a mandatory step in the game's ending and you can't omit it in any way.
After you leave the movie studio, wait until Oracle contacts Batman and go to the marked building in Kingston district. Once you reach it, enter the building and reach the room with large amount of screens. Now listen to Scarecrow's instructions and interact with the table in order to leave the utility belt on it. Now you can go to the truck parked nearby and sit inside.