Credit: Image courtesy of Guangwen Zhou
Hydrogen caused oxygen atoms to go missing at a buried interface of a copper oxide, Cu2O, island on metallic copper (Cu). This caused the island to rotate when it transformed to metal. (a) The hydrogen gas (H2, atoms are green) reacted with the oxygen in the oxide, forming water (H2O) that was released from the surface. (b) The departing oxygen atoms left behind vacancies in the oxide. (c) The oxygen vacancies (cyan) moved through the oxide layer and accumulated at the interface. (d) The entire oxide island rotated because of the tilted interface.