Processing of hollow micro- and nanostructures using the hydrophilic nature of MgO

We show that covering the water-saturated MgO surface with an Al2O3 film using atomic layer deposition and then annealing it at 400 °C leads to plastic deformation of alumina by trapped water vapor with consequent development of hollow structures. This phenomenon is applied to thin films, nanopatterned surfaces and isolated 3D nanostructures.