Microstructure and stability of the deposited beta-uranium films

Abstract

Uranium films have important applications in inertial confinement fusion (ICF) research and other fields. The stability of crystal structure/microstructure is an essential factor restricting its application. In this study, pure uranium films with the stable beta phase structure at room temperature have been prepared by magnetron sputtering. The results of Auger analysis show that the main component of the film is metallic uranium. The content of C, O and other impurity elements is lower than the detection limit of the instrument. The phase and texture were analyzed by X-ray diffraction. It is confirmed that the film is completely composed of beta phase uranium. And the sample has a very sharp (002) plane fiber texture. The surface and section morphology of the film illustrates that the size of columnar grain is tens of nm. The residual stress in the film was measured by substrate curvature method. The result shows that there is a compressive stress of more than 1 GPa. The storage experiment at room temperature indicates that the phase, grain size, texture and residual stress of the uranium film remain unchanged after one year, which confirms the stability of the sample. And then, the growth mode of uranium films and the reason of its stability were discussed.