Structure and secondary electron emission properties of MgO films deposited by pulsed mid-frequency magnetron sputtering

A pulsed mid-frequency magnetron sputtering technique was used to deposit MgO films. Atomic force microscopy, Rutherford backscattering, x-ray diffraction, and a diode discharge device were used to characterize surface morphology, oxygen content, crystalline structure, and the secondary electron emission (gamma) coefficient of the films, respectively. The oxygen content (56 at. %) in all the films remained constant. However, surface morphology, crystalline structure, and the secondary electron emission properties of the films are strongly dependent on the O-2 flow rate. As the O-2 flow rate is increased from 3 to 10 sccm, a sudden decrease in the grain size and the gamma coefficient of the films can be observed, and the crystalline orientation evolves from a strong (200) preferred orientation continuously to a fully (220) preferred orientation. Further increase of O-2 flow rate results in a slight change in the grain size and the crystalline orientation, but a considerable increase in the full width at half maximum of the x-ray diffraction peaks and a significant decrease in the gamma coefficient of the films. We found that preferred orientation and crystalline quality are the main factors that influence the secondary electron emission properties of the MgO films. (C) 2003 American Institute of Physics.