Microstructural Characterization Of Mgo Thin Films Grown By Radio-Frequency Sputtering. Target And Substrate-Temperature Effect

The microstructure of thin films deposited by radio-frequency (rf)-sputtering on a silicon substrate at several temperatures and with two different targets was investigated by x-ray diffractometry (XRD) and scanning electron microscopy. XRD spectra reveal that films deposited at room temperature from either an MgO or an Mg target contain small (similar to5 nm) periclase MgO crystallites. Thermal treatments in air followed by a fast cooling improved the degree of crystallinity and increased the grain size. The films grown from an Mg target at high temperatures are polycrystalline with a rock-salt structure. However, in thin films deposited from a sintered MgO target at Tgreater than or equal to873 K, the cubic spinel structure due to a mix of periclase (MgO) and brucite [Mg(OH)(2)] is observed; hydrogen comes from the target contamination. Thermal treatments in air at high temperatures improved the degree of crystallinity and texturing. The film structure depends on the cooling rate from elevated temperatures. Nanoindentation measurements yield a hardness value independent of whether the film is amorphous or polycrystalline, and close to the value obtained for bulk MgO single crystals. However, the Young's modulus strongly depends on the atomic structure of the film, being much lower for amorphous films. (C) 2003 American Institute of Physics.