Microstructure and nanomechanical properties of Al-Mg-B-Ti films synthesized by pulsed laser deposition

Thin films were deposited from an ultra-hard, nanocomposite AlMgB14/TiB2 target on Si (1 0 0) by nanosecond (ns) and femtosecond (fs) pulsed laser deposition (PLD) techniques. X-ray diffraction and transmission electron microscopy were used to determine the film structure; scanning electron microscopy was employed to characterize the film surface topography; and X-ray photoelectron spectroscopy was performed to examine the film compositions and chemical bonding states of constituents. The mechanical properties of thin films such as hardness and elastic modulus were determined by nanoindentation tests. Results showed that the as-deposited films were amorphous, possessing a complex oxide glass structure, and this structure was stable up to 1223 K. The preferential reaction of Al, Mg and B with O inhibits the formation of crystalline AlMgB14. The absence of B-B bonds and nanocrystalline structure leads to nanohardness values for as-deposited films as low as approximately 10 GPa. The intrinsic hardness of the film could not be evaluated exactly because of surface roughness and substrate effects. It was found that the density of particulates in the films was drastically reduced by the use of a fs-pulsed laser source, suggesting that fs-PLD is a potential method for decreasing surface roughness. (C) 2002 Elsevier Science B.V. All rights reserved.