Microstructure of β-FeSi2 thin films prepared by pulsed laser deposition

Iron disilicide thin films were prepared by pulsed laser deposition (PLD) on Si (100) substrates using a FeSi2 alloy target. Droplet-free films could be deposited at a fluence between 2 and 4 J/cm(2) using a 193-nm laser. Polycrystalline films of beta -FeSi2 phase could be formed even at a substrate temperature of 20 degreesC. In addition to the beta -FcSi(2) phase, the FeSi phase was observed for substrate temperatures between 400 and 600 degreesC. This is attributed to the mobility enhancement of Si atoms. At 700 degreesC, the FeSi phase disappeared and beta -FeSi2 single-phase films having a columnar structure were grown due to the mobility enhancement of both the Fe and Si atoms. At the substrate temperatures of less than 600 degreesC, the lattices of beta -FeSi2 were distorted. At substrate temperatures higher than 700 degreesC, the lattice constants approached the bulk values. The films deposited at more than 700 degreesC were grown epitaxially on Si(100) with the relation of beta -FeSi2 (041) or (014) II Si (220) at the beginning of deposition. As the film thickness increases, the epitaxial growth becomes disordered and finally becomes non-oriented near the film surface. For all films deposited at various substrate temperatures, the stoichiometry was constant in the depth direction. Thus, it is suggested that Si atoms from the substrate hardly diffused into the film. The generation of iron disilicide in the PLD deposition mechanism is also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.