Thermally stimulated solid state reactions in Fe–Al multilayers prepared by pulsed laser deposition

Abstract

Two 15-period Fe–Al multilayers (single layer thicknesses ∼5 nm Al and ∼2 nm Fe) prepared by direct and crossed-beam pulsed laser deposition (DPLD and CBPLD, respectively) were subjected to annealing between 50 and 950°C. Phase analysis done by X-ray diffraction and determination of layer morphology using X-ray reflectometry showed that solid state reaction kinetics is different in DPLD and CBPLD samples. This applies in particular to the sequence of intermetallic compounds formed as well as to the temperatures of full intermixing. Pronounced interdiffusion of Fe and Al starts at annealing temperatures of about 110 –140°C and a full intermixing of multilayer material occurs at temperatures between 250°C (DPLD) and 300°C (CBPLD). The difference in kinetics between CBPLD and DPLD samples is due to a difference in the structure of interfaces and in their average chemical composition.