In situ real-time analysis of the formation of a quasicrystalline phase inAl-Co multilayers by solid-state reaction

An in situ analysis of the reactions involved in the formation of decagonal Al-Co films was performed using the synchrotron radiation at ESRF taking a dvantage of the high-flux source and the fast detection system. The samples are Al/Co multilayers deposited by successive electron-beam evaporations o f elements. The total thickness is 300 nm with a period of 60 nm and a glob al atomic composition of 13Al/4Co. From the initial stage of elements, the formation of the decagonal phase proceeds in three steps; the last one is t he growth of the decagonal phase through a peritectoid reaction between Al9 CO2 and Co. X-ray patterns were obtained following scanning and isothermal heating modes. The results obtained in the scanning mode are in very good a greement with those obtained recently by differential scanning calorimetry, ramped resistance measurements and post mortem X-ray diffraction (XRD). Fr om isothermal anneals carried out at given temperature we characterize the kinetics of each reaction step including the growth of the quasicrystalline phase. (C) 2001 Elsevier Science B.V. All rights reserved.