Effects of Pulsed Electron Beam Irradiation on Al Single Crystal with Pb Overlayers
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EFFECTS OF PULSED ELECTRON BEAM IRRADIATION ON Pb OVERLAYERS
Al SINGLE CRYSTAL WITH
G. BATTAGLIN", A. CARNERA::, L.F. DONA' DALLE ROSE:-, 3 V.N. KULKARNI::, P. MAZZOLDI- , E. D'ANNA::::, G. LEGGIERI"'. AND A. LUCHES":' Unita GNSM-CNR, Dipartimento di Fisica dell'UniversitA, Via Mar zolo 8, 35131 Padova, Italy; Dipartimento di Fisica dell'Universita, Via Arnesano, 73100 Lecce, Italy.
ABSTRACT The effects of pulsed electron beam irradiation (pulse width 50 ns FWHM, electron eneries from 15 to 30 keV and current density in the range of 100 to 2300 A/cm ) on Al-Pb systemsprepared by vacuum evaporation of Pb layers 0 from 500 0A to 2000 A in thickness over Al single crystals have been investigated by Rutherford backscattering (RBS) and scanning electron microscopy. The main effects consist in a Pb loss which shows definite features as a function of the incident beam current density and in a mixing of Pb into Al which is unambiguously detected by a selective chemical etching of Pb still unreacted after irradiation. These experimental results are discussed on the basis of some heat flow model calculations which use Monte-Carlo data for the electron depth dose function.
INTRODUCTION An alternative approach to ion implantation for forming a surface alloy of a given composition is to deposit a thin layer on a proper substrate and then induce an atomic scale mixing between the surface film and the substrate. Such a mixing can be achieved by ion bombardment (ion beam mixing) or by rapid melting and resolidification of the surface [D]. Lasers and electron beams have sufficient power to heat and melt surface layers so rapidly that the bulk temperature is not affected very much. The thermal effects depend mainly on the energy deposition profiles and on the thermophysical properties of the materials. In the case of electron beams the energy deposition in the specimen is deeper and easier to control as compared to laser irradiations. Again, in the case of electron beam the absorbed energy is independent of the state of the sample surface, while for the laser the state of the surface influences the reflectivity and, as a consequence, the absorbed energy. In the present paper we report a study on the Pb-Al system irradiated with high current electron beam pulses (50 ns FWHM duration). The Pb-Al equilibrium phase diagram [2] shows practically no solid solubility of Pb in Al (
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