Tungsten phase transformation induced by low-fluence Ar irradiation in CuW multilayers

Abstract

Changes occurring in equiatomic CuW superlattices, prepared by direct sputtering, after low-fluence 300 keV Ar 2+ ion irradiation were investigated by X-ray diffraction. The profiles were measured in θ–2θ geometry. A shift of satellite superlattice peaks to higher 2θ angles was observed for ion doses up to 2 × 10 14 ions/ cm 2. There were no further changes in peak position for higher doses. This effect cannot be interpreted as being caused by an ion mixing process in the copper-tungsten interface regions nor by stress relaxation effects. X-ray diffraction measurements performed on a pure tungsten layer, 1000 Å thick and prepared in the same conditions as the superlattices, revealed the presence of the β-W phase. After 300 keV Ar 2+ ion irradiation with low dose (2 × 10 14 ions/ cm 2), the 110 peak of the α-W structure appeared whereas the 210 peak of the β-W phase disappeared in the X-ray diffraction profile. Thus, during the first stages of irradiation, the transformation from β to α phase occurred in tungsten sublayers.