The stage ii recovery behavior of a series of ion-irradiated platinum (gold) alloys as studied by field-ion microscopy

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Abstract
Direct and visible evidence has been obtained for long-range migration of self-interstitial atoms (SIAs) in Stage II of three different ion-irradiated platinum (gold) alloys. Field-ion microscope (FIM) specimens of Pt-0.10, 0.62 and 4.0 at.% Au alloys were irradiated in situ with 30 keV W+ or Pt+ ions at a tip temperature of 35 to 41 K at 2 × 10−9 torr. Direct observation of the surfaces of the FIM specimens during isochronal warming experiments to 100 K showed that a flux of SIAs crossed the specimens' surfaces between 40 to 100 K. The spectrum for each alloy consisted of two recovery peaks (substages IIB and IIC).The results are explained on the basis of an impurity-delayed diffusion mechanism employing a two-level trapping model. The application of this diffusion model to the isochronal recovery spectra yielded a dissocation enthalpy (δh diss li-Au) and an effective diffusion coefficient for each substage; for substage IIB δh diss li-Au (IIB) = 0.15 eV for substage IIC δh diss li-Au (IIC) = 0.24 eV. A series of detailed control experiments were also performed to show that the imaging electric field had not caused the observed long-range migration of SIAs and that the observed effects were not the result of surface artifacts.