B. Schattat

Ion beam mixing of ZnO/SiO2 and Sb/Ni/Si interfaces under swift heavy ion irradiation

We have investigated the irradiation induced interface mixing in ZnO/SiO2 (α-quartz) and Sb/Ni/Si thin layer systems under swift heavy ion irradiation in the electronic stopping power regime. The irradiations were carried out at 77 K using 100 MeV Ar, 260 MeV Kr, and 200 MeV Xe ions. For the ZnO/SiO2 system experiments were also carried out at lower ion energies (300, 600, and 900 keV, respectively) where nuclear stopping dominates. The alterations of the interface concentration profiles were determined by means of Rutherford backscattering spectrometry performed subsequently at the irradiated and the nonirradiated parts of the samples. While for the semimetal/metal Sb/Ni interface almost no mixing could be found after high-energy irradiation (mixing efficiency for Xe ions: k/Se<0.02 nm5/keV) the ceramic system ZnO/SiO2 strongly reacts upon high energy ion irradiation (Xe: k/Se=2.1 nm5/keV). The Ni/Si interface shows an intermediate effect (Xe: k/Se=0.2 nm5/keV). The mixing behavior found at high ion ener...

Atomic mixing in thin film systems by swift heavy ions

Because of their sensitivity to the electronic energy loss of swift heavy ions, we have investigated the high energy ion beam mixing of oxide layer systems. In this paper we present a summary of the results and first steps towards interpretation and modelling of the observed phenomena. As was also observed in the case of track formation, mixing was found to occur only if the electronic energy loss exceeds a threshold value. The threshold is determined by the less sensitive material, which is a clear hint that both sides of the interface must have been molten, to enable for effective interdiffusion. This interpretation is supported by the estimated interdiffusion constants which indeed lie in the range known for liquid state diffusion.

Atomic transport in hot ion tracks

Abstract In the present paper we will summarize our recent results on swift heavy ion beam mixing (IBM) of oxide ceramics and compare them with the IBM results which where obtained in the nuclear stopping regime. We will show that the strong mixing observed after high energy irradiation is most likely due to the interdiffusion in the molten ion track. The arguments for such a conclusion are based on the fact, that the track formation threshold in both interface forming materials must be exceeded for effective interdiffusion and, even more, that the estimated diffusion constants compare with liquid rather than solid state diffusion. We will show that the “global thermal spike” model, which was developed but failed for mixing in the nuclear stopping regime can be applied for mixing by electronic stopping.

Interface mixing of CuOx/SiO2 bilayers by swift heavy ions

Abstract Thin films of CuOx (x=0, 0.5, 1) on SiO2-substrates were irradiated with heavy ions in the electronic stopping regime (some MeV/amu) and in the nuclear stopping regime (some keV/amu). The irradiation of the oxide layers with Ar, Kr and Xe ions of 90–260 MeV lead to strong interface mixing. The mixing efficiency seems to correlate with the bandgap of the toplayer and the estimation of the effective diffusion constant indicates interdiffusion in molten ion tracks. No mixing was observed after high energy irradiation of Cu/SiO2, which can be explained by the fact that the critical electronic stopping power for track formation has not been exceeded even with 230 MeV Xe ions. Irradiation of CuOx/SiO2 (x=0, 0.5, 1) with 900 keV Xe in all cases leads to only weak intermixing, which can be explained by the ballistic model.

Interface mixing in Ni3N/SiX bilayers induced by swift heavy ions

Abstract In order to investigate the swift heavy-ion-induced mixing of nitride coatings we have irradiated Ni 3 N films on SiO 2 -, Si 3 N 4 -, SiC- and Si-substrates with Ar, Kr, Xe and Au ions of energies ranging from 90 to 350 MeV , for which electronic energy loss dominates. The Ni-concentration profiles at the interfaces before and after irradiation were determined by means of Rutherford backscattering spectrometry with 900 keV He 2+ ions. In all the cases, strong mixing occurred as soon as a material-dependent threshold S ec in the electronic stopping power S e was exceeded. The mixing rate exhibits a squared scaling k= Δ σ 2 /Φ=η 2 (S e −S ec ) 2 and estimation of the effective diffusion constant indicates interdiffusion in molten ion tracks. The threshold value S ec depends on the substrate material and seems to be determined by its melting point and specific heat.