We have investigated the irradiation induced interface mixing in ${\mathrm{ZnO/SiO}}_2$ (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 ${\mathrm{ZnO/SiO}}_2$ 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: ${\mathrm{k/S}}_e\text{<0.02\hspace{0.5em}}{\mathrm{nm}}^5/\mathrm{keV})$ the ceramic system ${\mathrm{ZnO/SiO}}_2$ strongly reacts upon high energy ion irradiation (Xe: ${\mathrm{k/S}}_e\text{=2.1\hspace{0.5em}}{\mathrm{nm}}^5/\mathrm{keV}\mathrm{).}$ The Ni/Si interface shows an intermediate effect (Xe: ${\mathrm{k/S}}_e\text{=0.2\hspace{0.5em}}{\mathrm{nm}}^5/\mathrm{keV}\mathrm{).}$ The mixing behavior found at high ion energies is in contrast to that found in the nuclear stopping regime, where Sb/Ni shows very strong mixing and phase formation while ${\mathrm{ZnO/SiO}}_2$ exhibits only weak ballistic mixing. As was previously observed for the formation of ion tracks, interface mixing due to electronic energy deposition also sets in only if the electronic stopping power exceeds a threshold value.