Abstract
It has been known that the modification of non-metallic solid materials (oxides, nitrides, etc.), e.g., the formation of tracks, sputtering representing atomic displacement near the surface and lattice disordering are induced by electronic excitation under high-energy ion impact. We have investigated lattice disordering by the X-ray diffraction (XRD) of SiO2, ZnO, Fe2O3 and TiN films and have also measured the sputtering yields of TiN for a comparison of lattice disordering with sputtering. We find that both the degradation of the XRD intensity per unit ion fluence and the sputtering yields follow the power-law of the electronic stopping power and that these exponents are larger than unity. The exponents for the XRD degradation and sputtering are found to be comparable. These results imply that similar mechanisms are responsible for the lattice disordering and electronic sputtering. A mechanism of electron–lattice coupling, i.e., the energy transfer from the electronic system into the lattice, is discussed based on a crude estimation of atomic displacement due to Coulomb repulsion during the short neutralization time (~fs) in the ionized region. The bandgap scheme or exciton model is examined.
Highlights
IntroductionAmorphization has been observed for crystalline SiO2 [5] and the Al2O3 surface at a high ion fluence (though the X-ray diffraction (XRD) peak remains) by Ohkubo et al [24] and Grygiel et al [25]
Material modification induced by electronic excitation under high-energy (> 0.1 MeV/u) ion impact has been observed for many non-metallic solids since the late 1950’s; for example, the formation of tracks in LiF crystal by Young [1], in mica by Silk et al [2], in SiO2-quartz, crystalline mica, amorphous P-doped V2O5, etc. (TEM) by Fleischer et al [3,4], in oxides (SiO2-quartz, Al2O3, ZrSi2O4, Y3Fe5O12, high-Tc superconducting copper oxides, etc.) (TEM) by Meftah et al [5] and Toulemonde et al [6], in Al2O3 crystal by
It is found that lattice disordering is caused by electronic excitation and the degradation of the X-ray diffraction (XRD)
Summary
Amorphization has been observed for crystalline SiO2 [5] and the Al2O3 surface at a high ion fluence (though the XRD peak remains) by Ohkubo et al [24] and Grygiel et al [25]. I.e., a lower density in the track core surrounded by a shell with a higher density, has been observed for Al2O3 [10], amorphous SiO2 [11], Si3N4 [14] and amorphous SiN0.95:H and SiO1.85:H [16]. An electrically conducting track formation in tetrahedralamorphous carbon (sp into sp bond transformation) has been observed by Gupta et al [29].
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