Near surface latent track morphology of SHI irradiated TiO₂

Abstract

The material response to SHI irradiation of simple oxides such as TiO 2 is markedly different in the near surface volume than in the bulk. In this subsurface region, several tens of nanometers in thickness, the material exhibits a much higher sensitivity to damage creation. The enhanced sensitivity of the material in this region is related to the proximity of a free surface and not strongly dependent on electronic stopping power. At least for these materials, the assumption of cylindrical latent tracks is dubious and great care should be taken when inferring track Phys.

Simulation of Two-Dimensional Images for Ion-Irradiation Induced Change in Lattice Structures and Magnetic States in Oxides by Using Monte Carlo Method

“…The above model that TiO 2 sample is amorphized only inside the ion -track, and the amorphized region never contributes to the XRD diffraction seems to be too simple. The previous TEM (transmission electron microscope) observations, however, clearly show that just inside the ion-track in TiO 2 , the structure becomes amorphous, and outside the iontrack, the crystal structure is maintained [26,27]. The XRD peaks for TiO 2 samples which are almost completely amorphized by high energy heavy ion irradiation are much smaller than for the unirradiated crystalline TiO 2 and are scarcely observed [22].…”

Overview of SHI Induced Track Morphology in Crystalline Non-Metals from Direct Observation with TEM

“…Indirect methods such as the Rutherford backscattering in channelling configuration (RBS-C) can infer "effective" diameters by assuming the total measured disorder in the probed layer is the sum of identical cylindrical tracks but this assumption is clearly not valid for these materials. Also, it has been shown previously that the near surface regions of these materials exhibit significantly different track morphology than in the bulk [14].…”

Fine structure of swift heavy ion track in rutile TiO2

“…However, this model cannot explain why track morphology changes from an cylinder to a cone as a function of ion path length in the same thickness of thin sample as shown in Fig. 2a 21,24 , as they are all defined as non-amorphizable materials (or "resistant materials" in some literature) 30,59,60 .…”

“…A reduced internal pressure near surface of rutile has been suggested to be responsible for the formation of conical morphology of ion track 24 . However, this model cannot explain why track morphology changes from an cylinder to a cone as a function of ion path length in the same thickness of thin sample as shown in Fig.…”

“…Hillocks on the surface of specimen, after bombarded with swift heavy ions under normal or grazing incidence angle, were observed by AFM and scanning electron microscopy [37][38][39][40][41] . More recently, the conical tracks consist of an agglomeration of 1-2 nm sized features near surface of rutile, was observed by TEM 23,24 . As the detailed morphology and structure of irradiation-induced damage along the entire length of ion tracks has not been revealed, the reduced internal pressure near surface of rutile has been considered responsible for the formation of conical morphology of ion track 24 .…”