Experimental evidence of crystalline hillocks created by irradiation of CeO₂with swift heavy ions: TEM study

Abstract

In this study, CeO2 was irradiated with 200 MeV Au ions at oblique incidence. Observation of as-irradiated samples by transmission electron microscopy (TEM) shows that hillocks are created not only at the wide surfaces, but also at the crack faces of the thin samples. Since the hillocks created at the crack faces can be imaged by TEM, their shape and crystallographic features can be revealed. From the images of hillocks created at the crack faces, many of the hillocks are found to be spherical. We present the first experimental evidence that hillocks created for CeO2 irradiated with swift heavy ions have a crystal structure whose lattice spacing and orientation coincide with those of the matrix. The mechanism of spherical crystalline hillock formation is discussed based on the present results.

Near surface latent track morphology of SHI irradiated TiO2

“…BF TEM micrographs from Ref. of 200 MeV Au irradiated CeO 2 also display signs of near surface conicity. Their specimens were thinned prior to irradiation and subtle double conical shapes can be discerned for the ion tracks connecting the spherical hillocks on the top and bottom surface of the specimens.…”

“…The first reported direct TEM observation of surface hillocks was performed on CeO 2 by Ref. . Prior to this report, surface hillocks were characterized mainly by AFM .…”

“…In this work, we use an alternative approach to that of Ref. to prepare TEM specimens for hillock observation. The focussed ion beam (FIB) based technique has the advantage of being compatible with both bulk crystals and pre‐thinned material although the amorphous carbon coating used in the FIB technique does reduce lattice contrast during the TEM observation of the hillocks somewhat.…”

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 .…”

FE-SEM observations of multiple nanohillocks on SrTiO₃ irradiated with swift heavy ions

“…The formation of nanostructures in ceramics upon irradiation with swift heavy ions is interesting not only from a technological perspective but also from the viewpoint of the physics of ion-solid interactions. It is well known that swift heavy ions can create nanosized hillocks on the surfaces of various ceramics, such as calcium fluoride (CaF2) [1,2], cerium oxide (CeO2) [3,4], and strontium titanate (SrTiO3) [5,6]. When these materials are irradiated with swift heavy ions at normal incidence, each ion impact results in the formation of a single hillock.…”