In Situ Electron Beam Amorphization of Sb₂Te₃ within Single Walled Carbon Nanotubes

Abstract

In this study, we reveal the crystallography, crystallinity, and amorphization of low-dimensional crystals of the topological insulator and phase change material Sb2Te3 within both discrete and bundled single walled carbon nanotubes with a diameter range spanning 1.3-1.7 nm by a combination of electron diffraction, aberration-corrected high resolution imaging, and variable dose electron beam irradiation. We further reveal that electron diffraction indicates that the crystallinity of the host single walled carbon nanotubes is largely unaffected by this process indicating that mass loss during the observed in situ glass transition had not occurred and that the template had maintained its structural integrity. Such a transition would not be possible with any other common nanoporous template for which the pores would be enlarged due to likely sintering.

Unprecedented New Crystalline Forms of SnSe in Narrow to Medium Diameter Carbon Nanotubes

“…Extreme nanowires and encapsulated nanomaterials have recently garnered significant interest, particularly in relation to the use of very narrow single-walled carbon nanotubes (SWCNTs) as confining templates. − The resulting encapsulation engenders modification to the properties of the host SWCNTs but also profound alteration of the properties of the embedded nanowires, as a consequence of nanostructuring imposed by the latter. The van der Waals forces at the internal surfaces of the SWCNTs constrain the encapsulated material to cross sections as small as ≃1 nm 2 , resulting in structures that are completely different to the bulk form of the material, , producing unprecedented new nanostructured crystalline forms. These can be observed experimentally but also anticipated by predictive modeling methods including molecular dynamics (MD), − density functional theory (DFT), , and ab initio random structure searching (AIRSS). − Both experimentation and theoretical modeling are making significant headway in terms of measuring and predicting new functionality of novel nanostructured crystalline forms including modified phonon optics, anticipated band gap modification but, most recently, potentiation of thermoelectric properties in the smallest crystalline forms, prompting new studies into similar materials and other phenomena on a similar scale including electrochemical reactivity …”

“…Prolonged exposure of the filled SWCNTs to the electron beam has also been shown to have potentially beneficial modifying effects on certain nC-fillings, such as amorphization of Sb 2 Te 3 within SWCNTs . Providing the energy of the electron beam is maintained below 80 kV, the filling can then be modified without electron beam knock-on damage to the SWCNT.…”

“…2−4 The resulting encapsulation engenders modification to the properties of the host SWCNTs but also profound alteration of the properties of the embedded nanowires, as a consequence of nanostructuring imposed by the latter. The van der Waals forces at the internal surfaces of the SWCNTs constrain the encapsulated material to cross sections as small as ≃1 nm 2 , resulting in structures that are completely different to the bulk form of the material, 5,6 producing unprecedented new nanostructured crystalline forms. These can be observed experimentally but also anticipated by predictive modeling methods including molecular dynamics (MD), 7−10 density functional theory (DFT), 11,12 and ab initio random structure searching (AIRSS).…”

“…37,38 Prolonged exposure of the filled SWCNTs to the electron beam has also been shown to have potentially beneficial modifying effects on certain nC-fillings, such as amorphization of Sb 2 Te 3 within SWCNTs. 5 Providing the energy of the electron beam is maintained below 80 kV, the filling can then be modified without electron beam knock-on damage to the SWCNT. Some extraneous materials in compositional analysis measurements can be attributed to the procedure for synthesizing the SWCNTs, which includes the use of Co, Mo, and a supporting catalyst.…”