The structure and continuous stoichiometry change of 1DTbBrx@SWCNTs

N A Kiselev; A S Kumskov; V G Zhigalina; A L Vasiliev; J Sloan; N S Falaleev; N I Verbitskiy; A A Eliseev

doi:10.1111/jmi.12348

The structure and continuous stoichiometry change of 1DTbBrx@SWCNTs

J Microsc. 2016 Apr;262(1):92-101. doi: 10.1111/jmi.12348. Epub 2015 Dec 1.

Authors

N A Kiselev¹, A S Kumskov^{1

2

3}, V G Zhigalina^{1

3}, A L Vasiliev^{1

2}, J Sloan⁴, N S Falaleev⁵, N I Verbitskiy^{5

6

7}, A A Eliseev⁵

Affiliations

¹ Electron microscopy laboratory, Shubnikov Institute of Crystallography RAS, Moscow, Russia.
² NBIC Center, NRC 'Kurchatov Institute', Moscow, Russia.
³ Center for surface and vacuum research (CSVR), Moscow, Russia.
⁴ Department of Physics, University of Warwick, Coventry, Warwickshire, U.K.
⁵ Department of Materials Science, Moscow State University, Moscow, Russia.
⁶ Faculty of Physics, University of Vienna, Vienna, Austria.
⁷ Institute of Physics 2, University of Cologne, Cologne, Germany.

PMID: 26625140
DOI: 10.1111/jmi.12348

Abstract

HRTEM and HAADF STEM of 1DTbBrx@SWCNT meta-nanotubes reveal three structural modifications of 1D nanocrystals within single wall carbon nanotube channels attributed to a different stoichiometry of the guest crystal. For SWCNTs with diameters Dm > 1.4 nm a most complete tetragonal unit cell is observed. When crystallization occurs inside SWCNT with Dm < 1.4 nm 1D TbBrx crystal deforms a nanotube to elliptical shape in cross section. In this case the 1D crystal unit cell becomes monoclinic, with possible loss of a part of bromine atoms. Two modifications of a monoclinic unit cell appear. One of them is characterized by single or pair vacancies in the structure of the 1D crystal. Another structure is explained by peripheral and central bromine atoms loss. An appearance of such modifications can be stimulated by electron irradiation. The loss of bromine atoms is in agreement with chemical analysis data. Electronic properties of obtained meta-nanotubes are investigated using optical absorption and Raman spectroscopy. It is shown that intercalation of terbium bromide into SWCNTs leads to acceptor doping of SWCNTs. According to local EDX analysis and elemental mapping this doping can arise from significant stoichiometry change in 1D nanocrystal indicating an average Tb:Br atomic ratio of 1:2.8 ± 0.1.

Keywords: 1DTbBrx@SWCNT; HAADF HRSTEM; HRTEM; SWCNT deformation; acceptor doping; electronic properties; meta-nanotubes; stoichiometry changing; vacancies.

Publication types

Research Support, Non-U.S. Gov't