10 research outputs found
Stable CoO Nanoscrolls With Outstanding Electrical Properties
Layered CoO is of great interest for its promising properties but is
meta-stable in its bulk form. CoO was synthesized in a long-term stable
nanotubular or scrolled form by converting the quasi-one-dimensional crystal
structure of bulk CaCoO via a hydrothermal treatment. The resulting
one-dimensional nanostructures with very thin walls are investigated in detail.
The CoO_ is found to crystallize in monoclinic form, similar to the related
CaCoO-CoO misfit structure. Individual nanoscrolls are characterized
electrically and show a p-type semiconducting nature with a high
current-carrying capacity of A/cm and an extremely high
breakdown voltage of 27 kV/cm. The results demonstrate the possibility to
stabilize meta-stable materials in low-dimensional forms and a promising
application of the nanoscrolls as interconnect in high-voltage electronic
circuitry
Strontium-deficient SrxCoO2-CoO2 nanotubes as a high ampacity and high conductivity material
Continuous miniaturization of electronics demands the development of interconnectors with high ampacity and high conductivity, which conventional conductors such as copper and gold cannot offer. Here we report the synthesis of Sr-deficient misfit SrxCoO2–CoO2 nanotubes by a novel crystal conversion method and investigate their electrical properties. Bulk Sr6Co5O15 having a quasi-one-dimensional CoO6 polyhedral structure (face-sharing octahedron and trigonal prismatic CoO6 arranged in one-dimension) is converted to SrxCoO2–CoO2 nanotubes where CoO2 adopts a two-dimensional edge-sharing CoO2 layered structure in a basic hydrothermal process. Electrical properties measured on individual nanotubes demonstrate that these nanotubes are semiconducting with a conductivity of 1.28 × 104 S cm−1 and an ampacity of 109 A cm−2, which is the highest reported ampacity value to date of any inorganic oxide-based material. The nanotubes also show a breakdown power per unit channel length (P/L) of ∼38.3 W cm−1, the highest among the regularly used interconnect materials. The above results demonstrate that SrxCoO2–CoO2 nanotubes are potential building blocks for high-power electronic applications.Prof. L.S.P. would like to acknowledge Science and Engineering Research Board under the Department of Science and Technology (DST-SERB), Government of India for funding (EMR/2016/003594). K.S.R. acknowledges the Department of Chemistry, Department of Physics and Department of Materials Engineering and Materials Science, Indian Institute of Technology (IIT) Bombay and Industrial Research and Consultancy Center (IRCC), Sophisticated Analytical Instrument Facility (SAIF), Centre of Excellence in Nanoelectronics (CEN) IIT Bombay and Fund for Improvement of S&T Infrastructure (FIST) for all the facilities provided. K.S.R. sincerely thanks Gayatri Vaidya at IIT Bombay for helpful assistance and discussion about the fabrication process. S.H. and R.A. acknowledge funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 889546 and from the Spanish MICINN (project grant PID2019-104739GB-100/AEI/10.13039/501100011033). R. A. acknowledges funding from the Government of Aragon (project DGA E13-20R) and European Union H2020 program “ESTEEM3” (823717).Peer reviewe
Atomic Structural Studies on Thin Single-Crystalline Misfit-Layered Nanotubes of TbS-CrS<sub>2</sub>
Various nanotubes
from ternary misfit compounds have been reported
in recent years. In the present work, the detailed atomic structure
and chemical configuration of misfit-layered nanotubes based on the
TbS-CrS<sub>2</sub> are reported. These analyses have been developed
via different transmission electron microscopy techniques, including
high-resolution scanning transmission electron microscopy, electron
diffraction, and electron energy loss spectroscopy. These structural
analyses show that two different kinds of nanotubes can be produced:
a “regular” nanotube and a “wavy” one.
Both kinds of nanotubes show the alternating arrangements of the TbS
and CrS<sub>2</sub> subsystems; however, the wavy ones present a nearly
periodically deficiency in terbium. In addition to the structural
investigation, the chemical analyses have proved that the outer layer
of both kinds of nanotubes is composed of the elements Cr and S. All
these findings helped to understand the growth mechanism during the
sulfurization reaction taking place in the synthesis process
Nanotubes from Oxide-Based Misfit Family: The Case of Calcium Cobalt Oxide
Misfit
layered compounds (MLCs) have generated significant interest
in recent years as potential thermoelectric materials. MLC nanotubes
could reveal behavior that is entirely different from the bulk material.
Recently, new chemical strategies were exploited for the synthesis
of nanotubular forms of chalcogenide-based MLCs, which are promising
candidates for thermoelectric materials. However, analogous synthesis
of oxide-based MLC nanotubes has not been demonstrated until now.
Here, we report a chemical strategy for synthesis of cobalt-oxide-based
misfit nanotubes. A combination of high-resolution (scanning) transmission
electron microscopy (including image simulations), spatially resolved
electron energy-loss spectroscopy, electron diffraction, and density
functional theory (DFT) calculations is used to discover the formation
of a phase within these nanotubes that differs significantly from
bulk calcium cobaltite MLCs. Furthermore, DFT calculations show that
this phase is semiconducting with a band gap in excess of 1 eV, unlike
bulk calcium cobaltite MLCs, which are known to be metallic. Through
systematic experiments, we propose a formation mechanism for these
nanotubes that could also apply more generally to realizing other
oxide-based MLC nanotubes
Strontium Cobalt Oxide Misfit Nanotubes
Low-dimensional
misfit layered compounds have been found to have ultralow thermal
conductivity, which is attributed to their unique structure and the
low dimensionality. There are a few studies reporting the preparation
of sulfide-based misfit nanotubes but only one study on oxide-based
analogs. In this investigation, we report a new oxide-based misfit
nanotube derived from misfit layered strontium cobaltite. Thorough
structural investigation by electron microscopy techniques, including
electron diffraction, aberration corrected high-resolution (scanning)
transmission electron microscopy, and electron energy-loss spectroscopy
along with density functional theory calculations show that these
nanotubes consist of alternating layers of SrCoO<sub>2</sub> and CoO<sub>2</sub>. We have studied systematically the effect of base concentration
on the structure and composition of the nanotubes, which reveals the
importance of misfit stress to tightly roll the structure into tubular
form and thus control the synthesis. Electronic structure calculations
find that the structures are semiconducting with a ferrimagnetic ground
state. Our studies further extend the family of bulk misfit layered
oxides into the 1D realm with potential applications in thermoelectric
and electronic devices
Atomic Structural Studies on Thin Single-Crystalline Misfit-Layered Nanotubes of TbS-CrS 2
Nanotubes from Misfit Layered Compounds: A New Family of Materials with Low Dimensionality
Nanotubes that are formed from layered materials have emerged to be exciting one-dimensional materials in the last two decades due to their remarkable structures and properties. Misfit layered compounds (MLC) can be produced from alternating assemblies of two different molecular slabs with different periodicities with the general formula [(MX)1+x]m[TX2]n (or more simply MS-TS2), where M is Sn, Pb, Bi, Sb, rare earths, T is Sn, Nb, Ta, Ti, V, Cr, and so on, and X is S, Se. The presence of misfit stresses between adjacent layers in MLC provides a driving force for curling of the layers that acts in addition to the elimination of dangling bonds. The combination of these two independent forces leads to the synthesis of misfit layered nanotubes, which are newcomers to the broad field of one-dimensional nanostructures and nanotubes. The synthesis, characterization, and microscopic details of misfit layered nanotubes are discussed, and directions for future research are presente