arXiv subjects

Jeremy Sloan

Publications and source records attributed to Jeremy Sloan.

5 recordsLinked to original sources

arXiv2026

Structural properties of one-dimensional $\mathrm{Cs}_2\mathrm{CoCl}_4$ confined within single-walled carbon nanotubes

Crystals under one-dimensional (1D) confinement are well-known to exhibit drastic changes in metallicity, magnetic properties and chemical state, however, the intermediate phase space between binary metal halides and ternary metal halide perovskites remains poorly explored, especially in the context of the rich polymorphism exhibited by both families in the one-dimensional limit. Through aberration-corrected (scanning) transmission electron microscopy and multislice simulations, it is shown that the metal halide $\mathrm{Cs}_2\mathrm{CoCl}_4$ crystallizes in the tetragonal $\wp4/mcc$ and orthorhombic $\wp{mcm}$ rod groups under radial compression within single-walled carbon nanotubes (SWCNTs) of increasingly small diameter, with a massive re-entrant orthorhombic strain towards the $1$ $\mathrm{nm}$ extremum. The persistence of $\mathrm{Co}^{2+}$ is determined from fits to the d.c. magnetization, with a surprisingly small increase in the effective moment ($4.607(3)$ to $4.788(3) \mathit{{\mu}}_\mathrm{B}/\mathrm{f.u.}$) and Weiss constant ($-7.9(3)$ to $-4.09(7) \mathrm{K}$) after confinement in the SWCNTs, suggesting that the confined structure topologically preserves the core magnetic properties of the bulk. Both unconventional polymorphs observed are noticeably different to the high-pressure piezochromic polymorph previously shown to undergo a tetrahedral-to-octahedral coordination transition, highlighting 1D confinement as a unique tool for structural manipulation.

cond-mat.mtrl-sci↗

arXiv2020

Exit Wavefunction Reconstruction from Single Transmission Electron Micrographs with Deep Learning

Half of wavefunction information is undetected by conventional transmission electron microscopy (CTEM) as only the intensity, and not the phase, of an image is recorded. Following successful applications of deep learning to optical hologram phase recovery, we have developed neural networks to recover phases from CTEM intensities for new datasets containing 98340 exit wavefunctions. Wavefunctions were simulated with clTEM multislice propagation for 12789 materials from the Crystallography Open Database. Our networks can recover 224x224 wavefunctions in ~25 ms for a large range of physical hyperparameters and materials, and we demonstrate that performance improves as the distribution of wavefunctions is restricted. Phase recovery with deep learning overcomes the limitations of traditional methods: it is live, not susceptible to distortions, does not require microscope modification or multiple images, and can be applied to any imaging regime. This paper introduces multiple approaches to CTEM phase recovery with deep learning, and is intended to establish starting points to be improved upon by future research. Source code and links to our new datasets and pre-trained models are available at https://github.com/Jeffrey-Ede/one-shot

eess.IV↗

arXiv2017

Single-Atom Scale Structural Selectivity in Te Nanowires Encapsulated inside Ultra-Narrow, Single-Walled Carbon Nanotubes

Extreme nanowires (ENs) represent the ultimate class of crystals: They are the smallest possible periodic materials. With atom-wide motifs repeated in one dimension (1D), they offer a privileged perspective into the Physics and Chemistry of low-dimensional systems. Single-walled carbon nanotubes (SWCNTs) provide ideal environments for the creation of such materials. Here we present a comprehensive study of Te ENs encapsulated inside ultra- narrow SWCNTs with diameters between 0.7 nm and 1.1 nm. We combine state-of-the-art imaging techniques and 1D-adapted ab initio structure prediction to treat both confinement and periodicity effects. The studied Te ENs adopt a variety of structures, exhibiting a true 1D realisation of a Peierls structural distortion and transition from metallic to insulating behaviour as a function of encapsulating diameter. We analyse the mechanical stability of the encapsulated ENs and show that nanoconfinement is not only a useful means to produce ENs, but may actually be necessary, in some cases, to prevent them from disintegrating. The ability to control functional properties of these ENs with confinement has numerous applications in future device technologies, and we anticipate that our study will set the basic paradigm to be adopted in the characterisation and understanding of such systems.

cond-mat.mtrl-sci↗

arXiv2017

Encapsulated Nanowires: Boosting Electronic Transport in Carbon Nanotubes

The electrical conductivity of metallic carbon nanotubes (CNTs) quickly saturates with respect to bias voltage due to scattering from a large population of optical phonons. Decay of these dominant scatterers in pristine CNTs is too slow to offset an increased generation rate at high voltage bias. We demonstrate from first principles that encapsulation of 1D atomic chains within a single-walled CNT can enhance decay of "hot" phonons by providing additional channels for thermalisation. Pacification of the phonon population growth reduces electrical resistivity of metallic CNTs by 51% for an example system with encapsulated beryllium.

cond-mat.mtrl-sci↗

arXiv2014

Atomically Resolved Imaging of Highly Ordered Alternating Fluorinated Graphene

One of the most desirable goals of graphene research is to produce ordered 2D chemical derivatives of suitable quality for monolayer device fabrication. Here we reveal, by focal series exit wave reconstruction, that C2F chair is a stable graphene derivative and demonstrates pristine long-range order limited only by the size of a functionalized domain. Focal series of images of graphene and C2F chair formed by reaction with XeF2 were obtained at 80 kV in an aberration-corrected transmission electron microscope. EWR images reveal that single carbon atoms and carbon-fluorine pairs in C2F chair alternate strictly over domain sizes of at least 150 nm^2 with electron diffraction indicating ordered domains >/= 0.16 square micrometer. Our results also indicate that, within an ordered domain, functionalization occurs on one side only as theory predicts. Additionally we show that electron diffraction provides a quick and easy method for distinguishing between graphene, C2F chair and fully fluorinated stoichiometric CF 2D phases.

cond-mat.mtrl-sci↗