Publications by authors named "Pierce Maguire"

Helium ion irradiation is a known method of tuning the electrical conductivity and charge carrier mobility of novel two-dimensional semiconductors. Here, we report a systematic study of the electrical performance of chemically synthesized monolayer molybdenum disulfide (MoS) field-effect transistors irradiated with a focused helium ion beam as a function of increasing areal irradiation coverage. We determine an optimal coverage range of approx.

View Article and Find Full Text PDF

Two-dimensional (2D) layered semiconductors have recently emerged as attractive building blocks for next-generation low-power nonvolatile memories. However, challenges remain in the controllable fabrication of bipolar resistive switching circuit components from these materials. Here, the experimental realization of lateral memtransistors from monolayer single-crystal molybdenum disulfide (MoS) utilizing a focused helium ion beam is reported.

View Article and Find Full Text PDF

Precise tunability of electronic properties of two-dimensional (2D) nanomaterials is a key goal of current research in this field of materials science. Chemical modification of layered transition metal dichalcogenides leads to the creation of heterostructures of low-dimensional variants of these materials. In particular, the effect of oxygen-containing plasma treatment on molybdenum disulfide (MoS) has long been thought to be detrimental to the electrical performance of the material.

View Article and Find Full Text PDF

Using state-of-the-art atomic scale super energy dispersive X-ray spectroscopy and high angle annular dark field imaging this study reveals the elemental partitioning preference between the γ' and γ phases in a Co-Al-W-Ti-Ta superalloy and the site preference of its alloying elements in the ordered L1 γ' phase. A semi-quantitative analysis of atomic column compositions in the ordered L1 γ' structure is provided. Co atoms were found to occupy the {1/2, 1/2, 0} face-center positions whereas Al, W, Ti and Ta atoms prefer to occupy the {0, 0, 0} cube corner positions in the L1 γ phase.

View Article and Find Full Text PDF

In this study, an in vitro Caco-2 cell culture assay was employed to evaluate the correlation between emulsion structure and cellular uptake of encapsulated β-carotene. After 4 h of incubation, an emulsion stabilized with whey protein isolate showed the highest intracellular accumulation of β-carotene (1.06 μg), followed by that stabilized with sodium caseinate (0.

View Article and Find Full Text PDF

Nanoceria (i.e., CeO nanoparticles) fuel additives have been used in Europe and elsewhere to improve fuel efficiency.

View Article and Find Full Text PDF

A focused helium ion beam was used to introduce nano-sized gap chains in graphene. The effect of beam scanning strategies in the fabrication of the nano-gap chains was investigated. The tuning of graphene conductivity has been achieved by modulating the magnitude and uniformity of the ion dose and hence the morphology of the nano-gap chains.

View Article and Find Full Text PDF

A flexible and efficient method to fabricate nanopores in graphene has been developed. A focused, low-energy (5 keV) electron beam was used to locally activate etching of a graphene surface in a low pressure (0.3 Pa) N2 environment.

View Article and Find Full Text PDF

Two-dimensional (2D) materials usually have a layer-dependent work function, which require fast and accurate detection for the evaluation of their device performance. A detection technique with high throughput and high spatial resolution has not yet been explored. Using a scanning electron microscope, we have developed and implemented a quantitative analytical technique which allows effective extraction of the work function of graphene.

View Article and Find Full Text PDF

Cobalt hydrate and doped binary Co0.9M0.1OOH (M = Ni, Mn, Fe) nanorings of 100-300 nm were fabricated in solution through a facile ambient oxidation method.

View Article and Find Full Text PDF

Recently, significant attention has been paid to the resistance switching (RS) behaviour in Fe3O4 and it was explained through the analogy of the electrically driven metal-insulator transition based on the quantum tunneling theory. Here, we propose a method to experimentally support this explanation and provide a way to tune the critical switching parameter by introducing self-aligned localized impurities through the growth of Fe3O4 thin films on stepped SrTiO3 substrates. Anisotropic behavior in the RS was observed, where a lower switching voltage in the range of 10(4) V cm(-1) is required to switch Fe3O4 from a high conducting state to a low conducting state when the electrical field is applied along the steps.

View Article and Find Full Text PDF

We report subnanometer modification enabled by an ultrafine helium ion beam. By adjusting ion dose and the beam profile, structural defects were controllably introduced in a few-layer molybdenum disulfide (MoS2) sample and its stoichiometry was modified by preferential sputtering of sulfur at a few-nanometer scale. Localized tuning of the resistivity of MoS2 was demonstrated and semiconducting, metallic-like, or insulating material was obtained by irradiation with different doses of He(+).

View Article and Find Full Text PDF

Surface organic residues inhibit the extraordinary electronic properties of graphene, hindering the development of graphene electronics. However, fundamental understanding of the residue morphology is still absent due to a lack of high-throughput and high-resolution surface characterization methods. Here, we demonstrate that secondary electron (SE) imaging in the scanning electron microscope (SEM) and helium ion microscope (HIM) can provide sub-nanometer information of a graphene surface and reveal the morphology of surface contaminants.

View Article and Find Full Text PDF