NanoSQUIDS incorporating nanobridges as the Josephson element are desirable since their small dimensions mean they can be situated in close proximity to very small, highly localised magnetic moments for high spin sensitivity. Key to achieving the necessary dimensions are the lithographic technologies used to fabricate the nanobridges. Here we present characterisation of Nb nanoSQUIDs incorporating nanobridges fabricated by three different techniques: neon focused ion beam (FIB) lithography, gallium FIB lithography and e-beam lithography (EBL). We discuss the critical currents and voltage-current characteristics achieved by each technique at various temperatures for a range of nanobridge widths, and discuss the corresponding nanoSQUID voltage modulation and potential applications.

For the prosthetic retina, a device replacing dysfunctional cones and rods, with the ability to mimic the spectral response properties of these photoreceptors and provide electrical stimulation signals to activate residual visual pathways, can relay sufficient data to the brain for interpretation as color vision. Organic semiconductors including conjugated polymers with four different bandgaps providing wavelength‐specific electrical responses are ideal candidates for potential full‐color vision restoration. Here, conjugated polymer photocapacitor devices immersed in electrolyte are demonstrated to elicit a photovoltage measured by a Ag/AgCl electrode 100 microns from the device of ≈−40 mV for 15–39 µW mm−2 of incident light power density at three wavelengths: 405 nm for blue photoreceptor candidate material, 534 nm for green, 634 nm for red. Photoresponse is substantially improved by introducing polymer donor/acceptor molecules bulk heterojunctions. Devices with bulk heterojunction configurations achieved at least −70 mV for green candidates with the highest at −200 mV for red cone candidates. These findings highlight the potential for organic materials to bridge the gap toward natural vision restoration for retinal dystrophic conditions such as age‐related macular degeneration, Stargardt disease, or retinitis pigmentosa and contribute to the ongoing advancements in visual prosthetic devices.

Niobium nanobridge SQUIDs have shown exceptional noise performance with potential applications in quantum information processing, weak signal detection and single spin detection where the nanobridge geometry should enable efficient electromagnetic coupling to implanted spins. Combining such devices with dispersive microwave readout circuitry allows the spin sensitivity to be further improved by overcoming the standard thermal limit. Here we report on the fabrication and dispersive microwave readout of an array of niobium nanobridge rf SQUIDs incorporated into a superconducting resonator, including the optimization of the nanobridge fabrication process by electron beam lithography. We show the measured flux-tuneability of the resonance is in good agreement with theory, and we also discuss how the nonlinearity of the weak-link in the resonator structure allows for the mediation of parametric effects to enhance performance.

Tungsten is proposed as a tokamak divertor armour due to its good erosion resistance. Combining tungsten coatings with copper as a base material can overcome problems with machinability, lower the weight and reduce the component cost. The erosion rate must be known to estimate the lifetime of plasma facing components.This work aims to compare selected tungsten coatings to check if the erosion rate remains as good. It also compares the experimental data to a developed code based on previous work that aims to be quick and simple while giving reasonable results. In this study a set of erosion experiments were undertaken to measure the sputter yield in different conditions at partner organisations; Helium ion beam erosion at Huddersfield University, Helium plasma erosion at the University of Liverpool, Argon plasma erosion at Plasma Quest Ltd and Xenon Focussed Ion Beam (FIB) erosion at University of Surrey This work compares sputter yields different tungsten samples: sheet material, Chemical Vapour Deposition tungsten coating, Additive Manufacture deposited tungsten and tungsten coatings laid down by Thermal Plasma Spray. These coatings are available commercially so are ready to deploy today. The experimental sputter yields were compared to theoretical predictions, based on previously published work. While the experimental results agreed well with the models in trend and angular dependence the quantitative agreement was only well predicted to within a factor of four.It was found that the coatings have similar, and sometimes slightly lower sputter yields, and therefore, on occasion, slightly better erosion performance than the stock tungsten sheet samples.

The reaction of C1 hydrocarbon fragments has been examined on α-Cr2O3(10 ī ī 2), α-Cr2O3(0001), α-Fe2O3(10 ī ī 2) and manganese oxides. The material choices allow some separation of structural and electronic effects, and an examination of the surface chemistry of oxides with 3d, 3d and 3d transition metal 3+ cations.

CO adsorption on the MnO(100) surface was studied using temperature programmed desorption (TPD) and density functional theory (DFT). TPD results show that CO is weakly-bound on MnO(100), with an experimental adsorption energy of -35.6 +/- 2.1 kJ/mol at terrace sites in the low coverage limit. PBE simulations suggest that CO adsorption causes an implausible (2 x 2) surface reconstruction. PBE+U simulations show no signs of surface reconstruction, and provide an accurate estimate of the adsorption energy (-36.4 kJ/mol) when combined with the DFT-D3 method with Becke-Jonson damping to correct for van der Waals interactions. This simulation also shows that CO adsorbs C-down onto the Mn2+ terrace site in a tilted geometry, which is also observed experimentally and computationally on the similarly-structured NiO(100) transition metal oxide surface. TPD results for large doses show a plateauing of the coverage at about 0.4 monolayers of CO at 85 K, with a defect coverage equivalent to 0.08 monolayers. Adsorption associated with defect sites is indicated by a high-temperature desorption tail which is not satisfactorily explained by DFT simulations of simple step or oxygen vacancy defects.

O2 adsorption on MnO(100) precovered with sodium (Na) multilayers was investigated by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Deposition of Na multilayers leads to a first monolayer of oxidic Na followed by metallic Na island growth. XPS results for the oxidation of the metallic Na islands indicate an incomplete oxidation of Na at 125 K. Oxidation at 350 K completely oxidizes the metallic islands producing a mixture of Na2O and Na2O2. Thermal evolution of the oxidation products was examined. After oxidation at 350 K and flashing to 750 K, Na2O and Na2O2 are the primary oxides on MnO(100). After flashing to 850 K, a solid state reaction of Na2O2/Na2O and the MnO(100) substrate forms a NaMnO2-like surface compound which decomposes above 850 K. Oxygen exchange between CO2 and Na oxides is observed. The strong interaction between CO2 and Na oxide islands forms Na2CO3 on MnO(100). Heating the Na2CO3 covered MnO(100) surface to 600 K for 10 min drives oxidic Na in the first monolayer into the MnO subsurface, and produces a surface exposing islands of Na2CO3 on MnO(100).

The theoretical error rates in deterministic ion implantation when using an ion beam governed by a Poisson point process with a detector that counts the impacts are investigated. It is concluded that if the error rates are small, then for spots with nominally one implanted ion the probability of failure to implant the correct number is ≈ for a synchronous (i.e., pulsed) system or for an asynchronous (i.e., continuous beam) system, where is the probability that the detector misses an ion impact, and and are the number of ions (dark counts) per unit time and per pulse, respectively. t s is the system reaction time for an asynchronous system. This approximation allows easy identification of the greatest need for engineering effort. Some experimental efforts to measure these parameters and their uncertainties are examined.

SQUIDs (Superconducting Quantum Interference Devices) are macroscopic quantum devices capable of detecting and measuring a wide variety of physical parameters with unprecedented sensitivity. SQUIDs based on nanobridge weak links have shown increasing promise for quantum information and quantum sensing applications such as single spin detection. Focussed ion beam etched nanobridges have properties which can enhance nanoSQUID device performance but are often limited in terms of their non-hysteretic operating temperature range. Here we describe measurements of FIB-milled nanobridges, as single weak links or in nanoSQUIDs, made using either Ga, Xe or Ne ion beam sources. Their properties as a function of temperature, bias current, magnetic field and microwave power are measured and modelled according to a range of superconductivity models, as a means for improved understanding of the associated nanobridge parameters. We further propose techniques to extend the non-hysteretic operating temperature range of the devices.

Herein, the results from a focused ion beam instrument, designed to implant single ions with a view to the fabrication of qubits for quantum technologies, are presented. The difficulty of single ion implantation is accurately counting the ion impacts. This is achieved here through the detection of secondary electrons generated upon each ion impact. The implantation of single bismuth ions with different charge states into Si, Ge, Cu, and Au substrates is reported, and the counting detection efficiency for single ion implants and the factors that affect such detection efficiencies are determined. It is found that for 50 keV implants of Bi++ ions into silicon an 89% detection efficiency can be achieved, which is the first quantitative detection efficiency measurement for single ion implants into silicon without implanting through a thick SiO2 film. This level of counting accuracy provides implantation of single impurity ions with a success rate significantly exceeding that achievable by random (Poissonian) implantation.

Abstract The structures of the silica polymorphs α-quartz and stishovite have been geometry optimized at highly simulated isotropic pressure within the framework of Density Functional Theory. The atoms of the high-pressure polymorph stishovite are virtually incompressible with the bonded radii for Si and O atoms decreasing by only 0.04 and 0.08 Å, respectively, at 100 GPa. In compensating for the increase in the effective interatomic potential associated with the compression of the Si-O bonded interactions, the electron density at the bond critical point between the bonded pair increases from 0.69 to 0.89 e/ Å3. The bonded radii of the Si and O atoms for α-quartz decrease by 0.006 and 0.008 Å, respectively, between 1 bar and 26.4 GPa. The impact of simulated, isotropic pressure on the bonded radii of the atoms for three perovskites YAlO3, LaAlO3, and CaSnO3 was also examined at high pressure. For the YAlO3 perovskite, the bonded radii for Y and Al decrease by 0.06 and 0.05 Å, respectively, at 80 GPa, while the electron density between the bonded atoms increases by 0.12 and 0.15 e/Å3, on average. The calculations also show that the coordination number of the Y atom increases from 9 to 10 while the coordination number of the O1 atom increases concomitantly in the structure from 5 to 6 at 20 GPa. Hence pressure not only promotes an increase in the coordination number of the metal atoms but also a necessary concomitant increase in the coordination number of the O atoms. The bonded radii, determined at a lower pressure between 0.0 and 15 GPa for LaAlO3 and CaSnO3, decrease a smaller amount with the radii for the La and Ca atoms decreasing by 0.03 and 0.04 Å, respectively, while the radii for the smaller Al and Sn atoms decrease by 0.01 and 0.02 Å, respectively. In general, O atoms are more compressible than the metal atoms, but overall the calculations demonstrate that the bonded radii for the atoms in crystals are virtually incompressible when subjected to high pressure. The reason that the bonded radii change little when subjected to high pressure is ascribed to the changes in the effective interatomic potentials that result in increased repulsion when the atoms are squeezed together.

Niobium-based nanobridge superconducting quantum interference devices (SQUIDs) have shown very low noise performance and high-frequency operation. We describe how we are bringing together these two aspects of nanobridge SQUIDs with the aim of realizing single spin-flip detection using microwave inductive readout techniques, where the nanobridge SQUID is integrated into a superconducting coplanar waveguide resonator. Using electron beam lithography (EBL) is ideal for fabricating nanobridge junctions and has the advantage of being easily scalable compared to using a focused ion beam. In this article, we demonstrate that EBL is suitable for fabricating nanobridge junction SQUIDs, and they exhibit very comparable performance to previous focused ion beam milled SQUIDs. Our integrated devices show potential to be used for flux-tunable sensors.

The microwave properties of nano-scale structures are important in a wide variety of applications in quantum technology. Here we describe a low-power cryogenic near-field scanning microwave microscope (NSMM) which maintains nano-scale dielectric contrast down to the single microwave photon regime, up to $10^{9}$ times lower power than in typical NSMMs. We discuss the remaining challenges towards developing nano-scale NSMM for quantum coherent interaction with two-level systems as an enabling tool for the development of quantum technologies in the microwave regime.

Quantum computers have been proposed that exploit entangled quantum states between atoms that are isolated from environmental perturbations in a "semiconductor vacuum" which can be formed by cryogenically cooling an isotopically pure, defect free crystalline layer consisting of Si, or Ge. In a preliminary investigation of an implant and deposition layer exchange technique to produce such "vacuums", a layer of aluminium was implanted with Si-28 using a conventional implanter. After annealing and cross sectioning, layer exchange was observed to have produced multiple isolated crystals in a cross sectional TEM image. Further deposited Al layers were implanted with Ge using a SIMPLE (Single Ion Multispecies Positioning at Low Energy) implanter over a range of fluences. After anneals at 250 degrees C and Al removal, crystals of Ge (which also contained Si) were seen at areal densities that increased with implant fluence.

Magnetic nanostructures, as part of hybrid CMOS technology, have the potential to overcome silicon's scaling limit. However, a major problem is how to characterize their magnetization without disturbing it. Magnetic force microscopy (MFM) offers a convenient way of studying magnetization, but spatial resolution and sensitivity are usually boosted at the cost of increasing probe-sample interaction. By using a single magnetic domain wall (DW), confined in a V-shape nanostructure fabricated at the probe apex, it is demonstrated here that the spatial resolution and the magnetic sensitivity can be decoupled and both enhanced. Indeed, owing to the nanostructure's strong shape anisotropy, DW-probes have 2 high and 2 low magnetic moment states with opposite polarities, characterised by a geometrically constrained pinned DW, and curled magnetization, respectively. Electron holography studies, supported by numerical simulations, and in situ MFM show that the DW-probe state can be controlled, and thus used as a switchable tool with a low/high stray field intensity.

An important requirement across a range of sensitive detectors is to determine accurately the energy deposited by the impact of a particle in a small volume. The particle may be anything from a visible photon through to an X-ray or massive charged particle. We have been developing nanobridge Josephson junctions based SQUIDs and nanoSQUID devices covering the entire range of particle detection energies from leV to MeV. In this paper we discuss some developments in nanobridge Josephson junctions fabrication using focussed ion beam (FIB) and how these developments impact future applications. We focus on tuning of the transition temperature of a superconducting thin-film absorber, with the aim to match the absorber T-c to the working temperature range of the SQUID and also on using a new Xe FIB to improve Josephson junction and superconducting film quality.

The oxidation of clean and Na precovered MnO(100) has been investigated by X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and temperature programmed desorption (TPD) of adsorbed water. XPS results indicate that Mn3O4-like and Mn2O3-like surfaces can be formed by various oxidation treatments of clean and nearly-stoichiometric MnO(100), while a NaMnO2-like surface can be produced by the oxidation of MnO(100) pre-covered with multilayers of metallic Na. Water TPD results indicate that water adsorption/desorption is sensitive to the available oxidation states of surface Mn cations, and can be used to distinguish between surfaces exposing Mn2+ and Mn3+ cations, or a combination of these oxidation states. Carbon dioxide and water TPD results from the NaMnO2-like surface indicate that pre-adsorbed water blocks the uptake of CO2, while water displaces pre-adsorbed CO2. No indication of a strong reactive interaction is observed between CO2, water and the NaMnO2-like surface under the conditions of our study.

2D and 3D measurements of two WC-Co hardmetal alloys have been made using electron backscatter diffraction and focused ion beam microscopy. The 3D network of the Cobalt binder phase has been shown to be comprised of both small isolated Co grains as well as the large interpenetrating grains previously surmised to exist from 2D mapping; grain boundaries between the large Co grains have also been observed for the first time in 3D. 2D and 3D WC grain size distributions are shown to correspond closely, but only if the measurements of small grains are discounted as few grains below about 40% of the mean size are seen in 3D, even though much smaller sections are seen in 2D views. Analysis of grain shape has found the presence of truncated trigonal prisms with faces having the expected basal and prism plane orientations, but it also reveals complex shapes produced by multiple adjacent grains of almost identical orientation.

Nano-SQUIDs which can be the readout for inductive superconducting transition edge detectors (ISTED) were fabricated on monolayer niobium (Nb) film by focus ion beam (FIB) milling. The dimension of the nanobridges which formed the junctions was less than 60 nm and the diameter of the loop was 20 μm, The properties of this nano-SQUID were investigated. The design of ISTED was introduced and the transition temperature (T c ) of the absorbing layer was adjusted by both the thickness and the proportion Si doping of Nb.