Carl J. Anthony

Quality and reliability of wet and dry oxides on n-type 4H-SiC

Abstract The thermal oxide on silicon carbide (SiC) is found to be subtly different from that grown on silicon and many basic oxide characterisation experiments still remain to be carried out. Here a comparison is made between the breakdown properties and wet and dry thermally grown oxides on n-type 4H-SiC over the temperature range 25–300°C. The interface characteristics are also compared for the two oxides. It was found that for temperatures up to 200°C the dry oxide could have more than an order of magnitude larger charge to breakdown than that found for the wet oxide, whilst having no significant difference in interface state density or fixed oxide charge. At 300° the breakdown mechanism changed and became process independent.

Printable ink holograms

The development of single-step printable holographic recording techniques can enable applications in rapid data storage, imaging, and bio-sensing. The personalized use of holography is limited due to specialist level of knowledge, time consuming recording techniques, and high-cost equipment. Here, we report a rapid and feasible in-line reflection recording strategy for printing surface holograms consisting of ink using a single pulse of a laser light within seconds. The laser interference pattern and periodicity of surface grating as a function of tilt angle are predicted by computationally and demonstrated experimentally to create 2D linear gratings and three-dimensional (3D) images. We further demonstrate the utility of our approach in creating personalized handwritten signatures and 3D images.

Characterization of coupled micro/nanoresonators using inverse eigenvalue analysis

This paper reports a method of determining the system matrix of a nearest neighbor coupled array of micro/nanomechanical resonators. The simple method requires contacts to only one element of the array to determine two sets of eigenvalues related to the system matrix. The elements of the system matrix are then determined from these eigenvalues. This system matrix can then be used to determine the characteristics of the individual resonators or as the starting point for a perturbation analysis to determine the changes observed when a functionalized array of resonators is used as a sensor.

Interface State Capture Cross Section Measurements on Vacuum Annealed and Radiation Damaged Si : SiO2 Surfaces

The conductance technique can be used to separate two types of fast interface state differentiated by a factor of about 20 ratio in capture cross section. By comparing vacuum annealed oxides, which are dominated by P b defects, with radiation damaged oxides, we infer that the two types are acceptor and donor states. The conductance measurements are unable to separate P bo and P hi on the (100) surface. In vacuum annealed samples, the conductance peak broadening is dominated by surface potential fluctuations, whereas radiation damaged samples have an intrinsically broadened cross section over and above that due to the potential fluctuations.

Design and Development of a Nonintrusive Pressure Measurement System for Pipeline Monitoring

In recent years, wireless sensor network systems have increasingly been used to monitor infrastructure health. Advances in electronics and sensing systems have enabled the development of various pressure-sensing methods for pipe-pressure monitoring. This article presents laboratory-based test results as part of the development and validation of a pipeline pressure-monitoring method based on force sensitive resistors (FSR). Additionally, to validate the data, the proposed pressure-sensing method is compared with a commercially available direct-pressure sensor. Analysis of the data shows a significant correlation (correlation factor = 0.9928) between the commercial sensor and the proposed sensor. These results showed that the proposed method has an acceptable accuracy and reliability even though it is not ultimately intended for absolute-pressure measurements, but for monitoring relative pressure changes in pipes.

High-performance ferroelectric and magnetoresistive materials for next-generation thermal detector arrays

This paper discusses the potential thermal imaging performance achievable from thermal detector arrays and concludes that the current generation of thin-film ferroelectric and resistance bolometer based detector arrays are limited by the detector materials used. It is proposed that the next generation of large uncooled focal plane arrays will need to look towards higher performance detector materials - particularly if they aim to approach the fundamental performance limits and compete with cooled photon detector arrays. Two examples of bolometer thin-film materials are described that achieve high performance from operating around phase transitions. The material Lead Scandium Tantalate (PST) has a paraelectric-to-ferroelectric phase transition around room temperature and is used with an applied field in the dielectric bolometer mode for thermal imaging. PST films grown by sputtering and liquid-source CVD have shown merit figures for thermal imaging a factor of 2 to 3 times higher than PZT-based pyroelectric thin films. The material Lanthanum Calcium Manganite (LCMO) has a paramagnetic to ferromagnetic phase transition around -20oC. This paper describes recent measurements of TCR and 1/f noise in pulsed laser-deposited LCMO films on Neodymium Gallate substrates. These results show that LCMO not only has high TCRs - up to 30%/K - but also low 1/f excess noise, with bolometer merit figures at least an order of magnitude higher than Vanadium Oxide, making it ideal for the next generation of microbolometer arrays. These high performance properties come at the expense of processing complexities and novel device designs will need to be introduced to realize the potential of these materials in the next generation of thermal detectors.

Effects of current on early stages of focused ion beam nano-machining

In this report we investigate the effects of focused ion beam machining at low doses in the range of 1015–1016 ions cm−2 for currents below 300 pA on Si(100) substrates. The effects of similar doses with currents in the range 10–300 pA were compared. The topography of resulting structures has been characterized using atomic force microscope, while crystallinity of the Si was assessed by means of Raman spectroscopy. These machining parameters allow a controllable preparation of structures either protruding from, or recessed into, the surface with nanometre precision.

Exploitation of multiple sensor arrays in electronic nose

The Coupled Micro Resonator Array (CMRA) is a new type chemical sensor that has been developed to improve the performance of the electronic nose by increasing the number of sensors that can be used to detect specific odours. In the CMRA, an array of mechanically coupled micro mass balances, the mass of each micro mass balance can be determined by measuring the eigenfrequencies of the coupled array, with just a single input and output electrode. If the mass of each resonator is to be uniquely identified it is important that the changes in the eigenfrequencies are distinctive and that the eigenvectors of the system are stable against resonator mass changes. This paper models and evaluates the performance of an unsymmetrical yet balanced CMRA for individual resonator mass determination.

Focused ion beam microfabrication in Foturan? photosensitive glass

The fabrication of nano-dimensional features in the photoetchable glass Foturan™ using focused ion beam technology has been characterized. To date, most microfabrication in this material has used UV lithography and UV lasers, with a minimum feature size of around 10 µm determined by the grain structure, though there has been some recent work using high energy proton irradiation. Focused ion beam technology offers two potential advantages: features are etched directly without post bake or HF wet etch and features can be generated with lateral and depth resolution on the nanoscale. Initial test features were milled to a depth of 1.46 µm, without distortion due to charging, at a milling rate of 0.23 µm3 nC−1, in agreement with our simulations.

High-fidelity replication of thermoplastic microneedles with open microfluidic channels

Development of microneedles for unskilled and painless collection of blood or drug delivery addresses the quality of healthcare through early intervention at point-of-care. Microneedles with submicron to millimeter features have been fabricated from materials such as metals, silicon, and polymers by subtractive machining or etching. However, to date, large-scale manufacture of hollow microneedles has been limited by the cost and complexity of microfabrication techniques. This paper reports a novel manufacturing method that may overcome the complexity of hollow microneedle fabrication. Prototype microneedles with open microfluidic channels are fabricated by laser stereolithography. Thermoplastic replicas are manufactured from these templates by soft-embossing with high fidelity at submicron resolution. The manufacturing advantages are (a) direct printing from computer-aided design (CAD) drawing without the constraints imposed by subtractive machining or etching processes, (b) high-fidelity replication of prototype geometries with multiple reuses of elastomeric molds, (c) shorter manufacturing time compared to three-dimensional stereolithography, and (d) integration of microneedles with open-channel microfluidics. Future work will address development of open-channel microfluidics for drug delivery, fluid sampling and analysis.