Correlation of p-doping in CVD Graphene with Substrate Surface Charges

Correlations between the level of p-doping exhibited in large area chemical vapour deposition (CVD) graphene field effect transistor structures (gFETs) and residual charges created by a variety of surface treatments to the silicon dioxide (SiO(2)) substrates prior to CVD graphene transfer are measured. Beginning with graphene on untreated thermal oxidised silicon, a minimum conductivity (σ(min)) occurring at gate voltage V(g) = 15 V (Dirac Point) is measured. It was found that more aggressive treatments (O(2) plasma and UV Ozone treatments) further increase the gate voltage of the Dirac point up to 65 V, corresponding to a significant increase of the level of p-doping displayed in the graphene. An electrowetting model describing the measured relationship between the contact angle (θ) of a water droplet applied to the treated substrate/graphene surface and an effective gate voltage from a surface charge density is proposed to describe biasing of V(g) at σ(min) and was found to fit the measurements with multiplication of a correction factor, allowing effective non-destructive approximation of substrate added charge carrier density using contact angle measurements

Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

Data supporting Hanham SM, Watts C, Otter WJ, LucyszynS and Klein N (2015) Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies. Applied Physics Letters, 107 (3), Article number: 032903Data supporting Hanham SM, Watts C, Otter WJ, LucyszynS and Klein N (2015) Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies. Applied Physics Letters, 107 (3), Article number: 03290

Microwave-to-terahertz dielectric resonators for liquid sensing in microfluidic systems

The microwave-to-terahertz frequency range offers unique opportunities for the sensing of liquids based on the degree of molecular orientational and electronic polarization, Debye relaxation due to intermolecular forces between (semi-)polar molecules and collective vibrational modes within complex molecules. Methods for the fast dielectric characterization of (sub-)nanolitre volumes of mostly aqueous liquids and biological cell suspensions are discussed, with emphasis on labon- chip approaches aimed towards single-cell detection and label-free flow cytometry at microwave-to-terahertz frequencies. Among the most promising approaches, photonic crystal defect cavities made from high-resistivity silicon are compared with metallic split-ring resonant systems and high quality factor (Q-factor) whispering gallery-type resonances in dielectric resonators. Applications range from accurate haemoglobin measurements on nanolitre samples to label-free detection of circulating tumor cells. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Temperature dependent hyperspectral terahertz imaging of human bone for disease diagnosis

Water is a fundamental component of many biological systems. The ability to detect water therefore provides great insight into system functionality, particularly in the development of disease. In this work, the high interaction of terahertz radiation with water, paired with the dependence of the dynamics of water molecules with varying temperature, is utilised to monitor changes in the composition of bone tissue. Heterotopic ossification (HO) bone samples and deionised free water are measured using terahertz time-domain spectroscopy for varying environmental temperatures, for prospective use in disease diagnosis

Silica Nanoparticle-based Photoresin for THz High-Resolution 3D Microfabrication by Two-Photon Polymerization

Two-photon polymerization is a promising fabrication technique for complex three-dimensional (3D) structures operating at TeraHertz (THz) given its sub-μm resolution with hundreds of mm3 print volume capability. However, standard photoresins exhibit unsuitably high THz absorption and have poor mechanical, chemical, and thermal stability. To address the latter three issues, a new photoresin (commercially known as GP-Silica) based on silica nanoparticles dispersed in a photocurable binder matrix has been recently developed. To assess its suitability for THz devices, we report the THz dielectric properties of GP-Silica and compare them with standard 3D printable materials. We find that GP-Silica outperforms the other photoresins by almost 5 times in terms of absorption, which finally unlocks additive manufacturing for THz applications

Broadband characterisation of interior materials and surface scattering using terahertz time-domain spectroscopy

Indoor wireless communications need to move towards Terahertz (THz) frequencies in order to keep up with society's demand for data transmission, but this change is currently hindered by limited knowledge of material properties and propagation and scattering models at these frequencies. The dielectric properties of common household materials are investigated here with a twofold objective: (1) to extend the library of material properties at THz, and (2) to estimate and disentangle losses in scattering measurements in order to facilitate propagation, scattering and, ultimately, channel models

Exploring the comprehensibility of ten different musical notation systems and underlying factors

Numerous systems of musical notation have been developed to address some of the complexities associated with conventional Staff notation, such as translating it into physical movements and memorizing the meaning of its symbols. Surprisingly, there has been little empirical research assessing and comparing the comprehensibility of conventional versus alternative notation methods. In this study, three main features were assessed for 10 different musical notation systems: discriminability (the ease of visually distinguishing pitch or duration changes in notation), iconicity (extent of resemblance between melodies and notation), and complexity. A total of 213 valid responses were collected in an online experiment. Participants completed two tasks, visual discriminability and melody-notation matching. They also provided complexity ratings for different notational systems. Multilevel Bayesian regression models show strong evidence that Figurenotes, Numbered notation, and Piano Roll notation have a relatively high level of discriminability, while Figurenotes, Proportional notation, Staff notation, and Piano Roll notation have a relatively high level of iconicity. Piano Roll notation was rated the least complex musical notation system. Differences in the results across pitch and duration dimensions, age, and musical sophistication were also found. Importantly, we also examined the effects of the different visual variables used by the notational systems (color, position, shape): changes in position have the highest discriminability, iconicity, and the lowest complexity. Qualitative analysis for some open questions also supported Piano Roll notation as being the most favorable musical notation, especially among novices

Hybrid reflection retrieval method for terahertz dielectric imaging of human bone

Terahertz imaging is becoming a biological imaging modality in its own right, alongside the more mature infrared and X-ray techniques. Nevertheless, extraction of hyperspectral, biometric information of samples is limited by experimental challenges. Terahertz time domain spectroscopy reflection measurements demand highly precise alignment and suffer from limitations of the sample thickness. In this work, a novel hybrid Kramers-Kronig and Fabry-Pérot based algorithm has been developed to overcome these challenges. While its application is demonstrated through dielectric retrieval of glass-backed human bone slices for prospective characterisation of metastatic defects or osteoporosis, the generality of the algorithm offers itself to wider application towards biological materials