199 results found
Delle LE, Pachauri V, Sharma S, et al., 2018, ScFv-modified graphene-coated IDE-arrays for 'label-free' screening of cardiovascular disease biomarkers in physiological saline, BIOSENSORS & BIOELECTRONICS, Vol: 102, Pages: 574-581, ISSN: 0956-5663
Hanham S, Watts C, Ahmad M, et al., Photonic crystal resonators for terahertz sensing applications, Progress in Electromagnetics Research Symposium, Publisher: IEICE, Pages: 803-803
Ma Z, Hanham SM, Huidobro PA, et al., 2017, Terahertz particle-in-liquid sensing with spoof surface plasmon polariton waveguides, APL Photonics, Vol: 2, ISSN: 2378-0967
We present a highly sensitive microfluidic sensing technique for the terahertz (THz) region of the electromagnetic spectrum based on spoof surface plasmon polaritons (SPPs). By integrating a microfluidic channel in a spoof SPP waveguide, we take advantage of these highly confined electromagnetic modes to create a platform for dielectric sensing of liquids. Our design consists of a domino waveguide, that is, a series of periodically arranged rectangular metal blocks on top of a metal surface that supports the propagation of spoof SPPs. Through numerical simulations, we demonstrate that the transmission of spoof SPPs along the waveguide is extremely sensitive to the refractive index of a liquid flowing through a microfluidic channel crossing the waveguide to give an interaction volume on the nanoliter scale. Furthermore, by taking advantage of the insensitivity of the domino waveguide’s fundamental spoof SPP mode to the lateral width of the metal blocks, we design a tapered waveguide able to achieve further confinement of the electromagnetic field. Using this approach, we demonstrate the highly sensitive detection of individual subwavelength micro-particles flowing in the liquid. These results are promising for the creation of spoof SPP based THz lab-on-a-chip microfluidic devices that are suitable for the analysis of biological liquids such as proteins and circulating tumour cells in buffer solution.
Adabi M, Lischner J, Hanham SM, et al., 2017, Microwave study of field-effect devices based on graphene/aluminum nitride/graphene structures, Scientific Reports, Vol: 7, ISSN: 2045-2322
Metallic gate electrodes are often employed to controltheconductivity of graphene based field effect devices. The lack of transparency of such electrodes in many optical applicationsis akeylimiting factor.We demonstrate a working concept of a doublelayer graphene field effect device that utilizesa thin film of sputtered aluminum nitride asdielectric gate material. For this system, we show that the graphene resistance can be modified by a voltage between the twographene layers.We studyhow a second gate voltage applied to the silicon back gatemodifies the measured microwave transport data ataround 8.7GHz. As confirmed bynumerical simulations based on the Boltzmann equation, this system resembles a parallel circuit of two graphene layers with different intrinsic doping levels. The obtained experimental results indicate that the graphene-aluminum nitride-graphenedevice concept presents a promising technology platform for terahertz-to-optical devices as well asradio-frequency acoustic deviceswhere piezoelectricity in aluminumnitride can also be exploited.
Hanham SM, Ahmad MM, Lucyszyn S, et al., 2017, LED-switchable High-Q Packaged THz Microbeam Resonators, IEEE Transactions on Terahertz Science and Technology, Vol: 7, Pages: 199-208, ISSN: 2156-342X
This paper describes the design, fabrication and experimental characterization of photonic crystal microbeam cavity resonators for the terahertz band implemented using suspended dielectric rectangular waveguide (DRW) in high resistivity silicon. Electrical quality factors of up to 11,900, combined with small modal volumes of 0.28 mm3 and 0.077 mm3, are demonstrated for devices operating at 100 and 200 GHz, respectively. The devices are found to be extremely light-sensitive, opening up new opportunities for light-controlled switching devices at terahertz frequencies. It is shown that the quality factor of the resonator can be tuned and the resonance extinguished through photo-illumination with an infrared light-emitting diode (IR LED). Additionally, the questions of thermal tunability and thermal stability of the resonators are examined. The demonstrated resonators are inherently suited to integration with DRW and by silicon bulk micromachining represent an attractive approach for realizing microphotonic integrated circuits for terahertz systems-on-a-substrate.
Watts C, Hanham SM, Ahmad MM, et al., 2017, Coupled Dielectric-Split Ring Microwave Resonatorfor Liquid Measurements in Microfluidic Channels atNanoliter Volumes, European Microwave Conference, Publisher: IEEE
A microwave dielectric resonator based sensor system has been investigated with respect to its sensitivity for the assessment of aqueous liquids. The system exploits the field enhancement of a split ring structure while retaining high and tunable quality factors due to weak and adjustable coupling between a planar split-ring and a dielectric resonator. The proposed sensor with integrated microfluidic channel allows investigation of volumes of liquids less than 1 nL and is capable of detecting small changes in relative permittivity, as demonstrated by measurements of water-ethanol solutions.
Klein N, Watts C, Hanham SM, et al., 2016, Microwave-to-terahertz dielectric resonators for liquid sensing in microfluidic systems, Conference on Terahertz Emitters, Receivers, and Applications VII, Publisher: Society of Photo-optical Instrumentation Engineer, ISSN: 0277-786X
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.
The transfer process of graphene onto the surface of oxide substrates is well known.However, for many devices, we require high quality oxide thin films on the surface ofgraphene. This step is not understood. It is not clear why the oxide should adopt theepitaxy of the underlying oxide layer when it is deposited on graphene where there isno lattice match. To date there has been no explanation or suggestion of mechanismswhich clarify this step. Here we show a mechanism, supported by first principlessimulation and structural characterisation results, for the growth of oxide thin films ongraphene. We describe the growth of epitaxial SrTiO3 (STO) thin films on a grapheneand show that local defects in the graphene layer (e.g. grain boundaries) act as bridgepillarspots that enable the epitaxial growth of STO thin films on the surface of thegraphene layer. This study, and in particular the suggestion of a mechanism forepitaxial growth of oxides on graphene, offers new directions to exploit thedevelopment of oxide/graphene multilayer structures and devices.
Wang R, Pearce R, Gallop J, et al., 2016, Investigation of CVD graphene topography and surface electrical properties, SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES, Vol: 4, ISSN: 2051-672X
Hanham SM, Watts C, Otter WJ, et al., Probing the THz response of biological cells using photonic crystal resonators, Energy Materials Nanotechnology (EMN) Meeting on Terahertz
Goniszewski S, Adabi M, Shaforost O, et al., 2016, Correlation of p-doping in CVD Graphene with Substrate Surface Charges, Scientific Reports, Vol: 6, ISSN: 2045-2322
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 (SiO2) substrates prior to CVD graphene transfer are measured. Beginning with graphene on untreated thermal oxidised silicon, a minimum conductivity (σmin) occurring at gate voltage Vg = 15 V (Dirac Point) is measured. It was found that more aggressive treatments (O2 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 Vg at σmin 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.
Otter W, Hu F, Hanham S, et al., Terahertz metamaterial devices, International Conference on Semiconductor Mid-IR and THz Materials and Optics (SMMO2016)
Gregory AP, Blackburn JF, Lees K, et al., 2016, Measurement of the permittivity and loss of high-loss a Near-Field Scanning Microwave Microscope, ULTRAMICROSCOPY, Vol: 161, Pages: 137-145, ISSN: 0304-3991
Gajewski K, Goniszewski S, Szumska A, et al., 2016, Raman Spectroscopy and Kelvin Probe Force Microscopy characteristics of the CVD suspended graphene, Diamond and Related Materials, Vol: 64, Pages: 27-33, ISSN: 0925-9635
In this work we present combined Kelvin probe force microscopy and Raman spectroscopy studies of supported and suspended structures formed out of chemical vapor deposition (CVD) grown graphene. Work function of both suspended and supported graphene was -4.81 ± 0.06eV and -4.92 ± 0.06eV respectively. By G and 2D modes correlation we showed, that CVD graphene was influenced by biaxial strain. Increased contact potential difference (CPD) on the suspended graphene in comparison with the areas of the supported graphene was the sign of increased strain (from 0.05% to ~ 0.12%) rather than decreased doping (p-doping decreased from ~ 5.5 × 1012cm-2 to ~ 4.5 × 1012cm-2).
Otter WJ, Hanham SM, Klein N, et al., 2016, Millimeter-wave negative group delay network, URSI Asia-Pacific Radio Science Conference (URSI AP-RASC), Publisher: IEEE, Pages: 1205-1207
Goniszewski S, Gallop J, Adabi M, et al., 2015, Self-supporting graphene films and their applications, IET CIRCUITS DEVICES & SYSTEMS, Vol: 9, Pages: 420-427, ISSN: 1751-858X
Hanham S, Watts C, Otter WJ, et al., 2015, Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies, Applied Physics Letters, Vol: 107, ISSN: 1077-3118
Dadshani S, Kurakin A, Amanov S, et al., 2015, Non-invasive assessment of leaf water status using a dual-mode microwave resonator, PLANT METHODS, Vol: 11, ISSN: 1746-4811
Shaforost O, Wang K, Goniszewski S, et al., 2015, Contact-free sheet resistance determination of large area graphene layers by an open dielectric loaded microwave cavity, JOURNAL OF APPLIED PHYSICS, Vol: 117, ISSN: 0021-8979
Ng B, Hanham SM, Wu J, et al., 2014, Broadband Terahertz Sensing on Spoof Plasmon Surfaces, ACS PHOTONICS, Vol: 1, Pages: 1059-1067, ISSN: 2330-4022
Otter WJ, Hanham SM, Ridler NM, et al., 2014, 100 GHz ultra-high Q-factor photonic crystal resonators, SENSORS AND ACTUATORS A-PHYSICAL, Vol: 217, Pages: 151-159, ISSN: 0924-4247
Basey-Fisher TH, Guerra N, Triulzi C, et al., 2014, Microwaving Blood as a Non-Destructive Technique for Haemoglobin Measurements on Microlitre Samples, ADVANCED HEALTHCARE MATERIALS, Vol: 3, Pages: 536-542, ISSN: 2192-2640
Basey-Fisher TH, Guerra N, Triulzi C, et al., 2014, Blood measurements: microwaving blood as a non-destructive technique for haemoglobin measurements on microlitre samples (adv. Healthcare mater. 4/2014)., Adv Healthc Mater, Vol: 3
The electric field component of the microwaves emanating from the dielectric resonator is able to penetrate the microfluidic channel, serum, and individual blood cells. Subsequently, it interacts with every hemoglobin molecule present within each red blood cell. On page 536 , Toby H. Basey-Fisher and team conclude that the dielectric contrast between water and hemoglobin means that a change in the hemoglobin concentration leads to a change in the microwave response.
Gregory A, Hao L, Klein N, et al., 2014, Spatially resolved electrical characterisation of graphene layers by an evanescent field microwave microscope, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, Vol: 56, Pages: 431-434, ISSN: 1386-9477
Gregory AP, Blackburn JF, Lees K, et al., 2014, A Near-Field Scanning Microwave Microscope for measurement of the permittivity and loss of high-loss materials, ARFTG Microwave Measurement Conference, Publisher: IEEE
Klein N, Hanham SM, Basey-Fisher TH, et al., 2014, Micro- and millimetre wave measurements of nanolitre biological liquids by dielectric resonators, IEEE MTT-S International Microwave Workshop Series on: RF and Wireless Technologies for Biomedical and Healthcare Applications (IMWS-Bio 2014), Publisher: IEEE
Otter WJ, Hanham SM, Klein N, et al., 2014, W-band Laser-controlled Photonic Crystal Variable Attenuator, IEEE MTT-S International Microwave Symposium (IMS), Publisher: IEEE, ISSN: 0149-645X
Goniszewski S, Shaforost O, Klein N, et al., 2014, Frequency Readout of Nanomechanical Graphene Drums via a Microwave Resonator Coupling Method, 44th European Microwave Conference (EuMC), Publisher: IEEE, Pages: 363-366, ISSN: 2325-0305
Hanham SM, Navarro-Cia M, Ng B, et al., 2014, Exploiting plasmonics for THz and infrared sensing, Conference on Terahertz Physics, Devices, and Systems VIII - Advanced Applications in Industry and Defense, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Bio-sensing by electromagnetic waves from GHz towards THz frequencies, although not yet established as a common method for biomedical applications, offers challenging opportunities, which are complementary to the established optical methods, often based on plasmonic waves and resonances. The longer wavelength - in comparison to visible and IR provides a disadvantage in terms of the smallest possible interaction volume, which can be partially overcome by evanescent field methods. However, the high absorption of micro- and millimetre waves by liquid water, which is the most abundant component of biological substances, provides a unique observation window, which is substantially different and therefore complementary to the other parts of the electromagnetic spectrum. © 2013 IEEE.
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