51 research outputs found
Embroidered rectangular split-ring resonators for material characterisation
No full textIn this paper, we report an embroidered rectangular split-ring resonator (SRR) operating at S band for sensing applications. We designed, fabricated and characterized the SRR sensor on a fabric that can conformally cover the surface of samples under investigation. The structure can be embroidered on any dielectric fabric at low cost using conventional embroidery methods. In addition, the method is suitable for the fabrication of large-scale arrays to cover large surfaces. We have demonstrated material characterization capability of the sensors using a specific design with a length of 60 mm and a width of 30 mm. We wrapped the sensors on low-density polyethylene (LDPE) bottles filled with deionized (DI) water and ethanol in our experiments and measured their resonant frequencies using a vector network analyzer (VNA). We measured the nominal resonant frequency of a specific sensor wrapped around an empty bottle as 2.06 GHz with a quality factor of 411. The shifts in resonant frequencies when the bottle was filled with ethanol and DI water are 42 MHz and 66 MHz, respectively
Embroidered Rectangular Split-Ring Resonators for the Characterization of Dielectric Materials
No full textIn this paper, we report an embroidered rectangular split-ring resonator (SRR) operating at S band for material characterization based on the differences in dielectric parameters. We designed, fabricated and characterized SRR sensors on a conventional fabric that can be conformally attached over the surface of samples under investigation. The structures are made of conductive threads and can be embroidered on any dielectric fabric at low cost using conventional embroidery methods. We have demonstrated material characterization capability of the sensors using a specific design with a length of 60 mm and a width of 30 mm. We wrapped the sensors on low-density polyethylene (LDPE) bottles filled with deionized (DI) water and common solvents (ethanol, methanol, isopropanol and acetone) in our experiments. We measured the nominal resonant frequency of a specific sensor wrapped around an empty bottle as 2.07 GHz. The shifts in resonant frequencies when the bottle was filled with the solvents follow the dielectric constants of the solvents
An embroidered slot-loaded patch antenna for characterization of dielectric materials
No full textEmbroidery has been recently introduced as a new method to realize sensors especially for wearables. In this paper, we present a slot-loaded embroidered patch antenna to provide a simplified setup which allows the antenna to act as a stand-alone resonator. The design procedure, simulation and implementation of an embroidered sensor are presented and discussed. It is demonstrated that this structure can be used without any need for external antennas as a wireless sensor. To demonstrate the feasibility of this technique, the design process using a slot-loaded antenna to achieve a high Q antenna, fabricated on an FR4 substrate, is presented and discussed. This structure is then manufactured, with practical results shown to agree with simulated results. Using this as a basis for subsequent designs, an embroidered slot-loaded patch is presented and discussed. We demonstrate this capability in an experiment where a set of solvents inside plastic bottles were interrogated using the embroidered antennas
Fabrication Optimisation of Metal-Oxide-Metal Diodes
No full textThis thesis is based on the design, research and development of devices required to successfully recover waste heat and convert it into electrical power through the use of Microsystems Technology. This takes place using optical nano-antennas, in the same way a radio antenna picks up a radio station. The main aim of this project is the rectification of this signal into a useful DC voltage. Here we have used high frequency metal-oxide-metal (MOM) diodes, which involve the use of two dissimilar metals separated by a native oxide.
In order to make successful MOM diodes, the following must be considered: maximise the work function difference between the metals for asymmetry in I-V characteristics, produce a uniform oxide layer that is sufficiently thin (a few nm) for electron tunnelling to occur and reduce the diode size to sub-micron dimensions to increase the cut-off frequency. Currently the diodes consist of titanium, titanium oxide and platinum, which provides a high enough work function difference that the I-V characteristics show significant asymmetry and figure of merit values are among the best published. It has been found, using ToFSIMS and TEM analysis of the oxide, that the thickness of the oxide can be controlled between 1 nm and 7 nm using RIE etching and subsequent oxygen plasma regrowth. Different oxides have been fabricated with different stoichiometries depending on the process used. Furnace oxidation grows a complex oxide in the range 6.9 to 7.6 nm thick. By contrast a more simple oxide can be produced using a controlled reactive ion etch and subsequent plasma oxidation, with thicknesses in the range 1 to 6 nm.
The final significant issue involves the cross-sectional area of the diodes, which also determines their cut-off frequency. Extrapolation of existing diode results suggests that, if made sufficiently small, they would function at high enough frequencies for rectification of radiation in the terahertz regime. Furthermore, phase shift lithography has been used to demonstrate 200 to 400nm lines in diode features, with alternative possible high scale processes discussed for future fabrication
Metal-insulator-metal diodes fabricated on flexible substrates
No full textThe fabrication and testing of metal-insulator-metal (MIM) diodes on a flexible substrate for microwave and mm-wave applications are presented. The diodes utilized octadecyltrichlorosilane (OTS), which self assembles to form a thin, pin holes free insulator. Preliminary electrical analysis shows that the diodes have a typical zero bias resistance of approximately 80 kΩ, zero-bias curvature coefficient (γ_ZB) of approximately 5.5 V-1, and voltage responsivity of 3.1 kV/W at a frequency of 1 GHz, and are produced with over 90% device yield. The fabrication process is simple and cost effective, environmentally friendly, and demonstrates the possibility of roll-to-roll volume manufacturing of MIM diodes
Enhanced narrow-band operation of ultra-fast rectennas
No full textAn effective impedance matching technique for rectennas (an antenna coupled with rectifier) operating at specific frequencies is presented. The rectifier consists of a MIM junction with a molecular insulator. The method used two coplanar strip lines emerging from the antenna feed-point, to correct for the reactive component of the antenna impedance on one side, and to connect the rectifier and transform its impedance on the other side. Microwave and mm-wave characterization of the devices showed that the output voltage of the impedance matched rectenna is almost an order of magnitude higher than that of a control device without matching network at 20 GHz
Conduction mechanisms in metal/self-assembled monolayer/metal junction
No full textThe conduction mechanisms in metal-insulator-metal (MIM) junctions where the insulator consists of a self-assembled monolayer are investigated. Temperature dependence measurements from 2.5 to 300 K, show that the conduction is dominated by tunnelling only for temperatures below 20 K, while at higher temperatures surface-limited and bulk-limited mechanisms are observed. The experimental results are explained using a combination of direct (Simmons) tunnelling, Schottky emission, and Poole-Frenkel theory. Further insight is gained through numerical simulations based on the non-equilibrium Green-function formalism
Ti-TiOx-Pt Metal-Oxide-Metal Diodes Fabricated via a Simple Oxidation Technique
No full textThis work presents the successful production, via a simple oxidation process, of Ti-TiOx-Pt Metal-Oxide-Metal diodes with excellent electrical asymmetry. TEM analysis has been used to verify the oxide thickness. A thicker layer produces better diodes, although they are of a less uniform nature. The conduction mechanism in these diodes is still under investigation
High-Performance Atomic Layer Deposited Al2O3 Insulator Based Metal-Insulator-Metal Diode
No full textThe fabrication of metal–insulator– metal (MIM) diode using an ultrathin Al2O3 insulator layer, deposited using atomic layer deposition (ALD) is presented. The Al2O3 insulating layer was found to be highly uniform throughout the diode junction, effectively overcoming the main fabrication challenge in MIM diodes. The diodes exhibit strong non-linear current–voltage curves, have a typical zero-bias curvature coefficient of 5.4 V−1 and a zero-bias resistance of approximately 118 kΩ, a value considerably smaller than other MIM diode topologies and that allows more current to be rectified. Other results including current ratio and yield of the diode also competes favorably with the state-of-the-art MIM diodes such as the recently produced metal-octadecyltrichlorosilane (OTS)-metal structure
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