1 

Critical consideration on the interpretation of impedance plots
The electrical response of dielectric materials is often graphically represented by means of a plot in the complex impedance (or admittance) plane. In many cases these impedance plots are semicircles. An equivalent circuit consisting of a capacitor (or a constant phase element) and two resistors is often used to describe such a semicircle. It is shown here that even if the experimental data are lying on such a semicircle they do not necessarily correspond to that equivalent circuit because of a different frequency dependency. In addition it is shown that the KramersKronig transforms can be very helpful but are not decisive for the determination of whether experimental errors are made.

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2 

Dispersion properties of an array of slots etched at the interface between two infinite dielectric materials
An array of long slots, oriented along x, etched on a ground plane that separates two infinite dielectric materials constitutes the basic canonical problem investigated in this article. In a single slot structure, the direction of radiation and the attenuation constant could be directly linked to the dominant leaky wave pole (kxlw) that dominates the pertinent Green’s Function (GF) spectrum in the longitudinal direction, x. In a multi slot problem, the number of poles that appear in the GF is equal to the number (N) of slots composing the array and in view of this two problems arise. First, how to locate efficiently these N poles in the kx spectrum of the GF parameters. Secondly to asses which of these poles are significant, i.e. dominate the behaviour of the array.

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3 

Bandwidth, Efficiency and Directivity Enhancement of Printed Antenna Performance Using Planar Circularly Symmetric EBGs
Planar Circularly Symmetric (PCS) Electromagnetic BandGap (EBG) substrates have been recently proposed to suppress the surface waves in printed technology [1] [2]. The major advantage of the PCSEBGs with respect to structures based on vertical pins [3] [4] is the fabrication simplicity since the dielectric slabs do not need to be perforated. With respect to other planar type of EBG [5], an advantage is that the surface waves launched by a central source are reduced equally in all radial directions. The motivation of this contribution is to design and measure a prototype which demonstrates the suppression of surface waves by a PCSEBG of a single antenna printed on a dielectric substrate. Thanks to the presence of the PCSEBG around the antenna, we obtain an enhancement of the bandwidth, efficiency and directivity performances. The study will present some design considerations for the PCSEBG itself, and then will proceed with the manufactured and measured antennas. The results explicitly show the advantages in terms of bandwidth and radiation pattern of the proposed EBG substrate. A bandwidth of 20% is achieved without significant surface wave losses.

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4 

Iterative solution of field problems with a varying physical parameter
In this paper, linear field problems with a varying physical parameter are solved with the conjugategradient FFT method and a dedicated extrapolation procedure for generating the initial estimate. The scheme is formulated and illustrated for two simple example problems. The importance of the choice of the stop criterion and the step size are demonstrated for the case of a straight thinwire segment. A brief summary is given of the applications that have appeared in the open literature until now, and actual threedimensional scattering problems for a rectangular conducting plate and an inhomogeneous, dispersive dielectric body are discussed. Finally, the case where the medium surrounding the object of interest is no longer homogeneous is addressed for two representative examples: wire antennas over a layered half space and an inhomogeneous dielectric cylinder in a waterfilled container

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5 

Highly stable carbon nanotube topgate transistors with tunable threshold voltage
Carbonnanotube topgate transistors with fluorinated dielectrics are presented. With PTrFE as the dielectric, the devices have absent or small hysteresis at different sweep rates and excellent biasstress stability under ambient conditions. Ambipolar singlewalled carbon nanotube (SWNT) transistors are observed when P(VDFTrFECTFE) is utilized as a topgate dielectric. Furthermore, continuous tuning of the threshold voltages of both unipolar and ambipolar SWNT thinfilm transistors (TFTs) is demonstrated for the first time. cop. 2014 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim.

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6 

Green's function for an infinite slot printed between two homogeneous dielectrics  Part I: Magnetic currents
This sequence of papers presents an analytical closed form for the Green's function of an infinite slot printed between two different homogeneous dielectrics. This first part is devoted to the derivation of the slot magnetic current and to the discussion of the relevant physical implications. The Fourier spectrum of the magnetic current is derived by solving in analytical form, under small width approximation, the integral equation (IE) representing the continuity of the magnetic field trough the slot axis. The accuracy of the result is validated trough a fine meshing Method of Moments. From the consequent spectral expression, a closed form approximation of the leakywave propagation and attenuation constants is derived. An asymptotic expression for the current is also obtained by steepest descent path evaluation of the pertinent spectral integral. Analytical expressions of the quasi static (reactive) contribution is given for both elementary dipole and delta gap excitations. The asymptotic, uniform closed form approximation for the field in every space point will be formulated and discussed in the second part of the paper.

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7 

Interpreting anomalies observed in oxide semiconductor TFTs under negative and positive bias stress
Oxide semiconductor thinfilm transistors can show anomalous behavior under bias stress. Two types of anomalies are discussed in this paper. The first is the shift in threshold voltage (VTH) in a direction opposite to the applied bias stress, and highly dependent on gate dielectric material. We attribute this to charge trapping/detrapping and charge migration within the gate dielectric. We emphasize the fundamental difference between trapping/detrapping events occurring at the semiconductor/dielectric interface and those occurring at gate/dielectric interface, and show that charge migration is essential to explain the first anomaly. We model charge migration in terms of the noninstantaneous polarization density. The second type of anomaly is negative VTH shift under high positive bias stress, with logarithmic evolution in time. This can be argued as electrondonating reactions involving H2O molecules or derived species, with a reaction rate exponentially accelerated by positive gate bias and exponentially decreased by the number of reactions already occurred.

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8 

Multi sector PCSEBG antenna for low cost high directivity applications
This work proposes a new topology of antenna based on the use of Planar Circular Symmetric EBG with different periodicities. These periodicities are used to impose different propagation velocities of the dominant surface waves on different zones of the same dielectric substrate. The control of the dispersion characteristics guides the design together with the definition of a centered feed suitable to excite the surface waves. One prototype has been designed, manufactured and tested to prove the concept. © 2007 IEEE.

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9 

1D Scanning Arrays on Dense Dielectrics Using PCSEBG Technology
We show how the design of integrated arrays can significantly benefit from planar circularly symmetric (PCS) electromagnetic band gap (EBG) structures. Using this technology, a phased array that scans up to 40° in one dimension and that is characterized by relatively large bandwidth (BW ≈ 15%) is designed, manufactured and tested. The specific advantages coming from the use of PCSEBGs are two fold. On one hand the losses associated to surface waves are significantly reduced. On the other hand each element of the array has a larger effective area that leads to a higher gain for the complete array when compared with a standard technology. Additional benefits are the low crosspolarization levels, the good front to back ratio considering that the antenna does not include a backing reflector, and the low profile. © 2007 IEEE.

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10 

Functionally graded ferroelectric polyetherimide composites for high temperature sensing
High temperature ferroelectrics for thermally stable devices that can detect pressure and temperature are of great industrial interest. Here we describe composites of lead titanate (PT) particlepolyetherimide (PEI) polymers with stable dielectric and piezoelectric properties over a broad range of temperature and frequency. The reported materials have a low dielectric loss (tanδ ∼ 0.001 at 1 kHz) and a high piezoelectric voltage coefficient of 100 mV m N1 at record temperatures of 175 °C. We demonstrate that a small ceramic loading leads to a significant change in thermally stable piezoelectric behavior, while the processability as well as mechanical properties remain comparable to those of the neat polymer. Careful design of the microstructure is performed by dielectrophoretic assembly of ferroelectric PT microparticles to induce microwire configurations, which is shown to be a key element in attaining high functionality at low ceramic loading. Thermal imidization of the composites is performed in two steps, first partial imidization at 60 °C to form free standing films containing polyamic acid, followed by full imidization at 200 °C and 300 °C. The presence of highly polar polyamic acid results in higher dielectric permittivity and electrical conductivity that facilitate efficient poling. Upon complete imidization of the films at 300 °C the dielectric and piezoelectric properties are tested at elevated temperatures. A fully imidized composite contains completely closed imide groups, resulting in a thermally stable material with a very low dielectric loss that maintains more than 85% of its room temperature piezoelectric sensitivity up to 175 °C. The room temperature piezoelectric voltage coefficient shows more than 400% improvement over that of PT ceramics.

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11 

Back End Monolithic Serial Interconnection Technology for CIGS with Shuntfree Laser Scribing and Inkjet Printing
Back end interconnection technology is presented for CIGS using laser scribing and inkjet printing of dielectric material. Shuntfree laser scribing of CIGS is shown, which is essential in the back end approach for monolithic serial interconnection. Full back end interconnected minimodules of 20x20cm2 were made and show no electrical losses compared to the reference cells. These results show the feasibility of complete module manufacturing after full area deposition of the CIGS stack, enabling cheaper and more flexible production of PV modules. © 2018 IEEE.

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