High FOM Research Articles

ScAlN-Based LCAT Mode Resonators Above 2 GHz With High FOM and Reduced Fabrication Complexity

This letter reports the first implementation of a new class of laterally coupled alternating thickness (LCAT) mode resonators operating above 2 GHz, realised by replacing the bottom interdigitated electrodes of the conventional LCAT mode resonator with an electrically floating plate. Besides saving one mask process and relaxing the tight resolution and alignment requirements for defining small features, the flat unpatterned bottom electrode metal is also more favorable for the growth of highly oriented piezoelectric thin film, which results in an improved resonator quality factor (Q). A group of 8% scandium doped aluminium nitride-based modified LCAT mode resonators with frequency difference over 100 MHz by varying the top interdigitated electrode pitches are fabricated achieving coupling coefficient (k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) of up to 6.45% and figure of merit of up to 54, making them promising candidates for integrated band selection filter banks.

Wide-angle infrared metamaterial absorber with near-unity absorbance

A wide-angle infrared perfect metamaterial absorber is experimentally verified. The perfect metamaterial absorber shows polarization-independent at normal incidence and displays high absorption rate at a large angle of incidence. The absorption property of the proposed metamaterial absorber is sensitive to the change of refractive index of environmental mediums. An absorption sensor scheme is proposed by combining the concept of the perfect metamaterial absorber and the variation of the refractive index of the environmental medium. Measured results indicate that the proposed absorption sensor scheme achieves high FOM values with different surrounding mediums (air, water, and glucose solution).

Simulation design of high reverse blocking high-K/low-K compound passivation AlGaN/GaN Schottky barrier diode with gated edge termination

In this paper, a novel high-K/low-K compound passivation AlGaN/GaN Schottky Barrier Diode (CPG-SBD) is proposed to improve the off-state characteristics of AlGaN/GaN schottky barrier diode with gated edge termination (GET-SBD) by adding low-K blocks in to the high-K passivation layer. The reverse leakage current of CPG-SBD can be reduced to 1.6 nA/mm by reducing the thickness of high-K dielectric under GET region to 5 nm, while the forward voltage and on-state resistance keep 1 V and 3.8 Ω mm, respectively. Breakdown voltage of CPG-SBDs can be improved by inducing discontinuity of the electric field at the high-K/low-K interface. The breakdown voltage of the optimized CPG-SBD with 4 blocks of low-K can reach 1084 V with anode to cathode distance of 5 μm yielding a high FOM of 5.9 GW/cm2. From the C-V simulation results, CPG-SBDs induce no parasitic capacitance by comparison of the GET-SBDs.

Effect of the incident power on permittivity, losses and tunability of BaSrTiO3 thin films in the microwave frequency range

Domain wall motions in ferroelectrics participate to the material's complex permittivity and are responsible for their sensitivity of the dielectric properties to the driving electric field and thus to the incident power at microwave frequencies. In the present study, the dependence of the permittivity, the dielectric losses, and the tunability of Ba2∕3Sr1∕3TiO3 (BST) thin films on the incident power and on the bias fields is examined at a frequency of 500 MHz. While the domain wall motion participates only slightly to the permittivity (&amp;lt;5%), it strongly influences the losses due to its very dissipative behavior. As a consequence, the Figure of Merit (FoM, the ratio between tunability and dielectric losses) of the material depends on the applied microwave power. In the present study, a decrease in the FoM from 29 to 21 is observed for an incident power varying from –20 dBm to 5 dBm. When characterizing ferroelectric materials, the incident power has to be considered; moreover, domain wall motion effects should be limited in order to achieve a high FoM and less power sensitivity.

Numerical investigations of a near-infrared plasmonic refractive index sensor with extremely high figure of merit and low loss based on the hybrid plasmonic waveguide-nanocavity system.

With vertically slotted hybrid plasmonic waveguides (VSHPWs)-nanocavity system fabricated on the silicon-on-insulator platform, a near-infrared surface plasmon resonances (SPRs)-based refractive index (RI) sensor with extremely high figure of merit FOM = 224.3 and transmission efficiency T = 97.6% is proposed and investigated. Based on the finite element method, effective mode index behaviors together with spectral properties are calculated to analyze and optimize the sensing performance. Within near-infrared region, the wavelength sensitivity (S) and optical resolution (FWHM) can be achieved as S = 1817.5nm/RIU and FWHM = 7.4nm. A mechanism of synergy between propagating SPRs and localized SPRs is also presented for further improving the sensitivity (as high as 2647.5nm/RIU). In addition, the VSHPWs-based RI sensor can be fully realized by CMOS-compatible fabrication technology. In general, the high FOM, S and T achieved by our designed structure may have extensive applications in nanophotonic circuits, environmental monitoring and even pharmaceutical research.

A low power CMOS VCO using inductive-biasing with high performance FoM**Project supported by the National Science and Technology Major Project of China (No. 2011ZX03004-002-01).

A novel voltage-controlled oscillator (VCO) topology with low voltage and low power is presented. It employed the inductive-biasing to build a feedback path between the tank and the MOS gate to enhance the voltage gain from output nodes of the tank to the gate node of the cross-coupled transistor. Theoretical analysis using time-varying phase noise theory derives closed-form symbolic formulas for the 1/f2 phase noise region, showing that this feedback path could improve the phase noise performance. The proposed VCO is fabricated in TSMC 0.13 μm CMOS technology. Working under a 0.3 V supply voltage with 1.2 mW power consumption, the measured phase noise of the VCO is −119.4 dBc/Hz at 1 MHz offset frequency from the carrier of 4.92 GHz, resulting in an FoM of 192.5 dBc/Hz.

Artificial magnetism of cross shaped metamaterial in green light frequencies

We theoretically investigate the magnetic response of a cross-shaped metamaterial at green light frequencies. Such a structure supports a strong magnetic resonance, which results in a large negative permeability and hence a band of negative refractive index over 50THz. The structure is low loss and exhibits a high FOM of 3.75 at 570THz. The magnetic resonance can be effectively tailored both in operation frequency and resonance strength by means of adjusting the geometric dimensions, which is well described by the equivalent circuit model. The proposed structure may offer an effective means to realize the magnetic devices at visible frequencies.

Serovars and Drug-Resistance of Salmonella Strains Isolated from Domestic Chicken Meat in Tokyo (1992-2012)

A total of 477 Salmonella strains isolated from retail domestic chicken meat during 1992-2012 in Tokyo, were examined regarding their serovars and drug-resistance. These strains were detected in 469 (29.8%) of 1,576 samples. The detection rate in every two years was 10.1% to 46.3% of the range. Serological typing results showed that 477 strains were classified into 22 serovars excepting 2 untypable strains. Among them, S. Infantis (312 strains) was the most prevalent, followed by II O4: b: [e, n, x] (S. II Sofia) (71 strains), S. Hadar (20 strains), S. Typhimurium (20 strains), S. Manhattan (12 strains), S. Schwarzengrund (9 strains), S. Agona (7 strains), and other 15 serovars (24 strains). Results of the antibacterial drug susceptibility test for 477 strains revealed that 89.9% was resistant to some of the 12 drugs tested, and multidrug-resistant strains accounted for 90.2% among them. The frequencies of resistance to each drug were 81.8%; 77.8%, 45.5%, 33.3%, 11.3%, 9.6%, 2.9%, 0.6%, 0.6% and 0.2%, in order with high frequency, for SM, TC, KM, ST, NA, ABPC, CP, FOM, CTX and CAZ, respectively. None of the strains was resistant to NFLX or IPM. Three CTX-resistant strains were CTX-M type extended-spectrum β-lactamase (ESBL) producers, and the group of CTX-M type ESBL genes were CTX-M-2 group (2 strains) and CTX-M-9 group (1 strain). CAZ-resistant 1 strain was an ESBL producer, but the ESBL gene was not determined.

A 10 bit 1 GSPS Nyquist DAC in 180 nm CMOS with high FOM

A new segmented architecture is presented to improve the dynamic and static performance of the current steering digital-to-analog converters (DACs). In the proposed architecture instead of a single...

Optimization of a multiple-scattering Compton camera as a photon-tracking imager for 6-MV photon therapy

During radiation therapy, the irradiated position and the energy deposited in a patient must be monitored. In general, calculations before photon exposure or 2D measurements of the transmitted photons have been widely used for making dose estimates. In this paper, we propose a real-time 3D dose measurement using Compton imaging technology. On the basis of the Monte-Carlo method, we designed a multiple-scattering Compton camera system (MSCC) with semiconductor and scintillation detectors. The MSCC was constructed with two semiconductor detectors as scattering detectors and a cadmium-tungstate (CWO) scintillator detector as an absorber detector. The two planar semiconductor arrays, and the CWO array consisted of 40 × 40 pixels, each with a size of 1 × 1 × e mm3, where e is the variable thickness of the detectors. The design parameters, such as the types of semiconductors, detector thicknesses and distances between detectors, were optimized on the basis of the detection efficiency and angular resolution of reconstructed images for a point source. Under the optimized conditions, uncertainty factors in geometry and energy were estimated for various inter-detector distances. We used a source corresponding to photons scattered from a water phantom exposed to 6-MeV peak X-rays. According to our simulation results, the figure of merit, reached its maximum value when the inter-detector distance was 3 cm. In order to achieve a high FOM, we chose 1 cm as the optimum thickness for the scattering and absorbed detectors. A cadmium-zinc-telluride (CZT) detector showed the best performance among the simulated semiconductors. The position uncertainty caused by the pixelization effect was the major factor in degrading the angular resolution of the reconstructed images, and the degradation caused by energy broadening was less than expected. The angular uncertainties caused by Doppler broadening and incorrect sequencing were minimal compared with that of pixelization. Our simulation showed the feasibility of using the semiconductor-based Compton camera to monitor the exposed dose in 3D radiation therapy.

A 10 bit 1 GSPS Nyquist DAC in 180 nm CMOS with high FOM

A new segmented architecture is presented to improve the dynamic and static performance of the current steering digital-to-analog converters (DACs). In the proposed architecture instead of a single binary DAC, distributed binary cells are used. So the effect of the mismatch and timing errors of the binary cells are not accumulated and are averaged out. For realization of the MSB unit cells those binary cells are reused to form the larger weighted unit cells. Realization of the MSB unit cells with smaller cells results in improved dynamic performances as the effects of gradient errors are minimized and the effects of nonlinear parasitic capacitances are reduced. The DAC has been designed in 180 nm five-metal nwell CMOS process. The simulation results show that the DAC can achieve a maximum spurious free dynamic range (SFDR) of 70.99 dB at 2.93 MHz signal for a sampling rate of 1 GSPS considering the mismatch effects. For 1 GSPS sampling rate the simulated Nyquist SFDR is >70 dB with mismatch. The simulated third order intermodulation distortion (IM3) of the DAC with mismatch effect is 71.40 dB, for a dual tone test with 491.21 and 495.12 MHz signals. The DAC is optimized for digital signal synthesis applications in wireless base stations and other communication applications. The power dissipation of the DAC is 78.21 mW at 498.05 MHz signal for a sampling rate of 1 GSPS with 1.8 V supply.

Design of self-bias tail transistor technique for low phase noise CMOS VCO with harmonic suppression using capacitance ground

This paper presents a low phase noise wideband CMOS VCO based on the self-bias tail transistor technique and harmonic suppression using a capacitance ground. This VCO utilizes switching capacitor arrays in which four channels are able to be selected for multi-band application. Moreover, the design of CMOS VCO makes good use of the self-bias tail transistor and capacitance ground filter technique to reduce the phase noise. The MOS varactors are used as fine tuning for wideband operating application. The fully integrated VCO provides excellent performance with high FOM −193dBc/Hz. The bandwidth of the frequency is 1.1GHz and the tuning range is 13.8%. The power dissipation of the core circuit is 8.28mW under a 1.8V supply and phase noise is measured as low as −123.6dBc/Hz at 1MHz offset under 8.5GHz oscillation frequencies. This VCO was made by the TSMC 0.18μm 1P6M CMOS standard process and the chip area is 0.75×0.69 (mm2).

Universal trench design method for a high-voltage SOI trench LDMOS

The design method for a high-voltage SOI trench LDMOS for various trench permittivities, widths and depths is introduced. A universal method for efficient design is presented for the first time, taking the trade-off between breakdown voltage (BV) and specific on-resistance (Rs,on) into account. The high-k (relative permittivity) dielectric is suitable to fill a shallow and wide trench while the low-k dielectric is suitable to fill a deep and narrow trench. An SOI LDMOS with a vacuum trench in the drift region is also discussed. Simulation results show that the high FOM BV2/Rs,on can be achieved with a trench filled with the low-k dielectric due to its shortened cell-pitch.

An 11 GHz low‐phase‐noise voltage‐controlled oscillator

PurposeThe purpose of this paper is to design a low phase noise and high figure of merit, fully integrated, voltage‐controlled oscillator (VCO) which was fabricated in TSMC CMOS 0.18‐μm 1P6M process.Design/methodology/approachA differential PMOS cross‐coupled architecture VCO with the capacitive feedback technology was designed to increase the linearity of frequency tuning range and decrease the phase noise. Varactor determining the performance of tuning range is also a key component in the design of VCO. The authors adopt the accumulation‐mode MOS varactor. The output spectrum and the phase noise are measured by E5052A spectrum analyzer.FindingsThe VCO is successfully fabricated in TSMC RF CMOS 0.18um 1P6M process. The measured tuning range is from 10.875 GHz ∼ 11.1 GHz with control voltage from 0 to 1.5 V. The measured phase noise is as low as −120.42 dBc/Hz at 1 MHz offset and the high FOM is −189.5 dBc/Hz. The output spectrum is −10.51dBm with center oscillator frequency of 10.942 GHz. The core circuit without buffer consumes power of 15 mW from a 1.8 V supply voltage.Originality/valueThis paper shows a fully integrated CMOS LCVCO architecture using capacitive feedback technology with low phase noise and high figure of merit for OC‐192 SONET applications.

Optimizing low loss silver nanowires structure metamaterial at yellow light spectrum with differential evolution

A double negative NIM composed of silver nanowires structure at visible light spectrum with high FOM and low loss was presented in this Letter. The geometrical parameters of silver nanowires were optimized by differential evolution (DE) to decrease the transmission loss to the greatest degree. By using numerical simulation of a wedge-shaped model and S-parameter retrieval method, we found that the DE-designed silver nanowires structure can exhibit a low loss LH frequency band at the yellow-light wavelength of 595 nm with the FOM of 45.8, that means it may have practical applications because of its low loss and high transmission.

A novel structure for double negative NIMs towards UV spectrum with high FOM

A novel ring structure is proposed for double negative NIMs at visible light spectrum with high FOM (e.g. about 11 at a wavelength of 583 nm) and low loss. Besides the effective medium theory, an equivalent circuit model is also given to explain physically why our novel structure can give double negative behavior with low loss. Adapted from the original ring structure, two other types of structures, namely, disk and nanowire structures, are also given to further push double negative NIMs toward ultraviolet (UV) spectrum.

Processing and Properties of Ba0.5Sr0.5TiO3/Bi1.5Zn1.0Nb1.5O7/Ba0.5Sr0.5TiO3 Sandwich Thin Films for Tunable Microwave Devices

Ba0.5Sr0.5TiO3/Bi1.5Zn1.0Nb1.5O7/Ba0.5Sr0.5TiO3 (BST/BZN/BST) sandwich films have been prepared by a sol-gel method. The sandwich thin films were deposited alternatively by spin coating technique and crystallized by rapid thermal annealing. The structures and morphologies of BST/BZN/BST sandwich thin films were analyzed by XRD and FESEM. The XRD results show that the cubic pyrochlore BZN phase and the perovskite BST phase can be observed in the sandwich thin films annealed at 750°C. The diffraction pattern confirms that no measurable reaction occurred between the BST and BZN phases during the annealing process. The surface of sandwich thin films is compact and crack-free. The BST/BZN/BST sandwich thin films annealed at 750°C exhibit a moderate dielectric constant around 91, a low loss tangent of 0.011, and a relative tunability of 27% at a bias field of 600 kV/cm at 10 kHz. Meanwhile, the FOM (defined as the ratio of tunability and loss tangent at room temperature) of BST/BZN/BST sandwich thin films is 24.5. The relative large dielectric constant, low loss tangent, and high FOM suggest that BST/BZN/BST sandwich thin films have potential application for tunable microwave device applications.

Superefficient thin film multilayer catalyst for generating hydrogen from sodium borohydride

A multilayer catalyst consisting of a electrophoretically deposited thin film of carbon nanotubes (CNTs) on a substrate of carbon fibers, followed by a coating of polymer-derived silicon carbonitride (SiCN), which is then decorated with a monolayer of transition metals is shown to perform at the upperbound of the phenomemological prediction from an earlier work [1]. A figure-of-merit for first order kinetics is equal to 4600 L min −1 [NaBH 4] −1 g met −1, which is nearly 30 times the value reported in literature, is achieved. This high FOM is attributed to the CNT-thin film, as opposed to the thick CNT-paper used in previous work, thus needing merely 0.15 wt% quantities of precious metals for effective catalysis. This new architecture corroborates the concepts that: (i) the catalytic activity derives mainly from the surface of the CNT substrate, and (ii) the silicon carbonitride interlayer is instrumental in dispersing the transition metals into a monolayer. The hydrogen generation rate (HGR) for zero order kinetics, which is obtained when [NaBH 4] > 0.03 M, is measured to be 75 L min −1 g met −1, which is among the higher values reported in the literature. The present multilayer catalysts are able to perform without fading for many cycles, presumably because the bondings in the substrate are predominantly covalent. This feature adds further uniqueness to this multilayer catalyst.

An Amplitude-Balanced Current-Reused CMOS VCO Using Spontaneous Transconductance Match Technique

A 3.5 GHz, 0.18 mum CMOS current-reused voltage-controlled oscillator (VCO) with very high amplitude balance is presented. While the current-reused VCO can dramatically save dc power consumption, it has the drawback of output amplitude imbalance resulting from the asymmetric circuit structure. A spontaneous transconductance match (STM) technique is proposed to balance the transconductance of nMOS and pMOS transistors by the imbalance-induced voltage at the center-tapped point of the tank inductor. This transconductance match takes place spontaneously with the occurrence of signal imbalance such that imbalances can be instantly eliminated. The measured amplitude imbalance ratio is less than 0.7% over the entire tuning range of 2.93 to 3.62 GHz, significantly reduced from 3% of the VCO without STM. The power consumption is as low as 1.65 mW from a 1.5 V supply. The phase noise is -122 dBc/Hz at 1 MHz offset. A very high FOM of -195.7 dBc/Hz is achieved.

A CMOS Backgate-Coupled QVCO Based on Back-to-Back Series Varactor Configuration for Minimal AM-to-PM Noise Conversion

A 3.3 GHz CMOS quadrature voltage-controlled oscillator (QVCO) with very low phase noise is presented. The back-to-back series varactor configuration is employed in the LC tank for minimizing the AM-to-PM noise conversion. The backgate coupling for quadrature phase inter-locking further eliminates the noise contribution from coupling transistors and also reduces power consumption. The implemented QVCO in 0.18 mum CMOS technology achieved very low phase noise of -133 dBc/Hz at 1 MHz offset, where the total power consumption is 4.4 mW from a 1.0 V supply. The chip has a very high FOM of -196.6 dBc/Hz.