Anode Layout Research Articles

Photoelectrochromic Devices with Enhanced Power Conversion Efficiency.

In the present work, we propose a new architecture for partly covered photoelectrochromic devices with a modified anode layout, so that the TiO2 film is deposited first on the substrate, covering a small part of its surface, followed by the WO3 film that covers the remaining device area. As a result, the TiO2 film can be subjected to the proper thermal and chemical treatment without affecting the electrochromic performance of the WO3 film. The proposed design led to photoelectrochromic (PEC) devices with a power conversion efficiency (PCE) four times higher than that of typical partly covered devices, with a measured maximum of 4.9%. This, in turn, enabled a reduction in the total area covered by the photovoltaic unit of the devices by four times (to 5% from 20%), thus reducing its visual obstruction, without affecting the depth, uniformity and speed of coloration. A detailed study of the parameters affecting the performance of the new devices revealed that, with the cover ratio decreasing, PCE was increasing. The photocoloration efficiency also exhibited the same trend for cover ratio values below 15%. Storage of the devices in short circuit conditions was found to accelerate optical reversibility without affecting their photovoltaic and optical performance.

Digital performance improvements of a CdTe pixel detector for high flux energy-resolved X-ray imaging

Photon counting detectors with energy resolving capabilities are desired for high flux X-ray imaging. In this work, we present the performance of a pixelated Schottky Al/p-CdTe/Pt detector (4×4) coupled to a custom-designed digital readout electronics for high flux measurements. The detector (4×4×2mm3) has an anode layout based on an array of 16 pixels with a geometric pitch of 1mm (pixel size of 0.6mm). The 4-channel readout electronics is able to continuously digitize and process the signals from each pixel, performing multi-parameter analysis (event arrival time, pulse shape, pulse height, pulse time width, etc.) even at high fluxes and at different throughput and energy resolution conditions. The spectroscopic response of the system to monochromatic X-ray sources, at both low and high rates, is presented with particular attention to the mitigation of some typical spectral distortions (pile-up, baseline shifts and charge sharing). At a photon counting rate of 520kcps/pixel, the system exhibits an energy resolution (FWHM at 59.5keV) of 4.6%, 7.1% and 9% at throughputs of 0.9%, 16% and 82%, respectively. Measurements of Ag-target X-ray spectra also show the ability of the system to perform accurate estimation of the input counting rate up to 1.1Mcps/pixel.The aim of this work is to point out, beside the appealing properties of CdTe detectors, the benefits of the digital approach in the development of high-performance energy resolved photon counting (ERPC) systems for high flux X-ray imaging.

Influence of Anode Layout on the Performance of SiC JBS Diodes

Various layouts of the anode of Junction Barrier Schottky (JBS) diodes are compared theoretically and it is found that the hexagonal honeycomb structure with 3-D symmetry offers the best figure of merit (FOM). Proportional relationships between the various layouts are reported, using which we extend a fully analytical 2-D model for reverse biased field shielding in a JBS diode to the superior 3-D layouts. The effect of reducing implanted feature size is also analyzed as a trade-off between FOM and breakdown voltage capability.

Advanced data readout technique for Multianode Position Sensitive Photomultiplier Tube applicable in radiation imaging detectors

Most of the best performing PSPMT tubes from Hamamatsu and Burle are designed with a pad-matrix anode layout. However, for obtaining a high resolution, a small-sized anode photomultiplier tubes are preferable; these tubes may have 64, 256 or 1024 anodes per tube. If the tubes are used in array to get a larger area detector, the number of analog channels may range from hundreds to thousands. Multichannel analog readout requires special electronics ICs, ASICs etc., which are attached to multichannel DAQ system. As a result, the data file and data processing time will be increased. Therefore, this readout could not be performed in a small project. Usually, most of radiation imaging applications allow the use of analog data processing in front-end electronics, significantly reducing the number of the detector's output lines to data acquisition without reducing the image quality. The idea of pad-matrix decoupling circuit with gain correction was invented and intensively tested in JLab. Several versions of PSPMT readout electronics were produced and studied. All developments were done and optimized specifically for radiation imaging projects. They covered high resolution SPECT, high speed PET, fast neutron imaging, and single tube and multi tube array systems. This paper presents and discusses the summary of the observed results in readout electronics evaluation with different PSPMTs and radiation imaging systems, as well as the advantages and limitations of the developed approach to radiation imaging detectors readout.

BIDIRECTIONAL FLOATING-BASE BJT ESD PROTECTED RFID CHIP

ABSTRACT The maximum peak-to-peak radio frequency (RF) signal antenna voltage level can be extended to reach to over 12 Vpp, −6 V to +6 V. Thus it is desirable that the electro-static discharge (ESD) device does not turn on at the normal operating RF antenna signal voltage level. The turn-on threshold negative voltage of the ESD device of the PN diode type is around −0.5 V in the conventional radio frequency identification (RFID) chip. The asymmetric threshold voltage characteristics of the ESD device of the RFID chip makes the distortion of the RF antenna signal at the high intensity RF input field. In the proposed floating base vertical PNP ESD device, N-type doped N-WELL floating base is sandwiched between two p-type P+ emitter and P-WELL collector. Floating base BJT ESD device enhances the performance of parasitic BJT current in the ESD mode. During the negative voltage phase of RF antenna input signal, the negative voltage of RF antenna input is extended to around −10 V. This extension of RF antenna input operation voltage range makes to prevent from any distortion of RF antenna signal at the high RF input field. The measured HBM ESD protection level of the floating base BJT ESD device is over 2000 V with the P+ anode layout area of 400 μm2.

Influence of shielded insoluble anode layout on the consumption of bath additives

The benefi ts of anode shielding, either physically by an inert grid placed above the anode or by a grid electrically connected to the anode, are reviewed. During operation in practice and in laboratory investigations with a range of plating solutions, shielding has been found to reduce additive consumption and hence the need for bath regeneration, to reduce the effect on the active layer in pulse plating reverse mode, to reduce oxidation of cations, and to increase stability of performance over the life of the anode.

FLOATING-BASE BJT TYPE ESD DEVICE FOR RFID CHIP

ABSTRACT N-WELL floating base is sandwiched between P+ emitter and P-WELL collector in the proposed floating base vertical PNP electro-static discharge (ESD) protection device. Floating base bipolar junction transistor (BJT) ESD protection device increases the current performance of the parasitic BJT in the ESD mode. During the negative voltage phase of RF antenna signal, the negative voltage range of RF antenna signal is extended to around −10 V at the high RF power field without latch-up failure. The minimum P+ anode layout area of the floating base type BJT ESD device is 400 μm2 for the target ESD voltage of 2000 V in human body model (HBM) mode. The parasitic capacitance of the floating base type BJT ESD protection device is about 0.4 pF. The layout area of the proposed floating base type BJT ESD protection device is 50% smaller that of the conventional NMOS diode type ESD protection device for the target ESD voltage of 2000 V in HBM mode. The rewards of the floating base type BJT ESD device will come in the form of improved yields, higher reliability, and substantially lower costs of RFID chip manufacturing.

Hard x-ray response of pixellated CdZnTe detectors

In recent years, the development of cadmium zinc telluride (CdZnTe) detectors for x-ray and gamma ray spectrometry has grown rapidly. The good room temperature performance and the high spatial resolution of pixellated CdZnTe detectors make them very attractive in space-borne x-ray astronomy, mainly as focal plane detectors for the new generation of hard x-ray focusing telescopes. In this work, we investigated on the spectroscopic performance of two pixellated CdZnTe detectors coupled with a custom low noise and low power readout application specific integrated circuit (ASIC). The detectors (10×10×1 and 10×10×2 mm3 single crystals) have an anode layout based on an array of 256 pixels with a geometric pitch of 0.5 mm. The ASIC, fabricated in 0.8 μm BiCMOS technology, is equipped with eight independent channels (preamplifier and shaper) and characterized by low power consumption (0.5 mW/channel) and low noise (150–500 electrons rms). The spectroscopic results point out the good energy resolution of both detectors at room temperature [5.8% full width at half maximum (FWHM) at 59.5 keV for the 1 mm thick detector; 5.5% FWHM at 59.5 keV for the 2 mm thick detector) and low tailing in the measured spectra, confirming the single charge carrier sensing properties of the CdZnTe detectors equipped with a pixellated anode layout. Temperature measurements show optimum performance of the system (detector and electronics) at T=10 °C and performance degradation at lower temperatures. The detectors and the ASIC were developed by our collaboration as two small focal plane detector prototypes for hard x-ray multilayer telescopes operating in the 20–70 keV energy range.

Spectroscopic response of a CdZnTe multiple electrode detector

The spectroscopic performances of a CdZnTe detector (crystal size: 5×5×0.9 mm 3) with five electrodes (cathode, anode and three steering electrodes) were studied. The anode layout, which consists of a circular electrode ( φ=80 μm) surrounded by two ring electrodes (gap=100 μm; radial width Δ r=100 μm) and by one electrode that extends to the edge of the crystal, is mostly sensitive to the electron carriers, overcoming the well known effect of the hole trapping in the measured spectra. We report on the spectroscopic response of the detector at different bias voltages of the electrodes and at various photon energies ( 109Cd, 241Am and 57Co sources). The CdZnTe detector exhibits excellent energy resolution (0.87 keV FWHM at 22.1 keV, 1.15 keV FWHM at 59.5 keV and 1.91 keV FWHM at 122.1 keV; working temperature −10 °C) and low tailing (FW.1M to FWHM ratio of 1.87 at 22.1 keV, 1.93 at 59.5 keV and 2.01 at 122.1 keV). This study stresses on the excellent spectroscopic properties and the stability of the CdZnTe detectors equipped with a custom anode layout. Furthermore, the obtained results make such detectors very attractive candidates as X-ray spectrometers mainly for medical applications.

A novel readout concept for multianode photomultiplier tubes with pad matrix anode layout

We have developed a new analog readout concept for multianode photomultiplier tubes with a pad matrix anode layout. This new readout technique is the result of a modification of a technique previously developed at the Detector Group of Jefferson Lab, (V. Popov, US patent No: 6,747,263 B1) [V. Popov, S. Majewski, A.G. Weisenberger, Readout Electronics for Multianode Photomultiplier Tubes with Pad Matrix Anode Layout, Thomas Jefferson National Accelerator Facility, IEEE 2003 Medical Imaging Conference Record, November 2003]. The new analog readout circuit provides the same analog conversion of matrix 2-D output into X and Y projective output with a significant reduction of analog outputs. The old readout network consists of resistors’ matrix and current collecting amplifiers, and it provides decoupling of each anode output into two directions (one to X and one to Y coordinates), but a decoupling function that is carried out independent of photomultiplier tube gains nonuniformity. A newly developed readout network (US patent pending) also consists of resistors’ matrix and current collecting amplifiers, but the new matrix includes an additional dumping resistor that provides an excess current from anode pad grounding. As a result, we subtract an extra current of high-gain pads in order to move the pads gain to an absolute minimum value for a given photomultiplier tube. This gain equalization procedure reduces image distortion related to gain nonuniformity. The new readout technique was used in several new radiation imaging detectors designed in the Detector Group of Jefferson Lab. It shows a visible readout uniformity and linearity improvement. The test results of an initial evaluation of this readout that is applied for data readout of four H8500 Hamamtsu PSPMT are presented.