Complementary Metal-oxide Semiconductor Arrays Research Articles

Angular correction methodology and characterization of a high-resolution CMOS array for patient specific quality assurance on a robotic arm linac.

To develop an angular correction methodology and characterize a high-resolution complementary metal-oxide-semiconductor (CMOS) array for patient specific quality assurance on a robotic arm linear accelerator. Beam path files from the treatment planning software (TPS) were used to calculate the angle of radiation beam with respect to the detector plane. Beams from multiple discrete angles were delivered to the CMOS detector array and an angular dependency look up table (LUT) was created. The LUT was then used to correct for the angular dependency of the detector. An iso-centric 5mm fixed cone, non iso-centric multi-target fixed cone, 10mm Iris and a multi-leaf collimator (MLC) based collimated plan were delivered to the phantom and compared to the TPS with and without angular correction applied. Additionally, the CMOS array was compared to gafchromic film and a diode array. Large errors of up to 30% were observed for oblique angles. When angular correction was applied, the gamma passing rate increased from 99.2% to 100% (average gamma value decreased from 0.29 to 0.14) for the 5-mm iso-centric cone plan. Similarly, the passing rate increased from 84.0% to 100% for the Iris plan and from 49.98% to 98.4% for the MLC plan when angular correction was applied. For the multi-target plan, applying angular correction improved the gamma passing rate from 94% to 99.6%. The 5mm iso-centric fixed cone plan was also delivered to film, and the gamma passing rate was 91.3% when using gafchromic film as the reference dataset, whereas the diode array provided insufficient sampling for this plan. A methodology of calculating the beam angle based on the beam path files was developed and validated. The array was demonstrated to be superior to other quality assurance tools because of its sub-millimeter spatial resolution and immediate read out of the results.

High-Performance CMOS Inverter Array with Monolithic 3D Architecture Based on CVD-Grown n-MoS2 and p-MoTe2.

In thiswork, monolithic three-dimensional complementary metal oxide semiconductor (CMOS) inverter array has been fabricated, based on large-scale n-MoS2 and p-MoTe2 grown by the chemical vapor deposition method. In the CMOS device, the n- and p-channel field-effect transistors (FETs) stack vertically and share the same gate electrode. High k HfO2 is used as the gate dielectric. An Al2 O3 seed layer is used to protect the MoS2 from heavily n-doping in the later-on atomic layer deposition process. P-MoTe2 FET is intentionally designed as the upper layer. Because p-doping of MoTe2 results from oxygen and water in the air, this design can guarantee a higher hole density of MoTe2 . An HfO2 capping layer is employed to further balance the transfer curves of n- and p-channel FETs and improve the performance of the inverter. The typical gain and power consumption of the CMOS devices are about 4.2 and 0.11 nW, respectively, at VDD of 1V. The statistical results show that the CMOS array is with high device yield (60%) and an average voltage gain value of about 3.6 at VDD of 1 V. This work demonstrates the advantage of two-dimensional semi-conductive transition metal dichalcogenides in fabricating high-density integrated circuits.

Direct emission spectrometry determination of fluorine in carbon materials: Argon dc arc and spark radiation sources

In this work, the procedure for direct atomic emission spectrometry (AES) determination of fluorine impurities in carbon materials was proposed. Two types of simple radiation sources with direct solid (powdered) sample introduction were studied: direct current arc (25A) and high-power low voltage spark (300 V, of 2348 μF). For each source, standard graphite extra high purity electrodes and argon discharge atmosphere were used. Red spectral region approach to non-metal AES determination was employed with analytical line F I 685.603 nm. The spectra were registered by compact tunable fiber-optic spectrometer with linear complementary metal oxide semiconductor array (CMOS) sensor and short-focus lens. Special measures were taken to counter red spectral region interferences, such as CN molecular bands and thermal radiation. The excitation of F in both types of radiation source was studied. A set of artificial graphite and NaF based standards was prepared for calibration and evaluated by two independent approaches: indirect dc arc AES and water extraction photometry. Limit of detection was determined for dc arc source was 5 μg/g, and for spark 20 μg/g of F. The whole cycle of measurement with each type of radiation source takes 10 min. As the power of dc arc is limited by generator capabilities, it is possible that even lower limit of detection is achievable with higher discharge current.

A direct dc arc emission spectrometry determination of chlorine impurities in nuclear grade graphite

In the present study, the direct current arc atomic emission spectrometry (dc arc AES) method was proposed for direct determination of chlorine impurities in nuclear-grade graphites and graphite foils in the range of 1‐–100 ppm in order to meet nuclear power industry requirements. The procedure is based on near-infrared (NIR) AES approach for determination of non-metal impurities, contrary to the most common vacuum ultraviolet AES approach. Carbon dc arc in argon atmosphere was used as radiation source. This radiation source employs standard extra high purity 6 mm diameter standard shaped graphite electrodes and standard vertical spectroanalytic stand, but employs several improvements as well: special protective fused quartz tube, and specially built fiber optic refocuser. Registration of spectra was performed via a novel compact tunable spectrometer with linear complementary metal oxide semiconductor array (CMOS) detector. As the work in near-infrared spectral range is hampered by spectral interference factors, measures were taken to counter them. Due to specifics of the radiation source, the excitability of chlorine was studied both in air and argon in presence of carbon, as well as in its absence. Artificial standards for calibration of the spectrometer were prepared by mixing extra high purity NaCl and graphite powder and evaluated by two independent approaches: indirectly by dc arc AES determination of Na, and directly by water extraction and photometrical determination of Cl. The characteristics of evaporation and excitation in dc arc of chlorine from both standards and real nuclear graphite samples were studied due to the differences in the nature of chlorine source in them. The detection limit of was determined 0.8 μg/g. The whole cycle of measurement, including sample preparation is about 10 min.

Image pixel device using integrated organic electronic components

We report a solution processed, monolithically integrated device similar to an imaging pixel element used in complementary metal-oxide semiconductor (CMOS) based cameras. This integrated pixel essentially consists of a pair of organic photodiode (OPD) and organic field effect transistor (OFET). The signal generated by the light responsive OPD drives the OFET to different output states to quantify the light intensity. The prerequisite of a low operating voltage OFET (<2 V) was achieved using a bottom-gate, top-contact OFET consisting of a high mobility polymer semiconductor and a self-assembled hybrid dielectric layer. A bulk heterojunction blend was used as the photo-active layer in the OPD along with suitable buffer layers for charge extraction. The material parameters were optimized to realize a suitable structure which clearly demonstrated the interplay of the OPD and OFET operations, thereby forming a roadmap for all-organic CMOS arrays.

CMOS SPADs: Design Issues and Research Challenges for Detectors, Circuits, and Arrays

Solid-state single photon detectors are playing a significant role in the development of high-performance single-photon imaging systems for fluorescence lifetime imaging, time-of-flight positron emission tomography and Raman Spectroscopy applications. The main driving factors are the unparalleled levels of miniaturization and portability, low fabrication costs, and high overall performance resulting from the integration of single-photon avalanche diodes (SPADs) with mixed-signal circuits in deep-submicron (DSM) complementary metal-oxide-semiconductor (CMOS) technology. At the heart of such imaging systems is the SPAD, capable of single-photon sensitivity and sub-nanosecond time resolution, and its associated circuitry, which in DSM CMOS, is capable of high-speed, low-power mixed-mode signal processing. In this paper, we review and discuss the most recent developments in DSM CMOS SPAD detectors, circuits and arrays and investigate issues of scalability, miniaturization and performance trade-offs involved in designing SPAD imaging systems. Design considerations, research challenges, and future directions for CMOS SPAD image sensors will be highlighted and addressed.

CMOS arrays as chemiluminescence detectors on microfluidic devices

A simple, low-cost process to integrate complementary metal oxide semiconductor array detectors (CMOSAD) for chemiluminescence is presented, evaluated, and applied to the determination of nitrite in ground water samples. CMOS arrays of different brands (obtained from commercial image sensors) were adapted as chemiluminescence detectors on microfluidic devices. The performance of the CMOSADs was evaluated in the visible zone of the spectrum using a tungsten halogen lamp as light source. Intrinsic parameters assessed included signal stability, spectral response, dark current, and signal-to-noise ratio. Thereafter, the CMOSADs were integrated on microfluidic devices and their performances in quantitative analysis were assessed with the chemiluminometric reaction of hydrogen peroxide with luminol, catalyzed with hexacyanoferrate (III). The parameters assessed were sensitivity, linear range, detection limit, reproducibility, correlation coefficient of the calibration curves, and baseline drift during measurements. The CMOSAD with the best performance was selected to assess the applicability of the developed microfluidic devices with the integrated detector. The microfluidic system permitted the determination of nitrite with both good precision and good recovery values in the analysis of ground water samples. Integration was easily achieved and enabled the development of a simple, low-cost, and feasible alternative to conventional detectors.

Image Quality Evaluation of a Highly-Integrated Digital X-ray Imaging Sensor for Dental Intraoral-Imaging Applications

We have developed a highly-integrated digital X-ray imaging sensor based upon a complementarymetal-oxide semiconductor (CMOS) array coupled with a columnar CsI(Tl) scintillator and an X-ray conversion fiberoptic plate for dental intraoral-imaging applications. The sensor consists of a commercially-available CMOS array with a 35 μm × 35 μm pixel size and a 24.1 mm × 31.6 mm active area, and a high-efficiency columnar CsI(Tl) scintillator of 90 μm in thickness directly deposited on a fiberoptic plate of a 6 μm in core size and 1.45 mm in thickness. In this paper, we describe the highly-integrated digital X-ray imaging sensor and evaluate its performance in terms of the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE), as indicators of image quality.

Chemical Sensing Systems Using Xerogel-Based Sensor Elements and CMOS Photodetectors

We present the first example of an integrated complementary metal-oxide-semiconductor (CMOS) photodetector coupled with a solid-state xerogel-based thin-film sensor to produce a compact chemical sensor system. We compare results using two different CMOS-based detector systems to results obtained by using a standard photomultiplier tube (PMT) or charge-coupled device (CCD) detector. Because the chemical sensor elements are governed by a Stern-Volmer relationship, the Stern-Volmer quenching constant is used as the primary comparator between the different detectors. All of the systems yielded Stern-Volmer constants from 0.042 to 0.049 O/sub 2/%/sup -1/. The results show that the CMOS detector system yields analytical data that are comparable to the CCD- and PMT-based systems. The disparity between the data obtained from each detector is primarily associated with the difference in how the signals are obtained by each detector as they presently exist. We have also observed satisfactory reversibility in the operation of the sensor system. The CMOS-based system exhibits a response time that is faster than the chemical sensor element's intrinsic response time, making the CMOS suitable for time-dependent measurements. The CMOS array detector also uses less than 0.1% the power in comparison to a standard PMT or CCD. The combined xerogel/CMOS system represents an important step toward the development of a portable, efficient sensor system.

DEVELOPMENTS AND APPLICATIONS OF HIGH-PERFORMANCE CCD AND CMOS IMAGING ARRAYS

▪ Abstract For over 20 years, charge-coupled devices (CCDs) have dominated most digital imaging applications and markets. Today, complementary metal oxide semiconductor (CMOS) arrays are displacing CCDs in some applications, and this trend is expected to continue. Low cost, low power, on-chip system integration, and high-speed operation are unique features that have generated interest in CMOS arrays. This paper reviews current CCD and CMOS sensor developments and related applications. We compare fundamental performance parameters common to these technologies and describe why the CCD is considered a mature technology, whereas CMOS arrays have significant room for growth. The paper presents custom CMOS pixel designs and related fabrication processes that address performance deficiencies of the CCD in high-performance applications. We discuss areas of development for future CCD and CMOS imagers. The paper also briefly reviews hybrid imaging arrays that combine the advantages of CCD and CMOS, producing better sensors than either technology alone can provide.