Study of plasma charging-induced white pixel defect increase in CMOS active pixel sensor

Plasma process-induced “white pixel defect” (WPD) of CMOS active pixel sensor (APS) is studied for Si3N4 spacer etch back process by using a magnetically enhanced reactive ion etching (MERIE) system. WPD preferably takes place at the wafer edge region when the magnetized plasma is applied to Si3N4 etch. Plasma charging analysis reveals that the plasma charge-up characteristic is well matching the edge-intensive WPD generation, rather than the UV radiation. Plasma charging on APS transfer gate might lead to a gate leakage, which could play a role in generation of signal noise or WPD. In this article the WPD generation mechanism will be discussed from plasma charging point of view.     

GaN-based PIN alpha particle detectors

GaN-based PIN alpha particle detectors are studied in this article. The electrical properties of detectors have been investigated, such as current-voltage (I-V) and capacitance-voltage (C-V). The reverse current of all detectors is in nA range applied at 30 V, which is suitable for detector operation. The charge collection efficiency (CCE) is measured to be approximately 80% but the energy resolution is calculated to be about 40% mostly because the intrinsic layer is not sufficiently thick enough.     

Characterisation of a monolithic active pixel sensor for electron detection in the energy range 10–20 keV

As part of a feasibility study into the use of novel electron detectors for X-ray photoelectron emission microscopes (XPEEM), we have characterised the imaging performance of a back-illuminated monolithic active pixel sensor (MAPS) operating under both integrating and counting modes for electrons in the energy range 10–20 keV. For integrating mode, we present the detective quantum efficiency (DQE), which shows marked improvements over conventional indirect detectors based on microchannel plates. We also present the modulation transfer function (MTF) and noise power spectrum (NPS), again demonstrating significantly improved performance. For counting mode, we present the quantum efficiency (QE) as a function of incident electron energy. We have evaluated the charge collection efficiency (CCE) and we thereby demonstrate the presence of a ~200 nm thick dead layer that is linked with reduced CCE at low electron energies. Based on our findings, we believe that the MAPS technology is well matched to future XPEEM instruments using aberration correction.     

Noise characteristics of stacked CMOS active pixel sensor for charged particles

The noise characteristics of a stacked CMOS active pixel sensor (SCAPS) for incident charged particles have been analyzed under 4.5 keV Si⁺ ion irradiation. The source of SCAPS dark current was found to change from thermal to electron leakage with decreasing device temperature. Leakage current at charge integration part in a pixel has been reduced to 0.1 electrons s⁻¹ at 77 K. The incident ion signals are computed by subtracting reset frame values from each frame using a non-destructive readout operation. With increase of irradiated ions, the dominant noise source changed from read noise, and shot noise from the incident ions, to signal frame fixed-pattern noise from variations in sensitivity between pixels. Pixel read noise is equivalent to ten incident ions. The charge of an incident ion is converted to 1.5 electrons in the pixel capacitor. Shot noise corresponds to the statistical fluctuation of incident ions. Signal frame fixed-pattern noise is 0.7% of the signal. By comparing full well conditions to noise floor, a dynamic range of 80 dB is achieved. SCPAS is useful as a two-dimensional detector for microanalyses such as stigmatic secondary ion mass spectrometry.     

Development of smoothed particle hydrodynamics method for modeling active nematics

This article proposes a novel graphics processing unit-based active nematic flow solver based on the smoothed particle hydrodynamics (SPH) method. Nematohydrodynamics equations are discretized using the SPH algorithm. Flow behavior, nematic ordering, topological defects, and vorticity correlation are calculated and discussed in detail. The spectrum of the kinetic energy with respect to the wavenumber is calculated at high particle resolution, and its slope at the different length scales is discussed. To exploit the SPH capabilities, pathlines of nematic particles are evaluated during the simulation. Finally, the mixing behavior of the active nematics is calculated as well and described qualitatively. The effects of two important parameters, namely, activity and elastic constant are investigated. It is shown that the activity intensifies the chaotic mixing nature of the active nematics, while the elastic constant behaves oppositely.     

Effects of neutral particle beam on nano-crystalline silicon thin films, with application to thin film transistor backplane for flexible active matrix organic light emitting diodes

A novel deposition process for nano-crystalline silicon (nc-Si) thin films was developed using neutral beam assisted chemical vapor deposition (NBaCVD) technology for the application of the thin film transistor (TFT) backplane of flexible active matrix organic light emitting diode (AMOLED). During the formation of a nc-Si thin film, the energetic particles enhance nano-sized crystalline rather microcrystalline Si in thin films. Neutral Particle Beam (NPB) affects the crystallinity in two ways: (1) NPB energy enhances nano-crystallinity through kinetic energy transfer & chemical annealing, and (2) heavier NPB (such as Ar) induces damage & amorphization through energetic particle impinging. Nc-Si thin film properties effectively can be changed by the reflector bias. As increase of NPB energy limits growing the crystalline, the performance of TFT supports this NPB behavior. The results of nc-Si TFT by NBaCVD demonstrate the technical potentials of neutral beam based processes for achieving high stability and reduced leakage in TFT backplanes for AMOLEDs.     

基于粒子群算法的空间直线度误差评定

提出了一种满足最小区域法的空间直线度误差评价的新方法--粒子群算法。根据最小区域条件,建立了空间直线的数学模型以及优化目标函数。阐述了粒子群优化算法的原理和实现方法,然后根据粒子群算法优化求解。实例表明该方法对于空间直线度误差评定等非线性优化问题能得到最优解,可用于三坐标测量机等测量系统的空间直线度误差测量的数据处理。     

Important sensors for chiller fault detection and diagnosis (FDD) from the perspective of feature selection and machine learning

The benefits of applying automated fault detection and diagnosis (AFDD) to chillers include less expensive repairs, timely maintenance, and shorter downtimes. This study employs feature selection (FS) techniques, such as mutual-information-based filter and genetic-algorithm-based wrapper, to help search for the important sensors in data driven chiller FDD applications, so as to improve FDD performance while saving initial sensor cost. The ‘one-against-one’ multi-class support vector machine (SVM) is adopted as a FDD tool. The results show that the eight features/sensors, centered around the core refrigeration cycle and selected by the GA-SVM wrapper from the original 64 features, outperform the other three feature subsets by the GA-LDA (linear discriminant analysis) wrapper, with an overall classification correct rate (CR) as high as 99.53% for the 4000 test samples randomly covering the normal and seven typical faulty modes. The CRs for the four cases with FS are all higher than that without FS (97.45%) and the test time is much less, about 28-36%. The FDD performance for normal or each of the faulty modes is also evaluated in details in terms of hit rate (HR) and false alarm rate (FAR).     

Application of large area avalanche photodiodes for alpha liquid scintillation counting

In order to improve the resolution in alpha liquid scintillation and to promote this method for the measurement of actinides in environment, a silicon Large Area Avalanche Photodiode (LAAPD) has been tested as liquid scintillation detector. The set-up consists of a LAAPD (16 mm diameter) coupled to a thin vial containing alpha-emitters and a liquid scintillation cocktail. After optimization of several parameters like bias voltage, temperatures, counting geometry and composition of scintillating cocktail, energy resolutions are found to be better than those obtained with photomultiplier tubes: 5% (200 keV FWHM) for ²³²Th and 3.9% (260 keV FWHM) for ²¹⁶Po. The improvement in energy resolution is not due to higher quantum efficiency of the silicon device but to better uniformity of the spatial photoresponse. A few energy spectra of thorium, plutonium and americium are given as example.     

Properties of amorphous silicon thin films synthesized by reactive particle beam assisted chemical vapor deposition

Amorphous silicon thin films were formed by chemical vapor deposition of reactive particle beam assisted inductively coupled plasma type with various reflector bias voltages. During the deposition, the substrate was heated at 150 °C. The effects of reflector bias voltage on the physical and chemical properties of the films were systematically studied. X-ray diffraction and Raman spectroscopy results showed that the deposited films were amorphous and the films under higher reflector voltage had higher internal energy to be easily crystallized. The chemical state of amorphous silicon films was revealed as metallic bonding of Si atoms by using X-ray photoelectron spectroscopy. An increase in reflector voltage induced an increase of surface morphology of films and optical bandgap and a decrease of photoconductivity.     

尘埃粒子计数器的校准方法

尘埃粒子计数器主要用来评定洁净室洁净度等级、检测过滤器的过滤效率及洁净织物的发尘量等。尘埃粒子计数器的量值溯源因其特殊性,存在很大难度,多年来国内外都在致力于尘埃粒子计数器的校准研究。该文就研究以及编写的尘埃粒子计数器国家计量校准规范,来阐述尘埃粒子计数器的校准方法。     

Surrogates of plutonium for detection equipment testing

Fight against illicit trafficking of nuclear material relies on the possibility to detect nuclear material concealed in vehicles, people or cargo containers. This is done by equipping and training law enforcement and security staff in border stations or other points of access to strategic places and critical infrastructures with radiation detection equipment.The design, development, testing and evaluation of these instruments ideally require the use of real nuclear material to assess, verify and certify their detection performance. Availability of special nuclear material may be an issue, especially for industry, since only few specialized laboratories are licensed for such material.This paper tries to analyse and describe the possibility to use suitable surrogates that may replace the use of real nuclear material in testing the detection capabilities of instruments used in nuclear security.     

注射剂可见异物检测气泡干扰消除方法的研究

介绍了自动检测系统的构成,并提出了一种消除图像气泡干扰的方法.首先,采用图像差分方法消除原始图像中的大部分静态背景,然后对处理后的图像进行阈值分割、边缘检测、特征提取,重点研究了基于透光度、长宽比、紧凑度三个判据综合的气泡干扰消除方法.结果表明,该方法可以有效检测出医药注射剂中微小可见异物,检测正确率达到93%以上.     

Experimental and numerical modeling of particle levitation and movement behavior on traveling-wave electric curtain for particle removal

Traveling-wave electric curtain (EC) has been developed for potential application in particle removal/shield on solar panels and other surfaces. Levitation and transport of a particle in a traveling-wave electric field were simulated. Results show that levitation directions/angles and levitation trajectories differ because of the difference in starting positions and starting times. The particles in the two positive acceleration regions are levitated in opposite directions, and the particles distributed on the dielectric surface are levitated and transported successively rather than simultaneously. Movement trajectories are complex and affected by various factors. In the current paper, movement trajectories are modeled to analyze which motion modes are advantageous or disadvantageous to particle removal. This process is beneficial to elucidate the mechanism of particle removal and provide a guidance for movement control by designing appropriate operating parameters.     

微乳技术制备纳米微粒的研究进展

综述了微乳技术制备的纳米微粒的研究现状,并对微乳液的配备和实验中影响纳米微粒的主要因素进行了阐述,提出了其发展方向。     

Effects of main particle diameter on improving particle flowability for compressed packing fraction in a smaller particle admixing system

Particle flowability can be improved by admixing particles smaller than the original particles (main particles). However, the mechanisms by which this technique improves flowability are not yet fully understood. In this study, we examined compressed packing in a particle bed, which is affected by particle flowability. To estimate the mechanism of improvement, we investigated the effects of the main particle diameter on the improvement of compressed packing fractions experimentally.The main particles were 397 and 1460 nm in diameter and the admixed particles were 8, 21, 62, and 104 nm in diameter. The main and admixed particles were mixed in various mass ratios, and the compressed packing fractions of the mixtures were measured. SEM images were used to analyze the coverage diameter and the surface coverage ratio of the admixed particles on the main particles. The main particle packing fraction was improved as the diameter ratio (=main particles/admixed particles) increased. This was explained by a linked rigid-3-bodies model with leverage. Furthermore, the actual surface coverage ratio at which the most improved packing fraction was obtained decreased with increasing main particle diameter. This was explained by the difference in the curvature of the main particle surface.     

Multi-parameter regularization method for particle sizing of forward light scattering

The matrix equation in the inversion of particle sizing based on forward light scattering is an ill-posed problem. To solve such an inversion problem, a number of algorithms have been proposed. The single parameter regularization is effective for retrieving the particle size distribution, but the solution is usually oscillatory in the presence of measurement errors. In this work, a multi-parameter regularization is presented to diminish the oscillations of the solution, which is verified with simulations and experiments.     

直升机结构响应主动控制中传感器优选问题研究

针对直升机结构响应主动振动控制问题,本文提出了一种传感器优选方法,该方法能够在不减少待减振点数目的前提下,减少传感器数目并优化其位置,且保证系统全局减振效果基本不变,从而有效降低了整个控制系统的控制规模。优化过程采用遗传算法进行求解。以Z11直升机为例对该方法的有效性进行了验证。结果分析表明,利用该优选方法,能够得到传感器数目最少,且全局减振效果降低有限的传感器最优布置方案