Candidate for Residual Defect in Silicon Surface Barrier Detector

The residual defect in the pulse height defect of a silicon surface barrier detector is investigated theoretically. An application of the model of charge collection process leads to another candidate for the residual defect than the recombination defect. The residual defect is due to incomplete charge induction by electrons and holes inside a plasma column, which has dielectricity-like property. Quantity of induced charge is shown in a ratio to the number of produced electron-hole pairs as functions of depletion layer thickness, plasma column length and resistivity of the detector. Experimental result of the residual defect of ⁵⁸Ni ion and its analysis method applying this model are presented. The residual defect is successfully explained by this model.     

Longitudinal Drift and Fine dE/dx Sampling in Various Gas Mixtures

Results of measurements realized at 15 GeV/c in a tagged e/?/p beam are presented. A longitudinal drift detector of 88 cm total length consisting of 16 stages of 4.7 cm drift each was used. Fast shaped signals from the detector were processed in a set of Flash ADC's with 25 ns sampling interval, corresponding to 0.3 - 2.6 mm distance in the drift space. Resolution and particle separation efficiency obtained in mixtures of Ne + 10% C3H8, Ar + 5% C3H8, Ar + 20% CO2, C3H8 + 20% C2H6 and in pure CH4 are compared to the performance of a classical method of charge integration over large samples.     

Medium-energy heavy-ion single-event-burnout imaging of powerMOSFETs

We present the first experimental determination of the SEB sensitive area in a power MOSFET irradiated with a high-LET heavy-ion microbeam. We used a spectroscopy technique to perform coincident measurements of the charge collected in both source and drain junctions together, with a nondestructive technique (current limitation). The resulting charge collection images are related to the physical structure of the individual cells. These experimental data reveal the complex 3-dimensional behavior of a real structure, which can not easily be simulated using available tools. As the drain voltage is increased, the onset of burnout is reached, characterized by a sudden change in the charge collection image. “Hot spots” are observed where the collected charge reaches its maximum value. Those spots, due to burnout triggering events, correspond to areas where the silicon is degraded through thermal effects along a single ion track. This direct observation of SEB sensitive areas as applications for, either device hardening, by modifying doping profiles or layout of the cells, or for code calibration and device simulation     

Transient Response of Surface Barrier Detectors as a Function of Fission Fragment Energy

The transient response of silicon surface barrier detectors to fission fragments of Cf252 was observed over a range of incident fragment energies from 13.6 to 90 MeV. From these observations the effect of the plasma formed by the incident particle on the charge collection time was determined. The time to disperse the plasma, tp, was calculated as a function of incident particle energy, Eo, and applied field, E. It was found that tp ? Eo1/m where 2 ? m ? 3 and tp ? E-1. A simple model gave reasonable agreement with the experiments and indicated that the plasma is dispersed by field-enhanced diffusion.     

Dependence of plasma structure and propagation on microwave amplitude and frequency during breakdown of atmospheric pressure air

The structure and propagation of the plasma in air breakdown driven by high-power microwave have attracted great interest. This paper focuses on the microwave amplitude and frequency dependence of plasma formation at atmospheric pressure using one two-dimensional model,which is based on Maxwell's equations coupled with plasma fluid equations. In this model, we adopt the effective electron diffusion coefficient, which can describe well the change from free diffusion in a plasma front to ambipolar diffusion in the bulk plasma. The filamentary plasma arrays observed in experiments are well reproduced in the simulations. The density and propagation speed of the plasma from the simulations are also close to the corresponding experimental data. The size of plasma filament parallel to the electric field decreases with increasing frequency, and it increases with the electric field amplitude. The distance between adjacent plasma filaments is close to one-quarter wavelength under different frequencies and amplitudes. The plasma propagation speed shows little change with the frequency, and it increases with the amplitude. The variations of plasma structure and propagation with the amplitude and frequency are due to the change in the distribution of the electric field.     

Ionization of SiO2 by Heavy Charged Particles

Highly ionizing heavy charged particles generate significant charge as they pass through the thin thermally grown gate oxide of a MOSFET device. The amount of charge created by an alpha particle and proton is calculated and the yield of charqes which escape initial recombination is measured. The experimental results are shown to agree with a charge recombination model where an ionization track radius of 30-40 ? is assumed. Finally, implications of the findings for single charged particle effects in submicron dimension devices are discussed.     

过渡金属氧化物LaFe1-xCrxO3体系的晶体结构和光电子能谱研究

我们在端点化合物LaFeO3中掺入Cr^3 ，制备了LaFe1-xCrxO3体系的系列样品。经XRD分析证明所制备的样品为单相体系，用MarqX程序对XRD数据进行分析得到其晶格常数。分别测定了入射光子能量在Fe2p吸收边以下和以上的O1s芯能级谱。从电子结构角度探讨了该体系晶体结构变化趋势。初步得出结论：随着Cr^3 掺杂量在LaFe1-xCrxO3中的增加，O2p向Cr 3d的电荷转移量也发生有规律的变化。     

聚束系统设计与计算程序

LMOVE程序是一个模拟粒子纵向运动的FORTRAN语言程序。它可以计算由三电极双间隙聚束器(或这种聚束器的组合)、单狭缝谐波聚束器、静电加速管和自由飘浮空间组成的束流脉冲化系统。程序采用大量粒子模拟束团在纵向相空间内的运动,并用Monte-Carlo方法随机产生相空间内各代表点的初始条件。因此,较为适合模拟粒子在配有聚束器件的静电加速器中的纵向运动。本程序不考虑粒子的空间电荷效应。     

Gas pressure effect on plasma transport in a magnetic-filtered radio-frequency plasma source

Volume negative ion production relies on a magnetic filter(MF), where the plasma downstream of the MF is characterized by a strip-like pattern that consists of a bright and dense plasma region. In this work, we study, in a radio-frequency plasma source, the effects of operating pressure on this strip. This investigation, conducted using a Langmuir probe, shows that the plasma uniformity might be controlled through the gas pressure. Moreover, the operating pressure determines on which hemi-cylinder(side of magnetic field lines) the strip forms. This side inversion of the high-density plasma hemi-cylinder is due to an inversion of an ambipolar electric field that changes the E?×?B drift direction.     

Buried Channel Charge Transfer Device (CTD) Transient Radiation Hardening Using N-P-N Structures

Buried channel CTD's must be designed to isolate their depleted channels from charge generated in the substrate by penetrating radiation to obtain optimum transient radiation hardness or radiation detector time response. This can be achieved by employing an NPN structure so that the electrons generated in the N substrate are confined by the reverse biased P-N junction from diffusing across the P layer to the N channel. Unfortunately, moderate doped P layers often do not have the necessary conductivity required experimentally to pin the junction bias during intense transient radiation. However, the use of P+ layers is shown to accomplish this purpose. Although buried channel CTD's are used as experimental examples, the principles are applicable to a wide range of MOS charge storage devices. One potential application is in the reduction of alpha particle induced soft errors associated with conventional packaging. This soft error problem is a significant issue in future small cell VLSI development.     

Characterization of Cable Gun Plasma with a Charge Collector Array

The density,drift velocity and reproducibility of the plasma produced by a cable plasma gun array have been measured with a charge collector array,The plasma is used to prefill a coaxial plasma-opening switch with a conducting time approaching 0.4us,The reproducibility of the plasma source in subsequent shots is better than 5%.Near the gun nozzle and the opposite electrode,the plasma density amounts to 10^15cm%-3,which is 2 times to 3 times that in the gap between the two coaxial electrodes.A plasma drift velocity of about 2.4cm/μs is observed from the time of flight of the charged particles.Both plasma density and drift velocity increase almost linearly with the rise in charge voltage.     

Radiation-Induced Charge Transport and Charge Buildup in SiO2 Films at Low Temperatures

Studies of the temporal, temperature, and electricfield dependences of radiation-induced charge transport have been performed for radiation-hardened SiO2 films. At room temperature for high applied fields, nearly all electrons and holes generated in the oxide by a pulse of ionizing radiation (5-keV electrons) drift to the interfaces, whereas at low temperatures only electrons contribute to observed transport for relatively low fields. Below ~130°K at high fields, field-induced emission of trapped holes occurs, giving rise to collection within seconds of a significant fraction of the total number of holes generated. The present hole transport data are accounted for quite well in terms of a multiple-trapping model with a spread in trap levels ranging from ~0.3 to ~0.5 eV from the valence band. Comparison with the stochastic hopping transport model is made and that model is found to be less satisfactory in explaining these data. Charge buildup was examined in a Co60 environment and it is demonstrated that oxides exhibiting radiation tolerance at room temperature display severe radiation-induced changes at 77°K. It is also demonstrated that low-temperature charge buildup problems can be alleviated either by employing an ion-implanted oxide or by applying a relatively high field to the oxide during irradiation.     

Spectrum-Averaged One-Group Cross Sections of Actinides Based on JENDL-3

When uranium vapor is generated with an electron beam evaporator, a uranium plasma is formed on the evaporating surface. This plasma rises and expands with the vapor. Propagation behavior of this plasma was investigated by measuring plasma parameters, drift energy of ions and vapor flux along the propagation path. Over the range of 20-50 cm from the evaporation surface, the plasma density decreased from 3 × 10⁹ cm^?3 to 3 × 10⁸ cm^?3, while the electron temperature had a constant value of 0.29 eV. When the space potential was lowered from 1.48 to 0.80 V, the plasma ions were accelerated to increase the drift energy from 1.50 to 2.14 eV. Validity of the Boltzmann electron distribution was checked by comparing the space potential distribution with the plasma density distribution, and also the floating potential distribution with the ion flux distribution. These results confirm that the ambipolar diffusion governs the plasma propagation behavior. The change in the plasma density during its propagation occurred not only by an increase of plasma volume, but by the ion acceleration toward the propagation direction as well.     

Signal charge sharing in multilinear drift detectors: design andexperimental characterization

Multilinear silicon drift detectors (MLSDDs) are radiation detectors which combine excellent energy and position resolution with high count-rate capabilities. This is achieved by controlling the diffusion of the signal charges and limiting their lateral spread during the drift. This paper will present a study of the signal electrons' transport in MLSDDs in comparison with the experimental measurements. Three-dimensional simulations were carried out, taking into account diffusion effects and mutual electrostatic interaction between the signal electrons. A representative sample of these simulations will be presented. Signal sharing in a multilinear drift detector and in a “classical” multi-anode drift detector are characterized and discussed. The results are useful to tailor the design of MLSDDs for the detection of different kinds of radiation (e.g., optical photon, X-ray, ionizing particle) and to optimize signal charge sharing and detector performance according to a particular application purpose     

Neutron-induced radiation damage in silicon detectors

Ion-implanted silicon pad detectors fabricated on different n-type and p-type silicon wafers with initial resistivities between 2.6 and 12.9 kΩcm were irradiated with neutrons of ~1 MeV energy, up to a fluence of 5×10¹³ n cm^-2. The evolution of diode leakage current and capacitance characteristics is presented as a function of the neutron fluence. The reverse diode current increases proportionally to the neutron fluence. There is evidence that the doping of the initial n-type material evolves towards intrinsic and inverts to an apparent p-type at fluences between 1×10¹³ and 3×10¹³ n cm^-2, depending on the initial silicon resistivity. There is also evidence that p-type material remains of the same conduction type with a slight increase of the acceptor doping with fluence. The signal shape and the charge collection efficiency for incident β particles were measured     

Modelling effect of magnetic field on material removal in dry electrical discharge machining

One of the reasons for increased material removal rate in magnetic field assisted dry electrical discharge machining(EDM) is confinement of plasma due to Lorentz forces.This paper presents a mathematical model to evaluate the effect of external magnetic field on crater depth and diameter in single-and multiple-discharge EDM process.The model incorporates three main effects of the magnetic field,which include plasma confinement,mean free path reduction and pulsating magnetic field effects.Upon the application of an external magnetic field,Lorentz forces that are developed across the plasma column confine the plasma column.Also,the magnetic field reduces the mean free path of electrons due to an increase in the plasma pressure and cycloidal path taken by the electrons between the electrodes.As the mean free path of electrons reduces,more ionization occurs in plasma column and eventually an increase in the current density at the inter-electrode gap occurs.The model results for crater depth and its diameter in single discharge dry EDM process show an error of 9%-10%over the respective experimental values.     

Cryogenic investigations and modelling of inter-defect charge exchange in silicon particle detectors

Silicon detectors in particle physics experiments at the CERN Large Hadron Collider (LHC) will be exposed to high levels of damaging radiation. The resulting changes in detector doping concentration (N_eff) have been identified as the principal obstacle to long-term operation in the LHC environment. We have previously proposed a model whereby the transfer of charge between closely spaced defects in the terminal clusters formed during heavy particle irradiation is responsible for a significant fraction of these changes in N_eff. The defects involved, the divacancy (V₂) and two unidentified intrinsic defects known as E70 and E170, are postulated to exchange charge via a manifestly non-Shockley–Read–Hall mechanism. Although the model has been remarkably successful in describing experimental measurements at room temperature, direct observations of the charge exchange process have not been forthcoming, not least because of the complexity of the spectroscopic techniques required. We present a comparison between cryogenic measurements of N_eff and the predictions of the model in order to test further the validity of our work to date.     

A review of ion beam induced charge microscopy

Since its development in the early 1990’s, ion beam induced charge (IBIC) microscopy has found widespread applications in many microprobe laboratories for the analysis of microelectronic devices, dislocations, semiconductor radiation detectors, semi-insulating materials, high power transistors, charge-coupled arrays, solar cells, light emitting diodes, and in conjunction with Single Event Upset imaging. Several modalities of the techniques have been developed, such as lateral IBIC and time-resolved IBIC. The theoretical model of IBIC generation and collection has developed from a one-dimensional model of charge drift and diffusion to a detailed model of the motion of ion charge carriers in semiconductors and insulators. This paper reviews the current state-of-the-art of IBIC theory and applications.     

Time dependence of interface trap formation in MOSFETs followingpulsed irradiation

The time dependence of interference trap (N_it) formation in MOSFETs was studied as a function of gate oxide thickness, oxide growth type, substrate orientation, temperature, and gate bias. Two different N_it formation mechanisms are observed. Most (typically 90%) of the formation, called the late process, occurs slowly at long times (1-10000 s) after the radiation pulse. From a variety of experimental data, it is concluded that the rate of the late process is limited by drift of a radiation-induced positive ion, probably H⁺ , through the gate oxide to the Si-SiO₂ interface where the N_it are formed. A relatively fast, or early, process is responsible for a small percentage of the total N_it formation. The time constant for this process appears to be consistent with hole drift through the oxide     

p+~(107,109)Ag核反应数据的计算和分析

本工作通过理论计算的方法获得了一套适合入射能量为从阈值到200 MeV的p+107,109 Ag核反应全套微观数据。首先,使用光学模型理论进行调参计算,得到了一套适合入射能量为从阈值到340MeV的p+107,109 Ag核反应Becchetti-Greenlees光学势参数,这套参数与实验数据符合很好。其次,在这套光学势参数的基础上用扭曲波玻恩近似对入射能量从阈值到200MeV的p+107,109 Ag直接非弹性散射截面进行了计算。最后,使用核反应统计理论计算了入射能量从阈值到200MeV的p+107,109 Ag核反应各反应道的截面和出射粒子能谱,得到了该能区p+107,109 Ag核反应全套微观数据。将所有计算值与实验数据进行比较,结果表明,所得到的全套微观数据与实验数据符合很好。