A high-resolution, two-dimensional, electron imaging integrated circuit

A theoretical and experimental study is report-ed of the gain of microchannel plate (MCP) electron multipliers under conditions of output charge satur-ation. Theoretical calculations, assuming a wall charge saturation mechanism, are used to interpret peak gain and pulse height distribution FWHM data obtained with a number of chevron MCP multipliers. A curved surface MCP intended for use with grazing incidence X-ray optics is described. The effects of an inter-plate voltage are described. Limiting pulse height FWHMs around 30% have been obtained. The properties of straight channel chevrons and single curved channel MCPs are briefly compared.

Atomic layer deposition (ALD) technology is used to nanoengineer functional films inside the pores of microchannel plate (MCP) electron multipliers, enabling a novel MCP manufacturing technology that substantially improves performance and opens novel applications. The authors have developed custom tools and recipes for the growth of conformal films, with optimized conductance and secondary electron emission inside very long channels (∼6–20 μm diameter and >600 μm length, with tens of millions of channels per single MCP) by ALD. The unique ability to tune the characteristics of these ALD films enables their optimization to applications where time-resolved single particle imaging can be performed in extreme conditions, such as high counting rates at cryogenic temperatures. Adhesion of the conductive and emissive nanofilms to the 20 μm pore MCP glass substrates and their mechanical stability over a very wide range of temperatures (10–700 K) were confirmed experimentally. Resistance of ALD MCPs was reproducible during multiple cool-down cycles with no film degradation observed. Optimizing resistance of novel MCPs for operation at cryogenic temperature should enable high count rate event detection at temperatures below 20 K.

A cold electron source has been developed using a microchannel plate (MCP) electron multiplier. Primary electron emission is initiated by illumination with ultraviolet photons from a diode. Final electron emission currents of up to 10 μA in continuous wave (CW) mode and 10 mA in pulsed mode have been achieved from a MCP with an active diameter of 5.5 mm. Electron emission generated by UV photons with a wavelength of 260 nm has been shown to be about 30 times more efficient than emission generated by photons with a wavelength of 300 nm. Application of this cold electron source in mass spectrometry is discussed.

In this article, the Micro-Channel Plate Electron Multiplier is studied to carry out the microcurrent multiplication process in order to solve the short lifetime problem of the Electron Multiplier of the present Cesium Clock. Based on the current parameters of the Micro Channel Plate Electron Multiplier, the gain is enhanced by selecting the structure parameters and the application of the cascade structure, the noise is reduced by the improvement of the structure and handing procedure, the lifetime is enhanced by optimization of the working parameters, thus a high gain, low noise, and long lifetime Micro-Channel Plate Electron Multiplier is obtained, which could improve the performance of the Cesium Clock for the navigation system.

Microchannel plate is widely used in the field of low light level night vision, photomultiplier, tubes, X-ray enhancer and so on. In order to meet the requirement of microchannel plate electron multiplier, we used the method of thermal oxidation to produce a thin film of silicon dioxide which could play a role in electric insulation. Silicon dioxide film has a high breakdown voltage, it can satisfy the high breakdown voltage requirements of electron multiplier. We should find the reasonable parameter values and preparation process in the oxidation so that the thickness and uniformity of the silicon dioxide layer would meet requirement. This article has been focused on researching and analyzing of the problem of oxide insulation and thermal stress in the process of production of silicon dioxide film. In this experiment, dry oxygen and wet oxygen were carried out respectively for 8 hours. The thickness of dry oxygen silicon dioxide films was 458 nm and wet oxygen silicon dioxide films was 1.4 μm. Under these conditions, the silicon microchannel is uniformity and neat, meanwhile the insulating layer's breakdown voltage was measured at 450 V after the wet oxygen oxidation. By using ANSYS finite element software, we analyze the thermal stress, which came from the microchannel oxygen processes, under the conditions of which ambient temperature was 27 ℃ and porosity was 64%, we simulated the thermal stress in the temperature of 1200 ℃ and 1000 ℃, finally we got the maximum equivalent thermal stress of 472 MPa and 403 MPa respectively. The higher thermal stress area was spread over Si-SiO₂ interface, by simulate conditions 50% porosity silicon microchannel sample was selected for simulation analysis at 1100 ℃, we got the maximum equivalent thermal stress of 472 MPa, Thermal stress is the minimum value of 410 MPa.

We describe the synthesis, characterization, and application of nanocomposite, tunable resistance coatings consisting of conducting, metallic nanoparticles embedded in an amorphous dielectric matrix. These films are comprised of M:Al2O3 with M=Mo or W, and are prepared by atomic layer deposition (ALD) using alternating exposures to trimethyl aluminum and H2O for the Al2O3 ALD and alternating MF6/Si2H6 exposures for the metal ALD. By varying the ratio of ALD cycles for the metal and the Al2O3 components in the film, we can tune precisely the resistance of these coatings over a very broad range from 105-1012 Ohm.cm. These films exhibit ohmic behavior and resist breakdown even at high electric fields of 107 V/m. Moreover, the self-limiting nature of ALD allows us to grow these films inside of porous substrates and on complex 3D surfaces. As a result of these qualities, our nanocomposite films have proved exceptional as resistive coatings in microchannel plate electron multipliers and as charge drain coatings in electron-optical devices.

A CMOS time-of-flight (TOF) system-on-a-chip (SoC) for precise time-interval measurement with low power and high rate has been developed. Microchannel plate electron multipliers or photomultiplier tubes (PMTs) typically produce the start-stop delta-Ts of radiation events to be processed. The TOF chip includes two constant fraction discriminators (CFDs) and a time-to-digital converter (TDC). The CFDs interface to start and stop anodes through two simple preamplifiers and perform the signal processing for time walk compensation. The TDC digitizes the time difference with reference to an off-chip precise oscillator. The design is full custom in both the analog and the digital sections. A first version of the TOF chip developed in a 0.8-/spl mu/m CMOS process achieved CFD time walk of /spl sim/350 ps for an input amplitude dynamic range of 40 dB and a combined CFD+TDC time jitter of /spl sim/180 ps. The total power dissipation was /spl sim/20 mW at an event rate of 100 K/s and /spl sim/30 mW at a rate of 1 Meg/s. This chip is part of the high-energy neutral atom instrument onboard the NASA/IMAGE spacecraft launched in March 2000. It is selected for many other instruments, including the particle sensor, the fast plasma sensor, and the laser altimeter of Messenger for the Mercury exploration to be launched in 2004.

The multiplication process in open-type continuous-dynode electron multipliers (channel electron multipliers, microchannel plates) is considered as a Markov process that is continuous in time (channel length) and discrete in space (number of electrons in the channel). As a result of this consideration, the relationships for the mean gain and the probability distributions of the number of electrons at the channel output in the saturated and nonsaturated operating modes were obtained. The relationships are in good agreement with the measured dependences of the gain on the power-supply voltage and the distributions of the number of electrons at the channel output.

Photocatalytic and photochemical processes of AgCl/TiO ₂ studied with a fully integrated X‐ray photoelectron spectrometer

Vacuum based devices, such as Photo Multiplier Tubes (PMT) and Micro Channel Plates (MCP), have been for many years the sensors of choice for most applications calling for photon counting and timing (Renker, 2004). While providing very good sensitivity, noise and timing characteristics, these photodetectors feature a number of disadvantages: they are bulky, fragile, and sensitive to magnetic fields; they require very high operation voltages, and have large power consumption; in their high-performance models, providing good spatial resolution, they are still very expensive. For high-sensitivity imaging applications, suitable solutions are represented by CCD cameras coupled with either MCP Image Intensifiers (I-CCDs) or Electron Multipliers (EM-CCDs) (Dussault & Hoess, 2004). However, besides being very expensive, their performance is not completely satisfactory in extreme time resolved measurements. For reasons of cost, miniaturization, ruggedness, reliability, design flexibility, integration density, and signal processing capabilities, a fully solid-state solution (and, particularly, CMOS technology) would be highly desirable. Among the advanced CMOS image sensors so far reported, the most promising ones in terms of high sensitivity and fast timing are those based on Single Photon Avalanche Diodes (SPADs). SPADs are avalanche photodiodes operated in the so-called Geiger mode, i.e., biased above breakdown, so as to be sensitive to single photons (Cova et al., 1996). Although these sensors have been developed for more than 30 years, in particular owing to the group of Prof. Cova at Politecnico di Milano, and single devices have reached outstanding performance (Ghioni et al., 2007), only recently the perspective of making a SPAD-based camera has become feasible. The first SPAD-based pixel arrays in CMOS technology have been demonstrated only a few years ago (Rochas et al., 2003a), but since then further developments rapidly followed, also facilitated by the availability of commercial, High-Voltage CMOS technologies (HV-CMOS) aimed at integrated circuits for power electronics, as well as of specially tailored “imaging” processes, which have been boosted by the huge market of

Li-ion batteries are used widely for portable energy storages because of large capacity. Generally, the carbonate-based organic solvents are used as the electrolytes. Most of these organic solvents decompose during the first charge, resulting in formation of the solid electrolyte interphase (SEI) film, which plays an important role for Li-ion batteries on the active materials. Although there are many reports about the SEI film, its nature and function have not been clarified yet. We have already reported that lithium phosphorous oxynitride (LiPON) film acts as an artificial SEI film in 1-butyl-1-methylpyrrolidinium (BMP+) and 1-ethyl-3-methylimidazolium (EMI+) bis(trifluoromethylsulfonyl)amide (TFSA–) ionic liquids containing LiTFSA, and LiTFSA-glyme solvate ionic liquid. [1,2] Ionic liquids are expected to be the alternative electrolytes for Li-ion batteries, since ionic liquids have low flammability and low volatility, which are expected to improve safety of the batteries. However, the SEI film formed by the decomposition of ionic liquids is not preferable for deposition and dissolution of lithium. In this study, deposition and dissolution of lithium through a Li2CO3 thin film prepared by RF magnetron sputtering were investigated in BMPTFSA containing LiTFSA. The Li2CO3 thin film was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractrometer, and X-ray photoelectron spectrometer (XPS). All the electrochemical measurements were performed using an airtight three-electrode cell. The Ni electrode with or without the Li2CO3 thin film was used as a working electrode. Li foil was used as a reference and counter electrode. After electrochemical measurements, the electrode was washed with dimethyl carbonate (DMC) and characterized by SEM and XPS. SEM observation and XPS measurement showed that the Ni substrate was covered with the Li2CO3 thin film completely. The Li2CO3 thin film on the substrate was X-ray amorphous. However, the crystalline domains were observed sparsely by TEM observation. The deposition and dissolution of lithium were possible through the Li2CO3 thin film in BMPTFSA containing 1 M LiTFSA. Although the cathodic current attributed to the decomposition of the electrolytes was observed on the Ni electrode, it was suppressed on the Ni electrode with the Li2CO3 thin film. These results indicate that the Li2CO3 thin film has the possibility to act as an artificial SEI film. The depth analysis by XPS revealed that lithium deposited between the Li2CO3 thin film and Ni electrode. From AC impedance measurement, the ionic conductivity of the Li2CO3 thin film was estimated to be 1.3 × 10−8 S cm−1.

Output Energy Distribution of a Microchannel Plate

The microchannel plate (MCP) is a semiconducting glass plate containing an array of open channels that can provide photo-electron amplification for imaging applications. Conventional MCP channel geometries are designed to inhibit ion-feedback that occurs in straight channel plates at high applied potentials. Ion-feedback must be reduced as much as possible since its presence degrades the performance of the plate by adding noise to the plate's output. The performance characteristics of a new geometrical design for a high-gain MCP, that employs channels that spiral downward in a helical fashion to inhibit ion-feedback, have been evaluated in the laboratory. A Multi-Anode Microchannel Array (MAMA) detector was used to test the new MCP. The "helical-channel" MCPs tested to date have channel diameters of 50 microns and have demonstrated stable operation at gains above 106 electrons/pulse. The goal of the program is to develop "helical-channel" MCPs with channel diameters as small as 12 microns within two years. Detailed performance data including the dynamic range, pulse-height distribution, and gain characteristics of this new MCP will be presented.

Ultrafast photoelectron and photoion spectroscopy (as well as their combination known as "coincidence spectroscopy") utilizes detectors based on different electron multipliers such as microchannel plates or single-channel electron multipliers. These detectors have a few important limitations such as fast-signal distortion (low pass operation), mutually exclusive positive or negative mode, dead time, and requirement of trigger. A high-pass induction detector, based on a hollow-cored toroidal coil, was developed that overcomes the above-mentioned limitations. The frequency-dispersive response and linearity of different configurations were analyzed. It is shown that the response is enhanced for ultrafast electron signals, dependent on construction parameters, thus offering response flexibility by design. Kinetic energy distributions of pseudospark-induced electron pulses are characterized in order to validate the capabilities in real applications.

This chapter describes the development of the continuous-dynode electron multiplier and its evolution into the microchannel plate (MCP). The fabrication procedures for MCPs are described and the performance characteristics of MCPs and MCP stacks are enumerated. The configurations and performances of imaging MCP electronic readout systems currently in use in space instruments are described in detail. The unique capabilities of MCP electronic systems for fast timing and for time-tag imaging are listed. Finally, the prospects for the development of the next generation of MCPs are briefly outlined.