Articoli di riviste: "Emissive cathode"

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Chaharsoughi, Mina Shiran, Mohammad Jafar Hadianfard e Mohammad Mahdi Shiezadeh. "Study the Effect of Nanoemissive Materials on M-Type Cathode Performance". Advanced Materials Research 829 (novembre 2013): 772–77. http://dx.doi.org/10.4028/www.scientific.net/amr.829.772.

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In this study, the stoichiometric mixture of barium carbonate, calcium carbonate, and aluminum oxide with ratio of 5:3:2 was produced by two individual methods: sol-gel combustion and ball-milling method used as a precursor of electron emissive material on impregnated cathodes which make up high power vacuum microwave tubes such as klystrons. Results from X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy on emissive material produced by sol-gel combustion technique show that its crystallite size is under 45 nm, and particle size is less than 100 nm, and the chemical composition of emissive material is uniform at nanoscale. The effects of two types of emissive materials on operation properties of M type cathode were also investigated. The two types of manufactured M cathodes were tested inside an electron gun under maximum anode voltage 10.5 kV in continues wave mode, at 1100 ͦC, and the anode-cathode distance was fixed at 5 mm. results show that the emission current of M cathode impregnated by nano emissive materials is more uniform than conventional cathode, and its current density is about 2.7 A/cm2, while in I-V curve it does not reach at saturated-emission region at 10.5 kV.

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Stępińska, Izabela, Elżbieta Czerwosz, Mirosław Kozłowski, Halina Wronka e Piotr Dłużewski. "Studies of field emission process influence on changes in CNT films with different CNT superficial density". Materials Science-Poland 36, n. 1 (18 maggio 2018): 27–33. http://dx.doi.org/10.1515/msp-2018-0001.

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Abstract Field emission from materials at high electric fields can be associated with unfavorable or even destructive effect on the surface of the investigated cathode. The impact of high voltage electric power supply causes locally very strong electric fields focusing on the cathode surface. It causes a number of phenomena, which can adversely affect the morphology and the structure of the cathode material. Such a phenomenon is, for example, peeling of an emissive layer from the substrate or its burnout. It results in tearing of the layer and a decrease or loss of its ability to electrons emission. The cold cathodes in a form of CNT films with various CNTs superficial distribution are obtained by physical vapor deposition followed by chemical vapor deposition. CNTs are catalyzed in pyrolytic process with xylene (CVD), by Ni in a form of nanograins (few nm in size) placed in carbonaceous matrix. These films are built of emissive CNTs - carbonaceous film deposited on different substrates. In this work, the morphology and topography of superficial changes resulting from external electric field in such films were investigated.

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Isakova, Yulia I., Galina E. Kholodnaya e Alexander I. Pushkarev. "Influence of Cathode Diameter on the Operation of a Planar Diode with an Explosive Emission Cathode". Advances in High Energy Physics 2011 (2011): 1–14. http://dx.doi.org/10.1155/2011/649828.

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This paper presents the results of experimental investigations into the current-voltage characteristics of a planar diode with an explosive emission cathode made from graphite. Studies were performed using a TEU-500 pulsed electron accelerator (350–500 keV, 100 ns, 250 J per pulse). Duration of diode operation, in a mode when electron current is limited by the emissive ability of the graphite cathode, is 15–20 ns. The contribution of the cathode periphery to total electron current appears only as an increase in the emissive surface area due to an expansion of explosive plasma. Investigations of an ion diode with a graphite cathode (plane and focusing geometry) were also carried out. Experiments were performed using a TEMP-4M ion accelerator, which forms two nanosecond pulses: the first negative pulse (150–200 kV, 300–600 ns) followed by the second positive (250–300 kV, 150 ns). Total diode current in the first pulse is well described by the Child-Langmuir law for electron current at a constant rate of plasma expansion, equal to 1.3 cm/μs. It is shown that for an area of flat cathode over 25 cm2, the influence of edge contribution does not exceed measurement error of total diode electron current (10%).

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Chen, Jing, Qianqian Huang e Wei Lei. "Dual-Facets Emissive Quantum-Dot Light-Emitting Diode Based on AZO Electrode". Materials 15, n. 3 (19 gennaio 2022): 740. http://dx.doi.org/10.3390/ma15030740.

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We report on a green, dual emissive quantum-dot light-emitting diode (QLED) using alumina (Al)-doped ZnO (AZO) to adjust the band offset between the cathode and QD-emitting layers. The dual emissive QLED structure was designed by enhancing the efficient hole injection/transfer and slowing down the electron injection/transfer from AZO to the QD. The QLEDs presented a maximum luminance of 9450 cd/m2, corresponding to a power efficiency of 15.7 lm/W, a current efficiency of 25.5 cd/A, as well as a turn-on voltage of 2.3 V. It is worth noting that the performance of the dual emissive QLED is comparable to that of a single emissive QLED. Therefore, there is a 1.3-fold enhancement in the performance of the QLED based on the AZO cathode due to the balanced charge injection/transfer.

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Yang, Yang, Wen Zheng Yang, Wei Dong Tang e Chuan Dong Sun. "Temperature Dependent Study of Carrier Diffusion in Photon Enhanced Thermionic Emission Solar Converters". Advanced Materials Research 772 (settembre 2013): 634–39. http://dx.doi.org/10.4028/www.scientific.net/amr.772.634.

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Photon Enhanced Thermionic Emission (PETE) is a novel concept in solar energy conversion, which can efficiently harvest solar energy at elevated temperatures. However, the temperature dependence of material parameters has not been clearly stated so far. In this study, a model for carrier transport is presented based on one dimension diffusion equation. Material data of GaAs are used to testify the temperature impact on material parameters. We find that for higher doped p-type GaAs which is suitable for PETE cathode material, its electron diffusion length shows weak temperature dependence. Carrier transport efficiency can be boosted by optimizing the geometry of the cathode and the optical parameters of the material. Finally, we propose a design of reflective mode cathode with reflective back surface and nanostructure emissive surface for PETE application.

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Nouzman, L., e G. L. Frey. "Directed migration of additives to form top interlayers in polymer light emitting diodes". Journal of Materials Chemistry C 5, n. 48 (2017): 12744–51. http://dx.doi.org/10.1039/c7tc04586g.

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Sibbett, W., S. C. Douglas, M. I. Harbour, B. A. Kerr, S. N. Spark e Y. M. Saveliev. "Effect of cathode end caps and a cathode emissive surface on relativistic magnetron operation". IEEE Transactions on Plasma Science 28, n. 3 (giugno 2000): 478–84. http://dx.doi.org/10.1109/27.887651.

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Becatti, G., F. Burgalassi, F. Paganucci, M. Zuin e D. M. Goebel. "Resistive MHD modes in hollow cathodes external plasma". Plasma Sources Science and Technology 31, n. 1 (1 gennaio 2022): 015016. http://dx.doi.org/10.1088/1361-6595/ac43c4.

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Abstract A significant number of plasma instabilities occur in the region just outside of hollow cathodes, depending on the injected gas flow, the current level and the application of an external magnetic field. In particular, the presence of an axial magnetic field induces a helical mode, affecting all the plasma parameters and the total current transported by the plasma. To explore the onset and behavior of this helical mode, the fluctuations in the plasma parameters in the current-carrying plume outside of a hollow cathode discharge have been investigated. The hollow cathode was operated at a current of 25 A, and at variable levels of propellant flow rate and applied magnetic fields. Electromagnetic probes were used to measure the electromagnetic fluctuations, and correlation analysis between each of the probe signals provided spatial-temporal characterization of the generated waves. Time-averaged plasma parameters, such as plasma potential and ion energy distribution function, were also collected in the near-cathode plume region by means of scanning emissive probe and retarding potential analyzer. The results show that the helical mode exists in the cathode plume at sufficiently high applied magnetic field, and is characterized by the presence of a finite electromagnetic component in the axial direction, detectable at discharge currents ⩾25 A. A theoretical analysis of this mode reveals that one possible explanation is consistent with the hypotheses of resistive magnetohydrodynamics, which predicts the presence of helical modes in the forms of resistive kink. The analysis has been carried out by linear perturbation of the resistive MHD equations, from which it is possible to obtain the dispersion relation of the mode and find the k–ω unstable branch associated with the instability. These findings provided the basis for more detailed investigation of resistive MHD modes and their effect in the plume of hollow cathodes developed for electric propulsion application.

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Yokoo, Kuniyoshi. "Experiments of highly emissive metal–oxide–semiconductor electron tunneling cathode". Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures 14, n. 3 (maggio 1996): 2096. http://dx.doi.org/10.1116/1.588878.

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Hartmann, W., G. Kirkman, V. Dominic e M. A. Gundersen. "A super-emissive self-heated cathode for high-power applications". IEEE Transactions on Electron Devices 36, n. 4 (aprile 1989): 825–26. http://dx.doi.org/10.1109/16.22493.

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Grigoriev, Sergey, Alexander Metel, Marina Volosova e Yury Melnik. "Improvement of Thin Film Adhesion Due to Bombardment by Fast Argon Atoms". Coatings 8, n. 9 (28 agosto 2018): 303. http://dx.doi.org/10.3390/coatings8090303.

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A new hollow cathode sputtering system is used for beam-assisted deposition of thin films on dielectric substrates. A copper target placed at the hollow cathode bottom is uniformly sputtered by argon ions from the glow discharge plasma filling the cathode. Through an emissive grid, sputtered copper atoms leave the cathode together with accelerated argon ions. On their way to the substrate, the ions—due to charge exchange collisions—turn into fast argon atoms bombarding the growing film. With increasing argon ion energy, continuous bombardment results in the film adhesion improvement and reduction of the deposition rate down to zero, at an energy of about 2 keV. The pulsed bombardment does not influence the film deposition rate, and results in a monotonic growth of the film adhesion up to 20 MPa when increasing the fast atom energy up to 10 keV.

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Jenkins, S. N., D. K. Barber, M. J. Whiting e M. A. Baker. "Preliminary results on the chemical characterisation of the cathode nickel—emissive layer interface in oxide cathodes". Applied Surface Science 215, n. 1-4 (giugno 2003): 78–86. http://dx.doi.org/10.1016/s0169-4332(03)00278-2.

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13

Zemskov, Yu A., Yu I. Mamontov, I. V. Uimanov, N. M. Zubarev, A. V. Kaziev, M. M. Kharkov e S. A. Barengolts. "Instabilities of electrical properties of He-induced W “fuzz” within the pre-breakdown and breakdown regimes". Journal of Physics: Conference Series 2064, n. 1 (1 novembre 2021): 012004. http://dx.doi.org/10.1088/1742-6596/2064/1/012004.

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Abstract The investigation of the He-induced W “fuzz” electrical properties was carried out. For the research, an automated experimental setup was designed. The setup was based on a vacuum chamber operated under high vacuum conditions (~ 10−7 Pa). The vacuum diode under investigation comprised of a flat W “fuzz” cathode with an area of about 1 cm2 and a 2 mm radius cylindrical copper anode with a hemisphere tip. The cathode-anode distance was about 100 μm. The voltage applied was up to 10 kV. A DAC/ADC module controlled an HV power supply and automatically registered currents and voltages in the circuit. The effect of a spontaneous change in the emissive ability of the investigated surface area was observed. These changes can vary significantly in magnitude. Large-scale changes can lead to a permanent increase in the emissive ability of a specific area or to a breakdown of the gap. Small changes, as a rule, are reversible, have a stepped nature, and make it difficult to record and interpret the current-voltage characteristics of the field emitter.

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Sirijarutus, Wattanaruk, Sittan Charoensuwan, Pawonwan Thanakit, Sirapat Pratontep e Darinee Sae-Tang Phromyothin. "A Study and Characterization of Photophysical Properties of Fluorene Derivative Thin Film". Key Engineering Materials 675-676 (gennaio 2016): 201–4. http://dx.doi.org/10.4028/www.scientific.net/kem.675-676.201.

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An emissive layer, fluorene derivative, was performed for organic light-emitting device properties. The preparation of fluorene derivative thin film by spin coating and convective technique was studied the band diagram of thin films which its properties out as the energy gap (Eg). UV-Visible spectrophotometer has been used to investigate the thin film properties. The results indicates spectacular property which occurs the optical properties, fluorescence in thin film and luminescence as a green light in device that it could be applied as emissive layer for organic light-emitting diodes (OLEDs) since the appropriate work function with cathode and anode, aluminum metal and indium tin oxide layer (ITO), respectively.

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Li, Jing-Ju, e J. X. Ma. "Sheath near a negatively biased electron-emitting wall in an ion-beam-plasma system and its implication to experimental measurement". Physics of Plasmas 30, n. 1 (gennaio 2023): 013510. http://dx.doi.org/10.1063/5.0126650.

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In the previous experiment by Li et al., [Phys. Plasmas 19, 113511 (2012)], a deep virtual cathode was measured within an ion sheath near a negatively biased stainless steel plate immersed in an ion-beam-plasma system. The appearance of a virtual cathode was attributed to secondary electrons produced by the high speed ion beam instead of the plasma electrons since these electrons are depleted in the sheath. This paper presents a theoretical model of the sheath structure in the ion-beam-plasma system near an electron-emitting wall. The results show that the presence of the ion beam will compress the whole sheath and make it more difficult to form the virtual cathode, i.e., it causes the increase in the threshold density of the emitted electrons at the wall needed to form the virtual cathode. When comparing with the previous experimental results, it is found that the needed secondary electron yield is unrealistically high in order to obtain the experimentally measured depth of the virtual cathode. Possible experimental uncertainties are discussed concerning the use of an emissive probe when it is too close to the wall.

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YANG, KI-SUNG, HO-SIK LEE, SEUNG-UN KIM, YOON-KI JANG, DOO-SEOK KIM, HOON-KYU SHIN, YOUNG-SOO KWON e CHUNGKYUN KIM. "ELECTRICAL AND OPTICAL PROPERTIES OF OLED USING NEW EMISSIVE MATERIAL Al2Nq4". International Journal of Nanoscience 05, n. 06 (dicembre 2006): 859–64. http://dx.doi.org/10.1142/s0219581x06005273.

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Since the first report of the light-emitting diodes based on Alq 3, many organic materials have been synthesized and extended efforts have been made to obtain high performance electroluminescent (EL) device. We synthesized new emissive material, 1, 4-dihydoxy-5, 8-naphtaquinone· Alq 3 complex( Al 2 Nq 4), and extended efforts have been made to obtain high-performance electroluminescent (EL) devices. Current–voltage (I–V) and luminance–voltage (L–V) characteristics were measured by Flat Panel Display Analysis System (Model 200-AT) at room temperature. The Al 2 Nq 4 shows green photoluminescence and electroluminescence spectra at about 510 nm, and ITO/Al 2 Nq 4/Cathode device shows typical rectifying characteristics.

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Sharypov, K. A., M. R. Ul'masculov, V. G. Shpak, S. A. Shunailov, M. I. Yalandin, G. A. Mesyats, V. V. Rostov e M. D. Kolomiets. "Current waveform reconstruction from an explosively emissive cathode at a subnanosecond voltage front". Review of Scientific Instruments 85, n. 12 (dicembre 2014): 125104. http://dx.doi.org/10.1063/1.4902853.

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Poulos, M. J. "Model for the operation of an emissive cathode in a large magnetized-plasma". Physics of Plasmas 26, n. 2 (febbraio 2019): 022104. http://dx.doi.org/10.1063/1.5063596.

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Oiler A. P., Liziakin G. D., Gavrikov A.V. e Smirnov V.P. "Velocity of plasma rotation in reflex discharge with themionic cathode". Technical Physics 92, n. 10 (2022): 1327. http://dx.doi.org/10.21883/tp.2022.10.54359.139-22.

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This work is devoted to determining the azimuthal ion rotation velocity in a reflex discharge with a thermionic cathode. For the experimental determination of the ion velocity, a Mach probe with directional particle collection was used. The Mach probe rotation velocity measurements are compared with the drift speed in crossed Ex B fields, where the radial electric field is measured with an emissive probe. The rotation of the plasma was found to be predominantly due to this drift, corrected for centrifugal effects. One of the important results of the work is the determination of the ion temperature. The obtained value Ti=0.12 eV, agrees with the ion temperature estimates in works with similar experimental conditions. A general parameter has been obtained that makes it possible to estimate the necessity to take into account centrifugal effects under given conditions. Keywords: plasma, thermionic cathode, reflex discharge, ion rotation, crossed fields.

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Liu, Wenxing, Rongzhen Cui, Xi Guan, Weidong Sun, Liang Zhou e Dashan Qin. "Investigating the exciton formation zone and its roles in phosphorescent organic light emitting diodes". Semiconductor Science and Technology 36, n. 12 (9 novembre 2021): 125014. http://dx.doi.org/10.1088/1361-6641/ac2fb5.

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Abstract The exciton formation zone has been studied in phosphorescent organic light emitting diodes (OLEDs). It is found that the width (W) of the exciton formation zone can be increased by reducing the transit time for holes (electrons) from the anode (cathode) into the emissive layer (EML) by decreasing the thickness of the hole (electron) transport layer. The increase in the thickness of the EML enables the exciton formation zone to be widened. The efficiency roll-off of the device is relieved when W increases. The device stability is found to be directly proportional to the product of W and the thickness of the electron transport layer. A thicker electron transport layer better suppresses diffusion of the metal cathode into the EML, increasing device stability but simultaneously decreasing the transit time for electrons from the cathode into the EML, and thereby W, so decreasing device stability. We also investigated the effect of charge carrier mobilities in the EML, modified by dye concentration, on W. The current research provides novel insights into guiding the delicate designs of OLEDs, hopefully pushing OLED technology towards high-luminance applications.

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Lv, Wenmei, Lian Wang, Yiwei Lu, Dong Wang, Hui Wang, Yuxin Hao, Yuanpeng Zhang, Zeqi Sun e Yongliang Tang. "A Study on the Field Emission Characteristics of High-Quality Wrinkled Multilayer Graphene Cathodes". Nanomaterials 14, n. 7 (30 marzo 2024): 613. http://dx.doi.org/10.3390/nano14070613.

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Field emission (FE) necessitates cathode materials with low work function and high thermal and electrical conductivity and stability. To meet these requirements, we developed FE cathodes based on high-quality wrinkled multilayer graphene (MLG) prepared using the bubble-assisted chemical vapor deposition (B-CVD) method and investigated their emission characteristics. The result showed that MLG cathodes prepared using the spin-coating method exhibited a high field emission current density (~7.9 mA/cm2), indicating the excellent intrinsic emission performance of the MLG. However, the weak adhesion between the MLG and the substrate led to the poor stability of the cathode. Screen printing was employed to prepare the cathode to improve stability, and the influence of a silver buffer layer was explored on the cathode’s performance. The results demonstrated that these cathodes exhibited better emission stability, and the silver buffer layer further enhanced the comprehensive field emission performance. The optimized cathode possesses low turn-on field strength (~1.5 V/μm), low threshold field strength (~2.65 V/μm), high current density (~10.5 mA/cm2), and good emission uniformity. Moreover, the cathode also exhibits excellent emission stability, with a current fluctuation of only 6.28% during a 4-h test at 1530 V.

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Georgiopoulou, Zoi, Apostolis Verykios, Kalliopi Ladomenou, Katerina Maskanaki, Georgios Chatzigiannakis, Konstantina-Kalliopi Armadorou, Leonidas C. Palilis et al. "Carbon Nanodots as Electron Transport Materials in Organic Light Emitting Diodes and Solar Cells". Nanomaterials 13, n. 1 (30 dicembre 2022): 169. http://dx.doi.org/10.3390/nano13010169.

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Charge injection and transport interlayers play a crucial role in many classes of optoelectronics, including organic and perovskite ones. Here, we demonstrate the beneficial role of carbon nanodots, both pristine and nitrogen-functionalized, as electron transport materials in organic light emitting diodes (OLEDs) and organic solar cells (OSCs). Pristine (referred to as C-dots) and nitrogen-functionalized (referred to as NC-dots) carbon dots are systematically studied regarding their properties by using cyclic voltammetry, Fourier-transform infrared (FTIR) and UV–Vis absorption spectroscopy in order to reveal their energetic alignment and possible interaction with the organic semiconductor’s emissive layer. Atomic force microscopy unravels the ultra-thin nature of the interlayers. They are next applied as interlayers between an Al metal cathode and a conventional green-yellow copolymer—in particular, (poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1′,3}-thiadiazole)], F8BT)—used as an emissive layer in fluorescent OLEDs. Electrical measurements indicate that both the C-dot- and NC-dot-based OLED devices present significant improvements in their current and luminescent characteristics, mainly due to a decrease in electron injection barrier. Both C-dots and NC-dots are also used as cathode interfacial layers in OSCs with an inverted architecture. An increase of nearly 10% in power conversion efficiency (PCE) for the devices using the C-dots and NC-dots compared to the reference one is achieved. The application of low-cost solution-processed materials in OLEDs and OSCs may contribute to their wide implementation in large-area applications.

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Labrunie, G., e R. Meyer. "Novel type of emissive flat panel display: the matrixed cold-cathode microtip fluorescent display". Displays 8, n. 1 (gennaio 1987): 37–40. http://dx.doi.org/10.1016/0141-9382(87)90007-2.

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Shin, Eun Chul, Hui Chul Ahn, Wone Keun Han, Tae Wan Kim, Won Jae Lee, Jin Woong Hong, Dong Hoe Chung e Min Jong Song. "Effect of Li2O/Al Cathode in Alq3 Based Organic Light-Emitting Diodes". Journal of Nanoscience and Nanotechnology 8, n. 9 (1 settembre 2008): 4684–87. http://dx.doi.org/10.1166/jnn.2008.ic33.

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An effect of bilayer cathode Li2O/Al was studied in Alq3 based organic light-emitting diodes with a variation of Li2O layer thickness. The current-luminance-voltage characteristics of ITO/TPD/Alq3/Li2O/Al device were measured at ambient condition to investigate the effect of Li2O/Al. It was found that when the thickness of Li2O layer is in the range of 0.5∼1 nm, there are improvements in luminance, efficiency, and turn-on voltage of the device. A current density and a luminance are increased by about 100 times, a turn-on voltage is lowered from 6 V to 3 V, a maximum current efficiency is improved by a factor of 2.3, and a maximum power efficiency is improved by a factor of 3.2 for a device with a use of thin Li2O layer compared to those of the one without the Li2O layer. These improvements are thought to be due to a lowering of electron-barrier height for electron injection from the cathode to the emissive layer.

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Guo, Tzung-Fang, Fuh-Shun Yang, Zen-Jay Tsai, Guan-Weng Feng, Ten-Chin Wen, Sung-Nien Hsieh, Chia-Tin Chung e Ching-In Wu. "High-brightness top-emissive polymer light-emitting diodes utilizing organic oxide/Al∕Ag composite cathode". Applied Physics Letters 89, n. 5 (31 luglio 2006): 051103. http://dx.doi.org/10.1063/1.2234317.

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Burgoa, José M., Cecilia González-Medina, Ramón Gómez-Aguilar e Jaime Ortiz-López. "Electrical Behavior I-V Theoretical-Experimental OLEDS". MRS Proceedings 1613 (2014): 121–26. http://dx.doi.org/10.1557/opl.2014.168.

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ABSTRACTWe develop a program (within MATLAB software environment) to numerically simulate current-voltage characteristics of a bilayer organic light-emitting diode (OLED). The program is based on the Poole-Frenkel and Schottky continuous quantum models which take into account the geometry of thin films and their emission parameters in the calculation of charge carrier and current density in organic materials. Simulations are performed for OLEDs with A/EML/C and A/HIL/EML/C architectures where A=anode, HIL=hole injection layer, EML=emissive layer and C=cathode. For EML we assume MEH-PPV and MDMO-PPV derivatives of poly-para-phenylene-vinylene (PPV) polymer semiconductor, and for HIL we use PEDOT:PSS. The results of simulation are compared with experimental results obtained from actual OLED devices constructed in our laboratory. For comparison we also use the commercial software SimOLED to simulate the devices under similar architectures. We find in general a fair agreement between the simulated and measured behavior except for a few orders of magnitude difference in the current.

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Tierno, S. P., J. M. Donoso, J. L. Domenech-Garret e L. Conde. "Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas". Physics of Plasmas 23, n. 1 (gennaio 2016): 013503. http://dx.doi.org/10.1063/1.4939042.

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Seif, Mujan N., T. John Balk e Matthew J. Beck. "Desorption from Hot Scandate Cathodes: Effects on Vacuum Device Interior Surfaces after Long-Term Operation". Materials 13, n. 22 (16 novembre 2020): 5149. http://dx.doi.org/10.3390/ma13225149.

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Scandate cathodes have exhibited superior emission properties compared to current state-of-the-art “M-type” thermionic cathodes. However, their integration into vacuum devices is limited in part by a lack of knowledge regarding their functional lifespan and behavior during operation. Here, we consider thermal desorption from scandate cathodes by examining the distribution of material deposited on interior surfaces of a sealed vacuum device after ~26,000 h of cathode operation. XPS, EDS, and TEM analyses indicate that on the order of 1 wt.% of the initial impregnate is desorbed during a cathode’s lifetime, Ca does not desorb uniformly with time, and little to no Sc desorbs from the cathode surfaces (or does so at an undetectable rate). Findings from this first-ever study of a scandate cathode after extremely long-time operation yield insight into the utility of scandate cathodes as components in vacuum devices and suggest possible effects on device performance due to deposition of desorption products on interior device surfaces.

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Vasan, R., H. Salman e M. O. Manasreh. "All inorganic quantum dot light emitting devices with solution processed metal oxide transport layers". MRS Advances 1, n. 4 (2016): 305–10. http://dx.doi.org/10.1557/adv.2016.129.

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ABSTRACTAll inorganic quantum dot light emitting devices with solution processed transport layers are investigated. The device consists of an anode, a hole transport layer, a quantum dot emissive layer, an electron transport layer and a cathode. Indium tin oxide coated glass slides are used as substrates with the indium tin oxide acting as the transparent anode electrode. The transport layers are both inorganic, which are relatively insensitive to moisture and other environmental factors as compared to their organic counterparts. Nickel oxide acts as the hole transport layer, while zinc oxide nanocrystals act as the electron transport layer. The nickel oxide hole transport layer is formed by annealing a spin coated layer of nickel hydroxide sol-gel. On top of the hole transport layer, CdSe/ZnS quantum dots synthesized by hot injection method is spin coated. Finally, zinc oxide nanocrystals, dispersed in methanol, are spin coated over the quantum dot emissive layer as the electron transport layer. The material characterization of different layers is performed by using absorbance, Raman scattering, XRD, and photoluminescence measurements. The completed device performance is evaluated by measuring the IV characteristics, electroluminescence and quantum efficiency measurements. The device turn on is around 4V with a maximum current density of ∼200 mA/cm2 at 9 V.

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Grigoriev, Sergei. "Milling of Dielectric Ceramics by Fast Argon Atoms". Key Engineering Materials 723 (dicembre 2016): 329–34. http://dx.doi.org/10.4028/www.scientific.net/kem.723.329.

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A new method for dielectric materials milling has been developed. Instead of well-known ion milling used for metals the dielectrics were processed by broad beams of fast argon atoms. The fast atoms were produced due to charge exchange collisions of accelerated ions. Plasma emitter of the ions was generated in hollow cathode glow discharge. Emissive grid of a circular cross-section beam source consisted of six segments. Energy of the fast atoms ranged from 1 to 3 keV. The beam source was used for production of contoured grooves on flat surfaces of hard ceramic materials. On the surface of movable seal ring made of α-corundum were produced grooves with depth of 20±0.5 μm and roughness of Ra ≈ 0.4 µm. The rate of α-corundum etching amounted to 3 μm/h.

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31

Arnas Capeau, C., G. Prasad, G. Bachet e F. Doveil. "Analysis of the self‐oscillations instability due to the plasma coupling with an emissive hot cathode sheath". Physics of Plasmas 3, n. 9 (settembre 1996): 3331–36. http://dx.doi.org/10.1063/1.871602.

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32

Lin, Ming-Wei, Ruei-Tang Chen, Chia-Hsin Yeh, Ten-Chin Wen e Tzung-Fang Guo. "Bright, efficient, deep blue-emissive polymer light-emitting diodes of suitable hole-transport layer and cathode design". Organic Electronics 13, n. 12 (dicembre 2012): 3067–73. http://dx.doi.org/10.1016/j.orgel.2012.09.009.

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33

Vincent, Benjamin, Sedina Tsikata, George-Cristian Potrivitu, Laurent Garrigues, Gaétan Sary e Stéphane Mazouffre. "Electron properties of an emissive cathode: analysis with incoherent thomson scattering, fluid simulations and Langmuir probe measurements". Journal of Physics D: Applied Physics 53, n. 41 (23 luglio 2020): 415202. http://dx.doi.org/10.1088/1361-6463/ab9974.

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34

Hao, Shi Ming, Hui Fang Wang e Dong Hui Zhao. "The Preparation and Properties Research on Lanthanum-Rich Film Cathode". Advanced Materials Research 228-229 (aprile 2011): 755–58. http://dx.doi.org/10.4028/www.scientific.net/amr.228-229.755.

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The surface lanthanum element plays a key role in emission mechanism of Lanthanum-contained cathodes. In order to gain insight into the relation between cathode emission properties and the cathode surface La/O ratio, lanthanum-rich film cathodes were prepared in situ by using a set of equipment, specially designed to cathode research, which connected with an Auger electron spectrometer (AES) and pulse laser deposition system. Electron emission properties and surface compositions (lanthanum and oxygen) of the cathodes are investigated experimentally. Experiment results indicate that film cathodes are lanthanum-rich film cathode, there has remained unchanged on film composition in different depth; the cathode emission properties are determined intensively by the surface atomic La/O ratios, the higher the La/O ratio gets, the better the emission property reaches. The excess active Lanthanum is crucial element to the improvement of emission properties.

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35

Ойлер, А. П., Г. Д. Лизякин, А. В. Гавриков e В. П. Смирнов. "Скорость вращения плазмы в отражательном разряде с термокатодом". Журнал технической физики 92, n. 10 (2022): 1529. http://dx.doi.org/10.21883/jtf.2022.10.53245.139-22.

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This work is devoted to determining the azimuthal ion rotation velocity in a reflex discharge with a thermionic cathode. For the experimental determination of the ion velocity, a Mach probe with directional particle collection was used. The Mach probe rotation velocity measurements are compared with the drift speed in crossed ExB fields, where the radial electric field is measured with an emissive probe. The rotation of the plasma was found to be predominantly due to this drift, corrected for centrifugal effects. One of the important results of the work is the determination of the ion temperature. The obtained value Ti=0.12 eV, agrees with the ion temperature estimates in works with similar experimental conditions. A general parameter has been obtained that makes it possible to estimate the necessity to take into account centrifugal effects under given conditions.

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36

Gioti, Maria. "Spectroscopic Ellipsometry Studies on Solution-Processed OLED Devices: Optical Properties and Interfacial Layers". Materials 15, n. 24 (19 dicembre 2022): 9077. http://dx.doi.org/10.3390/ma15249077.

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Τhe fabrication of organic light-emitting diodes (OLEDs) from solution involves the major problem of stack integrity, setting the determination of the composition and the characteristics of the resulting interfaces prerequisite for the optimization of the growth processes and the achievement of high devices’ performance. In this work, a poly(9,9-dioctylfluorene) (F8) and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) blend is used for the emissive layer (EML), poly-3,4-ethylene dioxythiophene; poly-styrene sulfonate (PEDOT:PSS) is used for a hole transport layer (HTL), and Poly(9,9-bis(3′-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluore-ne))dibromide (PFN-Br) for an electron transport layer (ETL) to produce the OLED device. All the layers are developed using the slot-die process, onto indium tin oxide (ITO)-coated polyethylene terephthalate (PET) flexible substrates, whereas Ag cathode was formed by ink-jet printing under ambient conditions. Spectroscopic ellipsometry measurements were performed upon completion of the successive films’ growth, in sequential steps, for the multilayer OLED development. Ellipsometry analysis using different models demonstrate the degree of intermixing within the layers and provide information about the interfaces. These interfacial properties are correlated with the emission characteristics as well as the final performance of the OLED devices.

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37

Hsieh, Sung-Nien, Ten-Chin Wen e Tzung-Fang Guo. "Improved Performance of Top-Emissive Polymer Light-Emitting Device with Semitransparent Ag Cathode with the Aid of Au Nanoparticles". Japanese Journal of Applied Physics 46, n. 3A (8 marzo 2007): 932–36. http://dx.doi.org/10.1143/jjap.46.932.

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38

Rathkey, Doug. "Evolution and Comparison of Electron Sources". Microscopy Today 1, n. 4 (giugno 1993): 16–17. http://dx.doi.org/10.1017/s1551929500067432.

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Over the years, we've seen major developments in electron source technologies in response to the demands for better performance. This article presents a brief overview of the cathode technologies in use today.Two types of electron sources are used in commercially available scanning electron microscopes (SEMs), transmission electron microscopes (TEMs), scanning Auger microprobes, and electron beam lithography systems: thermionic and field emission electron cathodes. Thermionic cathodes reiease electrons from the cathode material when they are heated while field emission cathodes rely on a high electric field to draw electrons from the cathode material.

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39

Swanson, L. W., e D. S. Rathkey. "A comparison of Schottky emission and cold field-emission cathodes". Proceedings, annual meeting, Electron Microscopy Society of America 47 (6 agosto 1989): 90–91. http://dx.doi.org/10.1017/s0424820100152422.

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We compare Schottky Emission (SE) and Cold Field Emission (CFE) cathodes with respect to emission characteristics and environmental factors. The CFE cathodes most commonly used are W<310> and a slightly oxidized W<100> used at room temperature. The SE cathode most commonly used is a ZrO coated W<100> emitter which has a localized work function of 2.8 ±0.2 eV on the <100> plane.In terms of emission mechanism, SE and CFE represent two extremes of a continuous change in surface electric field strength F and temperature T of a pointed cathode. The primary difference between a SE and CFE cathode is F, T, and energy distribution as shown in Fig. 1. TheSE cathode emission distribution contains mostly non-tunneling electrons terminated on the low energy side by the work function barrier. In contrast, the CFE emission distribution is defined by tunneling electrons terminated on the high energy side near the Fermi level of the metal.

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40

Taikin, Andrei Yu, Ilya A. Savichev, Maxim A. Popov, Evgeniy M. Anokhin, Viktor B. Kireev, Ilya N. Kosarev e Evgeniy P. Sheshin. "Comparison and analysis of field emission characteristics of carbon cathodes based on PAN fiber and CNT filaments". Image Journal of Advanced Materials and Technologies 7, n. 1 (2022): 046–57. http://dx.doi.org/10.17277/jamt.2022.01.pp.046-057.

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In this paper, we experimentally compare the field emission characteristics of two different cathodes based on polyacrylonitrile fibers (PAN fibers) and carbon nanotube fibers (CNT filaments). The main purpose of the study was to compare the field emission properties of materials for the cathode unit of a cathode luminescent lamp. The current-voltage, current and watt-watt characteristics of the fabricated cathodes were measured. A comparison of the current-voltage characteristics of cathodes made of the two studied materials shows that the minimum field for the occurrence of field emission current for a cathode made of a CNT filament (accelerating voltage in the diode version of measurements is about 625 V) is approximately 3 times lower than for a cathode made of PAN fibers (accelerating voltage is about 1850 V. Accordingly, the current value of about 100 μA for a cathode based on a CNT filament is achieved at an accelerating voltage of about 1300 V, and for a cathode based on PAN fibers, about 2630 V. Structural changes in cathodes were studied using scanning electron microscopy methods. Based on the totality of the results, it was concluded that it is preferable to use a CNT filament as a cathode material. The emission current of a cathode based on a CNT filament, when a constant high voltage is applied, demonstrates an increase during the transition period and reaches a stable value of more than 75 μA, apparently due to the activation of additional emission centers when a high accelerating voltage is applied. The paper also analyzes the factors that determine the efficiency of light sources created on the basis of the materials studied in the work.

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Li, Jian-quan, Xin-yao Xie, Shu-han Li e Qing-he Zhang. "Reliable potential and spatial size of virtual cathode obtained by an emissive probe with accurate filament temperature in a vacuum". Vacuum 200 (giugno 2022): 111013. http://dx.doi.org/10.1016/j.vacuum.2022.111013.

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42

Ng, Calvin Yi Bin, Keat Hoe Yeoh, Thomas J. Whitcher, Noor Azrina Talik, Kai Lin Woon, Thanit Saisopa, Hideki Nakajima, Ratchadaporn Supruangnet e Prayoon Songsiriritthigul. "High efficiency solution processed fluorescent yellow organic light-emitting diode through fluorinated alcohol treatment at the emissive layer/cathode interface". Journal of Physics D: Applied Physics 47, n. 1 (5 dicembre 2013): 015106. http://dx.doi.org/10.1088/0022-3727/47/1/015106.

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43

Predeep, P., T. A. Shahul Hameed, J. Aneesh e M. R. Baiju. "Organic Light Emitting Diodes: Effect of Annealing the Hole Injection Layer on the Electrical and Optical Properties". Solid State Phenomena 171 (maggio 2011): 39–50. http://dx.doi.org/10.4028/www.scientific.net/ssp.171.39.

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Organic Light Emitting Diodes (OLED) are receiving increased attention due to tremendous application potential these devices hold in the areas of large area displays and lighting applications. However, the problems of efficiency, stability and shelf life are major challenges for making OLEDs an attractive alternative. The simple device structure involving anode, emissive layer and cathode is no longer the norm. Recently, various buffer layers like Hole Injection Layer (HIL), Hole transport Layer (HTL), Electron Injection Layer (EIL), Electron Transport Layer (ETL) etc. are being widely used as integral parts of the OLED architecture to enhance the performance parameters. The nomenclature of these layers is often confusing and sometimes used by different authors to mean different layers and a common and universal nomenclature for layers is still wanting. Applying a buffer layer, often called as the hole injecting layer (HIL) between anode and emissive layer is a general technique for increasing the efficiency and stability of organic light emitting diodes. Poly- (3,4-ethyhylene dioxythiophene): poly- (styrenesulphonate) (PEDOT:PSS) is a very common and popular such HIL used in OLEDs. In this chapter, a basic structure of OLEDs has been discussed in perspective with this HIL material and the effect of annealing this PEDOT: PSS layer on the characteristics of the device at different temperatures ranging from 100°C to 300°C in vacuum. Devices fabricated in clean room conditions are characterized for their electrical and optical properties. Equivalent circuits of the devices are deduced using impedance spectroscopy and discussed. Surface morphology of the HIL layers using atomic force microscopy (AFM) provides reasons for the variation of the device properties with the annealing of HIL.

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Fairchild, Steven B., Chelsea E. Amanatides, Thiago A. de Assis, Paul T. Murray, Dmitri Tsentalovich, Jeffrey L. Ellis, Salvador Portillo et al. "Field emission cathodes made from knitted carbon nanotube fiber fabrics". Journal of Applied Physics 133, n. 9 (7 marzo 2023): 094302. http://dx.doi.org/10.1063/5.0123120.

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Field electron emission cathodes were constructed from knitted fabrics comprised entirely of carbon nanotube (CNT) fibers. The fabrics consisted of a top layer array of ∼2 mm high looped structures and a bottom layer that was 1 mm thick with a flat underlying surface. Field emission (FE) experiments were performed on 25.4 mm diameter CNT fabric cathodes in both direct current (DC) and pulsed voltage (PV) modes, and the results were compared to those obtained from a CNT film cathode. The DC measurements were performed at a maximum voltage of 1.5 kV. The CNT fabric cathode emitted 20 mA, which was an 8× increase over the emission current from the CNT film cathode. The DC results were analyzed using the corrected form of the Fowler–Nordheim FE theory initially developed by Murphy and Good, which allows for the determination of the formal emission area and effective gap-field enhancement factor. The PV experiments resulted in Ampere level emission currents from both CNT fabric and CNT film cathodes. For a 25 kV, 500 ns voltage pulse, the CNT fabric cathode emitted 4 A, which was 2× more current than the CNT film cathode. Scanning electron microscopy imaging after PV testing revealed that the fibers remained intact after >5000 pulses. These results indicate that knitted CNT fabrics offer a promising approach for developing large area, conformable, robust FE cathodes for vacuum electronic devices.

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45

Gorokh, G. G., I. A. Taratyn, A. N. Pligovka, A. A. Lazavenka e A. I. Zakhlebayeva. "AUTOELECTRONIC CATHODES BASED ON ARRAYS OF NIOBIUM-OXIDE COLUMNAR NANOSTRUCTURES FOR FIELD EMISSION DISPLAYS". Doklady BGUIR, n. 7 (125) (7 dicembre 2019): 51–58. http://dx.doi.org/10.35596/1729-7648-2019-125-7-51-58.

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The article discusses the prospects of creating controlled field-effect cathodes based on arrays of columnar oxide niobium nanostructures for field emission displays. Geometrical models of field-emission cathodes and vacuum elements have been developed and investigated. The distribution of the electric field in the vacuum device at various distances between the cathode and the anode, the applied voltages between them, the shape and microgeometry of the cathodes were obtained. The optimal geometric parameters of nanostructured autoelectronic cathodes and matrices of these were calculated based on the simulation. The technological route has been developed for the production of autoelectronic cathode matrices based on arrays of niobium-oxide columnar nanostructures formed by electrochemical anodization of Al/Nb thin-film system. The samples of controlled arrays of autoelectronic cathodes were fabricated and the current-voltage characteristics with interelectrode gap of 2, 5 and 10 μm in various electric modes with change in the electric field strength from 3 to 85 V/μm were studied. At 2 μm gap between the anode and cathode, the emission occurs at minimum threshold voltages, but it is characterized by limited current values. The increasing in the interelectrode gap allows rising the emission currents, however, the threshold voltages increase. In the pulsed mode, the large emission currents are achieved. The threshold voltage of autoelectronic cathode matrices with interelectrode gap of 5 μm was 9.16 V, the maximum currents reached 350 μA at voltage of 22.5 V. In the pulsed mode, the emission arose at 11.06 V, the maximum current reached 1500 μA at 40 V.

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46

Chepusov, A. S., A. A. Komarskiy e S. R. Korzhenevskiy. "Investigation of changes in field electron emission characteristics of industrial fine-grained graphite when operated in an argon atmosphere up to 10^–2 Pa". Journal of Physics: Conference Series 2064, n. 1 (1 novembre 2021): 012107. http://dx.doi.org/10.1088/1742-6596/2064/1/012107.

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Abstract Studying of field electron emission properties of carbon cathodes operating under technical vacuum conditions is a promising scientific field. Massive cathode made of commercial fine-grained graphite of MG (Russian abbreviation) grade is being investigated. Experiments on obtaining current-voltage characteristics and long-term testing are being carried out. The emitter made of fine-grained graphite demonstrates good emission properties under technical vacuum conditions. Carbon cathode is capable of operating at pressures up to 2×10–2 Pa. Increased pressure in the vacuum chamber leads to deterioration of cathode emission properties. Electric field enhancement factors were calculated for all stages of studies. Analysis of experimental data demonstrates decrease in enhancement factor due to ion bombardment of cathode surface during exploitation. This results in higher electric field for operation of investigated graphite cold cathodes.

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47

Roy, Amitava, R. Menon, Vishnu Sharma, Ankur Patel, Archana Sharma e D. P. Chakravarthy. "Features of 200 kV, 300 ns reflex triode vircator operation for different explosive emission cathodes". Laser and Particle Beams 31, n. 1 (27 novembre 2012): 45–54. http://dx.doi.org/10.1017/s026303461200095x.

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AbstractTo study the effect of explosive field emission cathodes on high power microwave generation, experiments were conducted on a reflex triode virtual cathode oscillator. Experimental results with cathodes made of graphite, stainless steel nails, and carbon fiber (needle type) are presented. The experiments have been performed at the 1 kJ Marx generator (200 kV, 300 ns, and 9 kA). The experimentally obtained electron beam diode perveance has been compared with the one-dimensional Child-Langmuir law. The cathode plasma expansion velocity has been calculated from the perveance data. It was found that the carbon fiber cathode has the lowest cathode plasma expansion velocity of 1.7 cm/μs. The radiated high power microwave has maximum field strength and pulse duration for the graphite cathode. It was found that the reflex triode virtual cathode oscillator radiates a single microwave frequency with the multiple needle cathodes for a shorter (<200 ns full width at half maximum) voltage pulse duration.

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48

Lobanov, Svyatoslav V., Ivan A. Fedorov e Evgeniy P. Sheshin. "DEVELOPING MANUFACTURING TECHNOLOGY OF COMPOSITE CATHODES WITH METHOD OF PRESSING PYROLYTIC GRAPHITE WITH TRIPLE CARBONATE". IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 59, n. 8 (17 luglio 2018): 81. http://dx.doi.org/10.6060/tcct.20165908.29y.

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In this work a manufacturing technology for a composite cathode is described. In this cathode draphite and emission-active substance forms intercalated chemical compound. These cathodes were studied in a mode of field thermo electrone emission at temperatures of 0-1100 ° C and anode voltages of 1 – 15 kV. The article contains results of determination of optimal pressing parameters, different methods of cathode surface processing and field emission current-voltage characteristics.

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Wu, Ping, Jiayao Liu, Ye Hua e Meng Zhu. "Quantitative evaluation of emission uniformity of the annular explosive emission cathode". Physics of Plasmas 29, n. 11 (novembre 2022): 113101. http://dx.doi.org/10.1063/5.0121618.

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Explosive emission cathodes (EECs) are widely used in the field requiring intense electron beams. The uniform emission of EECs is vital for applications. To effectively evaluate the emission uniformity of annular EECs, this paper proposes a quantitative evaluation model based on the analysis of cathode plasma images and constructs a parameter which is named as the non-uniformity value to describe the extent of emission uniformity. The experiment designed to investigate the cathode emission uniformity under different circumstances demonstrates that the model is valid. The experimental results give quantitative information of uniformity change in explosive emission and show that the non-uniformity values of graphite and aluminum cathodes can be significantly decreased by increasing the guiding magnetic field and the diode voltage.

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Lee, Ha Rim, Da Woon Kim, Alfi Rodiansyah, Boklae Cho, Joonwon Lim e Kyu Chang Park. "Investigation of the Effect of Structural Properties of a Vertically Standing CNT Cold Cathode on Electron Beam Brightness and Resolution of Secondary Electron Images". Nanomaterials 11, n. 8 (26 luglio 2021): 1918. http://dx.doi.org/10.3390/nano11081918.

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Carbon nanotube (CNT)-based cold cathodes are promising sources of field emission electrons for advanced electron devices, particularly for ultra-high-resolution imaging systems, due to their high brightness and low energy spread. While the electron field emission properties of single-tip CNT cathodes have been intensively studied in the last few decades, a systematic study of the influencing factors on the electron beam properties of CNT cold cathodes and the resolution of the secondary electron images has been overlooked in this field. Here, we have systematically investigated the effect of the structural properties of a CNT cold cathode on the electron beam properties and resolution of secondary electron microscope (SEM) images. The aspect ratio (geometric factor) and the diameter of the tip of a vertically standing CNT cold cathode significantly affect the electron beam properties, including the beam size and brightness, and consequently determine the resolution of the secondary electron images obtained by SEM systems equipped with a CNT cold cathode module. Theoretical simulation elucidated the dependence of the structural features of CNT cold cathodes and electron beam properties on the contribution of edge-emitted electrons to the total field emission current. Investigating the correlations between the structural properties of CNT cold cathodes, the properties of the emitted electron beams, and the resolution of the secondary electron images captured by SEM equipped with CNT cold cathode modules is highly important and informative as a basic model.

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