Thermionic emission

About: Thermionic emission is a research topic. Over the lifetime, 6099 publications have been published within this topic receiving 97892 citations. The topic is also known as: Edison effect.

W-TiN-SiC Materials for High Temperature Application

Abstract: A composite W-TiN-SiC material, as well as the technology for the manufacture of this material, are being developed at the Centre for Technical Ceramics in co-operation with partners in Italy and the Netherlands. The trilayer material will serve as a multifunctional “hot shell” in a combustion heated Thermionic Energy Converter. This device will operate at 1400°C. The composite material simultaneously serves as a protective confinement of the converter, as an emitter electrode and as an electrical lead. The multitude of requirements induced by these three functions of the hot shell are discussed. A brief outline of the design of the thermionic energy converter is given. The way in which the W-TiN-SiC material is being produced as well as some preliminary results on the evaluation of this material are presented. The properties determined include thermal fatigue and thermoshock resistance, Young’s modulus and thermal conductivity. Although the evaluation is still in progress, the results are promising.

Theory of the retarding potential method of cathode temperature measurement

Abstract: Retarding potential measurements can be used to determine the temperature of the cathode in a traveling wave tube. General expressions are derived for the current in a thermionic diode as a function of cathode temperature and applied voltage. An enumeration is made of the conditions under which such expressions can be reduced to a form that enables application of the retarding potential method of temperature measurement. An integral form is given for the factor needed to generalize the Richardson equation to more general geometry, and it is evaluated for a special case. Finally, there is a discussion of the case when, because of surface or other effects, the distribution function of emitted electrons is not given by the Fermi–Dirac distribution.

Field and Thermal Emission Limited Charge Injection in Au–C60–Graphene van der Waals Vertical Heterostructures for Organic Electronics

Abstract: Among the family of 2D materials, graphene is the ideal candidate as top or interlayer electrode for hybrid van der Waals heterostructures made of organic thin films and 2D materials due to its high conductivity and mobility and its inherent ability of forming neat interfaces without diffusing in the adjacent organic layer. Understanding the charge injection mechanism at graphene/organic semiconductor interfaces is therefore crucial to develop organic electronic devices. In particular, Gr/C60 interfaces are promising building blocks for future n-type vertical organic transistors exploiting graphene as tunneling base electrode in a two back-to-back Gr/C60 Schottky diode configuration. This work delves into the charge transport mechanism across Au/C60/Gr vertical heterostructures fabricated on Si/SiO2 using a combination of techniques commonly used in the semiconductor industry, where a resist-free CVD graphene layer functions as a top electrode. Temperature-dependent electrical measurements show that the transport mechanism is injection limited and occurs via Fowler–Nordheim tunneling at low temperature, while it is dominated by a nonideal thermionic emission at room and high temperatures, with energy barriers at room temperature of ca. 0.58 and 0.65 eV at the Gr/C60 and Au/C60 interfaces, respectively. Impedance spectroscopy confirms that the organic semiconductor is depleted, and the energy band diagram results in two electron blocking interfaces. The resulting rectifying nature of the Gr/C60 interface could be exploited in organic hot electron transistors and vertical organic permeable-base transistors.

Deep levels and conduction processes in nitrogen-implanted Ga2O3 Schottky barrier diodes

Abstract: In this paper, we analyze the electrical behavior and the deep levels present in nitrogen-implanted gallium oxide Schottky barrier diodes annealed at increasing temperature from 800 °C to 1200 °C. In gallium oxide, nitrogen implantation is used in order to achieve controlled isolation of parts of the final device, and its stability and performance is therefore of high importance. The high temperature annealing carried out after implantation causes a reduction in the leakage current flowing in the structure, confirming the feasibility of nitrogen implantation as isolation procedure and the annealing of the defects caused by the implantation process. Repeated current-voltage measurements show the presence of an electron trapping process in the structure. The involved deep levels were investigated by means of isothermal transient spectroscopy tests, and both current and capacitance were used to monitor the trapping level in the devices. A model was developed to explain the full set of collected data on all the annealing temperatures, based on thermionic injection of electrons into an intermediate deep level and on charge injection into the space charge region. By means of deep level transient spectroscopy experiments we analyzed the various defects present in the samples. Their concentration correlates with the annealing, decreasing at high temperature. All the detected deep levels are consistent with previous reports in the literature, and are attributed to gallium vacancies, native point defects and extrinsic defects.

Investigation of photon-induced effects on some diode parameters and negative capacitance of the Schottky structure with Zn-doped organic polymer (PVA) interface

Abstract: Variation in the electrical parameters depending on illumination and the formation of negative capacitance (NC), and inductive behavior (IB) of Schottky structures interlaid with Zn:PVA, were executed by current/impedance-voltage (I/Z-V) measurements in the dark and under 200 mW cm−2 illuminance. To designate the voltage or calculation method effects on the ideality factor (n), barrier height (BH-Φ B ), and series resistance (R s ), these parameters were extracted from different methods. These parameters extracted through the Thermionic-emission (TE) theory, Ohm’s law, Norde and Cheung functions were compared with each other. The reverse bias ln(I R )−V R 0.5 plots were also drawn to designate the validity of Poole-Frenkel and Schottky emissions. In Z-V measurements, NC and related IB phenomena were observed at 500 kHz-fixed frequency in the dark and under illuminance. The interface states (D it ) variation depending on energy and voltage was obtained using I-V and C/G-V measurements and related equations. The calculations of the diffusion-potential (V D ), acceptor-atoms (N A ), Fermi-energy (E F ), and Φ B (C-V) values were performed by fitting the observed linear in the reverse bias C −2 -V plot. A detailed analysis of NC was performed via the drawn C/(G/ω)-I plots for positive voltages. All experimental results show that the used calculation method, illumination, and voltage are highly effective on the electrical parameters.