Gate Control of Superconductivity in Mesoscopic All-Metallic Devices

The possibility to tune, through the application of a control gate voltage, the superconducting properties of mesoscopic devices based on Bardeen–Cooper–Schrieffer metals was recently demonstrated. Despite the extensive experimental evidence obtained on different materials and geometries, a description of the microscopic mechanism at the basis of such an unconventional effect has not been provided yet. This work discusses the technological potential of gate control of superconductivity in metallic superconductors and revises the experimental results, which provide information regarding a possible thermal origin of the effect: first, we review experiments performed on high-critical-temperature elemental superconductors (niobium and vanadium) and show how devices based on these materials can be exploited to realize basic electronic tools, such as a half-wave rectifier. Second, we discuss the origin of the gating effect by showing gate-driven suppression of the supercurrent in a suspended titanium wire and by providing a comparison between thermal and electric switching current probability distributions. Furthermore, we discuss the cold field-emission of electrons from the gate employing finite element simulations and compare the results with experimental data. In our view, the presented data provide a strong indication regarding the unlikelihood of the thermal origin of the gating effect.

Термоавтоэлектронная эмиссия из квантовых точек антимонида индия

The paper identifies and analyzes the features of the mechanism of field emission in the tunneling microscope probe – indium antimonide quantum dot system in the temperature range of 23—150 °C. The analysis of the tunneling CVCs made it possible to conclude that there are different mechanisms of electron transfer from the metal probe of the tunneling microscope and the field emission of electrons through discrete energy levels of the indium antimonide quantum dot at different temperatures.

The temperature dependence of the work function of oxide electrodes in fluorescent lamps

In the present work the temperature dependence of the work function of oxide cathodes in operating fluorescent lamps was investigated experimentally. A detailed review on the theory is presented, including a thermodynamic and a quantum mechanical view on the problem. Aspects such as the role of the electrochemical potential, external and internal potentials, the constituents of the electron affinity, the patch effect and surface states are discussed. For solids in contact the Volta and Galvani potentials are related to their work functions. The importance of colour centres in oxide electrodes on the temperature dependence of the work function and the impact of ultraviolet radiation is emphasized. The measurements have been carried out under zero field emission of electrons from the electrode, using the Waymouth (rf) and Eisenmann (visual) methods as indicators. By inserting an empirical ansatz into the Richardson equation, it was possible to determine the temperature dependence of the work function from the experiments.

Effect of heating and resistance on emission properties of carbon nanotubes

We have studied the effect of the series resistance on the heating of the cathode, which is based on carbon nanotubes and serves to realize the field emission of electrons into the vacuum. The experiment was performed with the single multi-walled carbon nanotube (MCNT) that was separated from the array grown by CVD method with thin-film Ni-Ti catalyst (nickel 4 nm / Ti 10 nm). The heating of the cathode leads to the appearance of a current of the thermionic emission. The experimental voltage current characteristic exhibited the negative resistance region caused by thermal field emission. This current increases strongly with increasing voltage and contributes to the degradation of the cold emitter. The calculation of the temperature of the end of the cathode is made taking into account the effect of the phenomenon that warms up and cools the cathode. We have developed a method for processing of the emission volt-ampere characteristics of a cathode, which relies on a numerical calculation of the field emission current and the comparison of these calculations with experiments. The model of the volt-ampere characteristic takes into account the CNT’s geometry, properties, its contact with the catalyst; heating and simultaneous implementation of the thermionic and field emission. The calculation made it possible to determine a number of important parameters, among which the voltage and current of the beginning of thermionic emission, the temperature distribution along the cathode, the resistance of the nanotube. The phenomenon of thermionic emission from CNT’s was investigated experimentally and theoretically. The conditions of this type emission occurrence were defined. The results of the study could form the basis of theory of CNT emitter’s degradation.