Trade-off in perpendicular electric field control using negatively biased emissive end-electrodes

The benefits of thermionic emission from negatively biased electrodes for perpendicular electric field control in a magnetized plasma are examined through its combined effects on the sheath and on the plasma potential variation along magnetic field lines. By increasing the radial current flowing through the plasma thermionic emission is confirmed to improve control over the plasma potential at the sheath edge compared to the case of a cold electrode. Conversely, thermionic emission is shown to be responsible for an increase of the plasma potential drop along magnetic field lines in the quasi-neutral plasma. These results suggest that there exists a trade-off between electric field longitudinal uniformity and amplitude when using negatively biased emissive electrodes to control the perpendicular electric field in a magnetized plasma.

Электронная структура вариантов составов скандатных и оксидно-никелевых катодов СВЧ приборов

By methods of electron spectroscopy for chemical analysis and spectroscopy of characteristic losses of electron energy, the electronic structure of barium oxide crystallites doped with other chemical elements, including scandium from scandium-containing phases, was investigated. The physical and physicochemical conditions are formulated, the fulfillment of which allows to form the electronic structure of the scandate cathode with a high level of thermionic emission: the achievement of the minimum ratio of the surface volume concentration of oxygen vacancies and the maximum distance between the top of the valence band and the Fermi level.

Thermionic electron emission in the 1D edge-to-edge limit

Thermionic emission is a tunneling phenomenon, which depicts that electrons on the surface of a conductor can be pulled out into the vacuum when they are subjected to high electrical tensions while being heated hot enough to overtake their work functions. This principle has led to the great success of the so-called vacuum tubes in the early 20th century. To date, major challenges still remain in the miniaturization of a vacuum channel transistor for on-chip integration in modern solid-state integrated circuits. Here, by introducing nano-sized vacuum gaps (~200 nm) in a van der Waals heterostructure, we successfully fabricated a one-dimensional (1D) edge-to-edge thermionic emission vacuum tube using graphene as the filament. With the increasing collector voltage, the emitted current exhibited a typical rectifying behavior, with the maximum emission current reaching 200 pA and an On-Off ratio of 103. Besides, it is found that the maximum emission current was proportional to the number of the layers of graphene. Our results expand the studies of the nano-sized vacuum tube to an unexplored physical limit of 1D edge-to-edge emission, and hold great promise for future nano-electronic systems based on it.

Comparison of the electrical and impedance properties of Au/(ZnOMn:PVP)/ n-Si (MPS) type Schottky-diodes (SDs) before and after gamma-irradiation

The effect of 60Co-irradiation) on the electrical parameters in the Au/(ZnOMn:PVP)/n-Si SDs has been investigated using the current-voltage (I-V) and capacitance/conductance-voltage (C/G-V) measurements. Firstly, the values of reverse-saturation-current (Io), ideality-factor (n), barrier-height (BH), shunt/series resistances (Rsh, Rs), and rectifying-rate (RR) were extracted from the I-V data before and after gamma-irradiation (5 and 60 kGy) using thermionic-emission (TE), Norde, and Cheung methods. The surface-states (Nss) versus energy (Ec-Ess) profile was extracted from I-V data considering voltage-dependent of n and BH using the Card-Rhoderick method. Secondly, the doping-donor atoms (Nd), Fermi-energy (EF), BH, maximum electric-field (Em), and depletion-layer width (Wd) were extracted from the linear-part of reverse-bias C-2-V plot for 100 kHz before and after irradiation. Finally, the voltage-dependent profiles of Rs and radiation-induced of Nss were extracted from the C/G-V plots by using Nicollian-Brews and the difference between C-V plots before and after irradiation, respectively. The peak behavior in the Nss-V plots and shifts in its position was attributed to special-distribution of Nss at (ZnOMn:PVP)/n-Si interface and restructure/reordering of them under radiation and electric field. Experimental results show that gamma-irradiation is more effective both on the I-V and C/G-V plots or electrical parameters, and hence the fabricated Au/(ZnOMn:PVP)/n-Si SDs can be used as a radiation-sensor.

Barrier properties and current conduction mechanism for metal contacts to lightly and highly doped p-type 4H-SiC

The barrier properties of Ti, Ni and Pt contact to lightly (9×1016 cm-3) and highly (9×1018 cm-3) doped p-type 4H-SiC were investigated. It is found that the barrier heights and ideality factors estimated from thermionic emission model for the lightly doped samples are non-ideal and abnormally temperature dependent. The anomalies have been successfully explained in terms of both pinch-off model and Gaussian distribution of inhomogeneous barrier heights. In addition, the evaluated homogeneous barrier heights are reasonably close to the average barrier heights from capacitance-voltage measurements. For the highly doped samples, thermionic field emission (TFE) is found to be the dominant carrier transport mechanism. The barrier heights estimated from TFE model are temperature independent. If the barrier inhomogeneities and tunneling effects are considered, the experimental results of the samples are in well agreement with the theoretical calculations.