A Comparative Study On Electronic Transport Behavior Of Silicene And B40-Nano Onions

Density Functional Theory is utilized to scrutinize the electronic state of silicene and boron nano-onion which is a round compact mass formed by placing an N20, C20, and B20 fullerene within its parent atom fullerene B40. NEGF was used to investigate the quantum transport at both equilibrium and non-equilibrium. Firstly, the I-V curve for both silicene and boron-based devices was studied and compared. From the results, it is concluded that boron-based devices are better than silicene. To get deeper insights into why boron-based devices are better than silicene, transport properties of boron-based devices were determined. Later on, the transport mechanism is analyzed by computing the DOS, transmission and molecular spectra, HLG, electron densities, and differential conductance when the boron nano-onion is placed between the pair of Au electrodes. The calculated results are evaluated and a comparative study is done. From the results, it is deduced that the N20 variant nano-onion has lesser HOMO-LUMO gap (HLG) and highest value of current in comparison to other devices. Thus, by infusing a smaller fullerene of N20 inside the hollow cage of B40 fullerene the amplification of current and conductance can be observed in Boron-nano-onion in comparison to other devices.

What Happens When the Electron Beam Hits the Specimen

When an electron passes through matter, the energy of the electron is transferred to the material in the form of ionizations and excitations. Almost all of this transfer is the result of the Coulomb interaction of the beam electrons with the electrons in the specimen; that is, scattering of beam electrons by nuclei is not an important energy-transfer process.On average, about 30 eV is transferred for each ion pair (the electron and the parent atom) produced, and most of the energy transferred goes into primary or secondary ionizations. In a typical energy-loss process, an electron can be removed from an inner shell (it can leave the atom with a velocity comparable to that of the incident electron).

The nuclear β-rays of radium D

The radium D. E. disintegration is of special interest because of the very low energy of the disintegration electrons. It appears probable that more than half of these are emitted with less than 4 kV energy so that the energy change is less than in any other known nuclear disintegration. While there has been much uncertainty about the energies of the nuclear electrons, certain other facts about the transformation appear to be well established. In nearly every disintegration the product nucleus of radium E is left excited 47 kV above the ground-level. The resulting γ-ray is very strongly internally converted in the L and outer atomic levels so that only about 3-5 γ-quanta escape from the parent atom in 100 disintegrations. These results have been established by expansion chamber observations of the β-rays and by observations of the effects produced by the unconverted 47 kV γ-quanta (Bramson 1930; Stahel and Sizoo 1930) and the L charac­teristic X -radiation which is emitted as a consequence of the ejection of a secondary β-ray from the L level by the internal conversion (von Droste 1933; Stahel 1935).

The absolute intensities and internal conversion coefficients of the y-rays of radium B and radium C

It is well known that with many radioactive bodies the departure of the disintegration particle is followed by the emission of γ-rays. In addition to γ-rays of frequencies v 1 , v 2 , ..., it is observed that there is an electronic emission consisting of several homogeneous groups whose energies can be written The energies of these groups are identical with those that would be produced by photoelectric absorption in the parent atom of the γ-rays emitted from the nucleus, and this phenomenon is frequently described as the internal conversion of γ-rays. By this is meant that in every case when the nucleus emits energy E this occurs in the form of radiation of frequency E/ h , but that this does not always escape as such from the atom. In a fraction a of the cases the radiation is absorbed in the electronic structure and gives rise to a photoelectron, in the remaining fraction (1 — α) the γ-ray is emitted clear of the atom. The quantity a is termed the coefficient of internal conversion. Smekal* and others have pointed out that there is no need and even no justification to consider the γ-ray ever to be emitted in the case of those atoms which give photoelectrons. All that can be truly inferred from the experimental facts is that the atom as a whole is capable of emitting energy E, and this it may do either in the form of a quantum of radiation hv = E, or in the form of an electron of energy E — K, or E — L, etc., followed by the appropriate excited K-, L-, X-radiations. The greater portion of this energy E is certainly resident in the nucleus, so that this second standpoint implies some type of what may be termed collision interaction between the nucleus and the electronic structure of the atom.

Speculations concerning the α-, β- and γ-Rays of Ra B, C, C.- Part I. A revised theory of the interval absorption coefficient

1. Introduction .- It is well known that the γ-ray emitted by radioactive nuclei are often very strongly absorbed in a species of photoelectric effect by the planetary electrons of the parent atom, thus giving rise to the sharp lines of the β-ray spectrum. The recent work of Ellis and Aston provides numerical values of this “internal conversion coefficient” of the γ-rays from Ra BC and Ra CCD-data which bring out more clearly than hitherto the curiosities of this coefficient (see Table I below). The present paper is the outcome of repeated discussions between Dr. Ellis and the author about possible explanations of the data. All the preliminary work was carried out in collaboration, and it was our original intention to publish our results jointly. This has proved impossible, so that the responsibility for the corrections of the calculations of this paper rests entirely on me. But the work could not have been attempted without Dr. Ellis’s help. Ellis and Aston find that this coefficient behaves so differently for different classes of β-ray line that one is even sometimes tempted to suspect a different mechanism of emission. The rather soft γ-rays of Ra BC are converted by the K-level electrons in fractions of the surprising size of 10 percent. To 25 percent., varying in a normal manner with the frequency. The harder γ-rays of Ra CC’D fall, however, into three groups. The main γ-rays of energy from 6·12 X 10 5 to 12·48 X 10 5 volts have a practically constant conversion fraction of about 0·006; those from 13·90 X 105 to 22·19 X 10 5 volts a similar constant fraction now about 0·006; those from 13.90 X 10 5 to 22·19 X 10 5 volts a similar constant fraction now about 0·0015. All these γ-rays, though most easily studied via their derived natural β-ray lines undoubtedly can be studied as γ-rays outside their parent atom. But there is a third group containing one outstanding γ-ray of 14·26 X 10 5 volts energy whose existence has been inferred only from certain associated β-ray lines, among the strongest in the spectrum. (if is it a γ-ray) is so strongly converted in the parent atom that it is doubtful if it has ever been observed as a γ-ray at all. It would be consistent with (though not necessitated by) the evidence, to assert that it is a γ-ray with an internal conversion factor unity.

Particles of long range emitted by the active deposits of radium, thorium and actinium

For a considerable time after the discovery of radio-activity, it was thought that all the α-rays emitted by a given substance possessed a definite velocity and hence a definite range. It was shown, however, by Hahn, in 1906, that the active deposit of thorium emitted two distinct sets of α-rays with ranges 4·8 and 8·6 cm. respectively. Although these were at first thought to arise from successive products, it was subsequently established that they were the result of two different methods of the disintegration of the parent atom, thorium C. Marsden and Barratt were able to show that when thorium C breaks up, 65 per cent. of the atoms contribute α-rays of the longer range and 35 per cent. of the shorter. In 1911, Fajans, in investigating the recoil atoms from radium active deposit, discovered a new product radium C'' which had a half-value period of 1.38 minutes. The fraction of the radium C atoms, which disintegrated with the formation of this product, was found to be only 3 in 10,000. In 1914, Marsden and Perkins discovered that actinium C emitted a small number of particles whose range was 6·4 cm. This was followed in 1916 by Rutherford and Wood's discovery of a few particles of range 11·3 cm. from thorium active deposit, and finally in 1919 Rutherford established the presence of particles or range 9·0 cm. from radium active deposit. It will be noticed that, in all these cases except the first cited, the large majority of the atoms break up in what might be termed the "normal" manner, while comparatively few produce α-rays of range different from the normal range. The above results suggested that perhaps the various active deposits emitted, in even smaller numbers, other particles of definite ranges, and a thorough search was undertaken by means of the scintillation method for particles of long range, advantage being taken of the great improvements which have recently been achieved in the methods of counting α-particles. These methods involve the use of microscopes specially designed to increase the brightness of the scintillations observed and in particular to increase the area of the zine sulphide screen, and consequently the number of scintillations, under observation. The microscope used in the present research was of the type described by Rutherford and Chadwick, with a holoscopic objective of numerical aperture 04∙5 and 16 mm. focal length, together with a specially constructed eye-piece consisting of two large plano-convex lenses and a smaller double convex eye-lens. The field of view was about 20 Sq. mm. in area, whilst the fields formerly employed rarely exceeded 3 sq. mm. We have thus been able without greatly increasing the intensity of the radioactive sources to detect the presence of several groups of particles from the active deposits of radium and thorium which had previously not been observed.