scholarly journals Total secondary electron emission from polycrystalline Nickel

1930 ◽  
Vol 128 (807) ◽  
pp. 41-56 ◽  
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Considerable Proportion ◽  
Secondary Beam ◽  
X Rays ◽  
Applied Potential ◽  
Polycrystalline Nickel ◽  
Low Velocity ◽  
Secondary Electrons

The importance of secondary electron emission in its relation to the excitation of soft X-rays has been pointed out in a recent paper by Prof. O. W. Richardson. He has shown that at every potential where there is an increased excitation of soft X-rays, there is correspondingly an increase in the emission of secondary electrons, and has discussed at some length the mechanism of the generation of secondary electrons. It was therefore felt that a much clearer idea of the phenomenon of soft X-ray excitation from metallic surfaces could be had by studying the secondary electron emission from polycrystalline and single crystal faces. As early as in 1908 Richardson showed that slowly moving electrons are reflected in considerable proportion from metallic plates. Davisson and Kunsman, in a series of papers commencing from 1921, showed that at low voltages up to about 9 volts most of the secondary electrons were purely reflected electrons with velocities the same as the incident electrons. The percentage of the reflected electrons fell rapidly as the applied potential was increased above 9 volts, while that of low velocity electrons increased steadily. Farnsworth, with improved apparatus, added much valuable information regarding the generation of secondary electrons and the conditions operating in such cases. These observers showed that the total emission of secondary electrons from a metal surface depended on the applied potential, the nature of the surface and the previous heat treatment of the metal. They also found that the ratio of the secondary beam to the primary increases with applied potential and becomes greater than 1 after a certain potential, depending on the nature of the bombarded metal, is reached.

scholarly journals The efficiency of secondary electron emission

1933 ◽  
Vol 139 (838) ◽  
pp. 436-447 ◽  
Keyword(s):  
Velocity Distribution ◽  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Inelastic Collisions ◽  
Secondary Beam ◽  
X Rays ◽  
Secondary Electrons ◽  
The Third ◽  
Primary Electrons

The velocity distribution of the secondary electrons produced by bombarding a metallic face with a stream of primary electrons has been a matter of interest ever since the beginning of the study of secondary electron emission. As early as in 1908, Richardson and von Baeyer independently showed that slow moving electrons were copiously reflected from conducting faces. Farnsworth showed that for primary electrons having velocities less than 9 volts, most of the secondary electrons had velocities equal to the primary. As the primary potential was increased, the percentage of the reflected electrons decreased gradually but was appreciable at 110 volts. Davisson and Kunsman obtained reflected electrons even at primary potentials of 1000 and 1500 volts in the cases of some metal faces. At higher potentials we have also the electrons that undergo the Davisson and Germer scattering from the many crystal facets on the bombarded targets. As the potential is increased, the number of electrons with low velocities increases steadily and at large applied potentials, we have a large percentage of these in the secondary beam. These conclusions followed as a result of the work of Farnsworth who studied the distribution of velocities of the secondary electrons by the retarding potential method. He did not actually calculate the energy distribution from his curves but has drawn attention to the above conclusions. A careful investigation of the velocity distribution of the secondary electrons from various conducting faces was made by Rudberg at primary potentials ranging up to about 1000 volts. He adopted a magnetic deflection method similar to the one used in the analysis of the β rays and of the electrons excited by X-rays. The method had indeed been used by previous workers for the study of secondary emission, but Rudberg improved the technique considerably and obtained better focussing conditions. His results suggest that there are three groups of electrons in the secondary beam. The first group contains electrons returning with the same velocity as the primary. In the second group of electrons, we have those which undergo inelastic collisions with the orbital and structure electrons and hence are returned with some loss of energy. Richardson has drawn attention to the well-marked minimum between the two groups in Rudberg’s curves and infers that free electrons are not involved in the collisions. Finally there is the third group which contains the slow secondary electrons. The second and the third groups appear to be definitely connected with each other since they are both predominant at high primary potentials and become negligible at low primary potentials. Richardson suggests that the third group is the result of the excitation accompanying the inelastic collisions.

scholarly journals The emission of secondary electrons and the excitation of soft X-rays

1928 ◽  
Vol 119 (783) ◽  
pp. 531-542 ◽  
Keyword(s):  
Secondary Electron Emission ◽  
Good Deal ◽  
Metal Plate ◽  
Considerable Proportion ◽  
X Rays ◽  
Low Velocity ◽  
Secondary Electrons ◽  
A Value ◽  
Primary Electrons ◽  
Made In

Experiments I have recently made in collaboration with Dr. F. C. Chalklin on the one hand and with Mr. F. S. Robertson on the other, together with some observations not yet published made in the Wheatstone Laboratory by Mr. E. Rudberg, taken in conjunction with Krefft’s results for the secondary electron emission from baked tungsten, throw a good deal of light on the mechanism of the generation of secondary electrons at the surfaces of solids, particularly in the range where the energy of the primary electrons is sufficient to generate soft X-rays. I shall first consider what are the chief essential facts from this point of view as to what happens when a beam of electrons falls on a conductor. In 1908 I found that a considerable proportion of slowly moving electrons was reflected by a metal plate; in the particular case of the electrons coming from a hot platinum strip under no applied electric force on to a brass plate, I estimated the proportion reflected at roughly 30 per cent. A similar result with electrons of 2, 4 and 8 volts, equivalent energy was obtained independently about the same time by von Baeyer. Since that time a number of investigations of electron reflection at conductors have been published. Speaking broadly, it appears that with increasing energy of the primary electrons the proportion reflected, increases to a maximum, at a value which is in the neighbourhood of 11 volts for a number of metals, falls to a minimum at a value which is comparable to 30 volts, rises to a second maximum at a value which is of the order of 200 volts, and then falls off slowly and continuously with further increase in the energy. These results vary to some extent with the nature and treatment of the metal surfaces, but it is important to observe that there is generally some range of voltage in which the number of secondary exceeds the number of primary electrons. This is usually in the region in which the soft X-ray emission becomes important. Farnsworth examined the electrons emitted from a nickel plate and found that with primary electrons having 9 volts energy or less, a large proportion of the secondary electrons had an amount of energy nearly equal to that of the primary electrons, and but a small proportion had a velocity of 1 volt or less. As the energy of the primary electrons was increased above 9 volts, the proportion of low velocity electrons steadily increased and the proportion of secondary electrons having energy close to that of the primary electrons steadily fell to a very small percentage at 110 volts, a result previously obtained by Davisson and Kunsman.

scholarly journals Total secondary electron emission from a single crystal face of nickel

1930 ◽  
Vol 128 (807) ◽  
pp. 57-62 ◽  
Keyword(s):  
Single Crystal ◽  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Experimental Results ◽  
X Rays ◽  
Polycrystalline Nickel ◽  
Crystal Face ◽  
Nickel Crystal

In an accompanying paper, secondary electron experiments on ordinary nickel are described. These were conducted mainly to study the conditions of secondary electron emission and to find how far the experimental results of Retry on a polycrystalline nickel target could be reproduced. It was found that a large number of inflections were obtained some of which coincided with Petry’s values. Most of these inflections had corresponding values in Thomas’s results for soft X-rays from nickel. In this paper, the results of experiments on total secondary electron emission from the 100 face of a nickel crystal are given.

MAXIMUM SECONDARY ELECTRON YIELDS FROM SEMICONDUCTORS AND INSULATORS

2016 ◽  
Vol 24 (04) ◽  
pp. 1750045 ◽  
Author(s):  
A. G. XIE ◽  
Z. H. LIU ◽  
Y. Q. XIA ◽  
M. M. ZHU
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Maximum Yield ◽  
Secondary Electron Emission ◽  
High Energy ◽  
Secondary Electrons ◽  
Backscattered Electrons ◽  
Universal Formula ◽  
Yield Formula ◽  
Primary Electrons

Based on the processes and characteristics of secondary electron emission and the formula for the yield due to primary electrons hitting on semiconductors and insulators, the universal formula for maximum yield [Formula: see text] due to primary electrons hitting on semiconductors and insulators was deduced, where [Formula: see text] is the maximum ratio of the number of secondary electrons produced by primary electrons to the number of primary electrons. On the basis of the formulae for primary range in different energy ranges of [Formula: see text], characteristics of secondary electron emission and the deduced universal formula for [Formula: see text], the formulae for [Formula: see text] in different energy ranges of [Formula: see text] were deduced, where [Formula: see text] is the primary incident energy at which secondary electron yields from semiconductors and insulators, [Formula: see text], are maximized to maximum secondary electron yields from semiconductors and insulators, [Formula: see text]; and [Formula: see text] is the maximum ratio of the number of total secondary electrons produced by primary electrons and backscattered electrons to the number of primary electrons. According to the deduced formulae for [Formula: see text], the relationship among [Formula: see text], [Formula: see text] and high-energy back-scattering coefficient [Formula: see text], the formulae for parameters of [Formula: see text] and the experimental data as well as the formulae for [Formula: see text] in different energy ranges of [Formula: see text] as a function of [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] were deduced, where [Formula: see text] and [Formula: see text] are the original electron affinity and the width of forbidden band, respectively. The scattering of [Formula: see text] was analyzed, and calculated [Formula: see text] values were compared with the values measured experimentally. It was concluded that the deduced formulae for [Formula: see text] were found to be universal for [Formula: see text].

scholarly journals Critical potentials for the excitation of soft x-rays from iron

1930 ◽  
Vol 126 (803) ◽  
pp. 661-674 ◽  
Keyword(s):  
Velocity Distribution ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Target Surface ◽  
Photoelectric Effect ◽  
Secondary Emission ◽  
X Rays ◽  
Secondary Electrons ◽  
Current Voltage ◽  
Primary Electrons

The results of the various investigations which have been carried out during the last few years on the critical potentials for the excitation of soft X-rays, and for the production of secondary electrons, from solids, have shown that the effects occurring at solid surfaces under electronic bombardment in vacuo are more complex than was anticipated when this line of investigation was begun, and that they cannot be interpreted in any simple way in terms of the displacements of electrons within the atoms of the target. The work of various investigators* on the distribution of velocities among the electrons leaving a surface subjected to bombardment by primary electrons of known energy, has shown that a certain number of the electrons leaving the bombarded surface have energies practically equal to that of the primary stream, suggesting that a readily detectable proportion of the primary electrons is scattered or reflected at the target surface without appreciable loss of energy. The proportion of such electrons is greatest for small bombarding energies, e.g ., about 10 volts, and decreases as the voltage accelerating the primary electrons increases. The other marked feature in the velocity distribution curves, for bombarding voltages up to about 1000, is a group having a sharp maximum at about 10 volts. Apart from these features the distribution is a more or less continuous one, the number of electrons having a given velocity increasing as that velocity increases, except that after achieving a small maximum at about 25 volts less than the primary voltage, the curve falls to a minimum before rising to the very sharp peak indicating true reflection There are no indications of maxima for electron energies differing from the primary by amounts corresponding to those required to effect characteristic electron transitions within the atoms of the target. Moreover, there appears to be nothing in the velocity distribution curves for the secondary emission to correspond to the discontinuities which have been found by various investigators to occur in the current-voltage curves of the secondary electron current from a bombarded surface, or in the current-voltage curves of the photoelectric effect of the soft X-radiation excited by the bombardment. As regards the latter effect an explanation is to hand on the view that the proportion of the primary electrons whose energy is converted, in part, to photoelectrically active radiation is so small that indications of the various different energy transfers suggested by the critical potential curves are swamped in the velocity distribution curves of the secondary electrons. It is, however, more difficult to reconcile the absence of any correlation between the discontinuities which have been observed in the current-voltage curves for secondary electron emission, and the velocity distribution of the latter.

Thickness Dependence in Secondary Electron Emission from Carbon

1975 ◽  
Vol 33 ◽  
pp. 100-101
Author(s):  
D. Voreades
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Secondary Emission ◽  
Secondary Electrons ◽  
Emission Process ◽  
Backscattered Electrons ◽  
Escape Depth ◽  
Mode Of Operation ◽  
Scanning Electron

Secondary electrons are used in making topographical pictures of specimens in the scanning electron microscope. A better understanding of the secondary emission process will contribute in improving the resolution in this mode of operation.Recent experiments have indicated first that the escape depth of secondary electrons is a few atomic layers at the surface of the solid and second that the backscattered electrons are much more efficient in producing secondaries than the incoming ones. The results vary considerably. However, any model that one makes, for example similar to that of Jonker, consistent with these recent experimental results, will have the thickness as an important parameter.

Surface effects in a capacitive argon discharge in the intermediate pressure regime

2021 ◽  
Author(s):  
Jon Tomas Gudmundsson ◽  
Janez Krek ◽  
De-Qi Wen ◽  
Emi Kawamura ◽  
Michael A Lieberman
Keyword(s):  
Excited States ◽  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Plasma Sheath ◽  
Secondary Electrons ◽  
Particle In Cell ◽  
Argon Discharge ◽  
Discharge Operation ◽  
Ion Impact

Abstract One-dimensional particle-in-cell/Monte Carlo collisional (PIC/MCC) simulations are performed on a capacitive 2.54 cm gap, 1.6 Torr argon discharge driven by a sinusoidal rf current density amplitude of 50 A/m2 at 13.56 MHz. The excited argon states (metastable levels, resonance levels, and the 4p manifold) are modeled self-consistently with the particle dynamics as space- and time-varying fluids. Four cases are examined, including and neglecting excited states, and using either a fixed or energy-dependent secondary electron emission yield due to ion and/or neutral impact on the electrodes. The results for all cases show that most of the ionization occurs near the plasma-sheath interfaces, with little ionization within the plasma bulk region. Without excited states, secondary electrons emitted from the electrodes are found to play a strong role in the ionization process. When the excited states, secondary electron emission due to neutral and ion impact on the electrodes are included in the discharge model, the discharge operation transitions from α-mode to γ-mode, in which nearly all the ionization is due to secondary electrons. Excited states are very effective in producing secondary electrons, with approximately 14.7 times the contribution of ion bombardment. Electron impact of ground state argon atoms by secondary electrons contributes about 76 % of the total ionization; primary electrons, about 11 %; metastable Penning ionization, about 13 %; and multi-step ionization, about 0.3 %.

Study of Secondary Electron Emission Depended on Surface Charge of Space Insulator Materials

2014 ◽  
Vol 716-717 ◽  
pp. 137-141
Author(s):  
Na Feng ◽  
De Tian Li ◽  
Sheng Sheng Yang ◽  
Yi Feng Chen ◽  
Dao Tang Tang ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Electron Irradiation ◽  
Electron Emission ◽  
Essential Role ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Dielectric Surface ◽  
Electron Bombardment ◽  
Secondary Electrons ◽  
Surface Charging

Secondary electron emission (SEE) processes play an essential role in spacecraft surface charging. It is difficult to study SEE of insulator whose surface cumulates charges by incident electron bombardment because of poor conductivity. This paper investigated the theoretical process of generation, transfer and escape of secondary electrons, and finally the paper presented a mathematical model to calculate the secondary electron emission. We also have improved measurement system to measure total SEE coefficient from dielectric with 1-5 keV electron irradiation which is perfectly fit to mathematical model, and the SEE coefficient with different surface charging is investigated. The results indicate the SEE coefficient decreases with positive charging and increase with negative charging of dielectric surface.

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