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 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 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.

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].

HIGH DENSITY DIAMOND WHISKER FABRICATION AND SUPPRESSION OF SECONDARY ELECTRON EMISSION BY WHISKERS

2002 ◽  
Vol 01 (05n06) ◽  
pp. 431-436
Author(s):  
D. JEON ◽  
S. W. LEE ◽  
Y. J. BAIK
Keyword(s):  
Electron Emission ◽  
Diamond Film ◽  
Secondary Electron ◽  
Metal Clusters ◽  
Secondary Electron Emission ◽  
Narrow Gap ◽  
Secondary Electrons ◽  
Parallel Direction ◽  
Emission Yield ◽  
Primary Electrons

Diamond whiskers were formed by etching diamond thin films using metal clusters as a shadow mask, which were deposited on the diamond film before or during etching. The whiskers were as thin as 100 nm and the density was as high as 1010/ cm 2. The secondary electron emission yield of the diamond whiskers was significantly reduced as compared to the initial diamond film. The decrease in the yield was more significant if the primary electrons were impinged in parallel direction with the whiskers. We suggest that absorption of the secondary electrons in the narrow gap between the whiskers was the reason for the decreased yield.

scholarly journals The secondary electron emission from metals in the low primary energy region

1943 ◽  
Vol 182 (988) ◽  
pp. 17-47 ◽  
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Contact Potential Difference ◽  
Secondary Electron Emission ◽  
Primary Energy ◽  
Essential Elements ◽  
Contact Potential ◽  
Secondary Electrons ◽  
Average Value ◽  
Primary Electrons

This paper describes a new method and apparatus for measuring and analysing the secondary electron emission from non-gaseous materials. It has been devised especially for dealing with secondary emissions caused by primary electrons of very small energy. The essential features include a beam of primary electrons defined and controlled by an electrostatic electron lens system, which directs it towards the centre of a sphere A of the material investigated. A is surrounded by a concentric conducting sphere which collects the secondary electrons emitted from the surface of A . With the arrangement as set up it is possible to measure the contact potential difference between essential elements of the apparatus during the course of the experiments, without moving them or doing anything which would change the nature or composition of their surfaces. The method is applied to the case of pure gets-free copper with primary electrons having energies down to the lowest practicable with a tungsten thermionic source (about 0.35 eV at 2000° K). The distribution of energy is analysed both for the primary and the secondary electrons. It is found to be practically the same for both groups for all energies below a few volts. From this we deduce (1) that for these low-energy electrons the secondary electrons are just reflected electrons, and (2) that the coefficient of reflexion r varies very little with the energy of the electrons. Numerous direct determinations of r have been made. It is shown that no manipulation with fields can ever reduce the mean energy of electrons from a thermionic source below 2 kT , where T is the temperature of the source and k is Boltzmann’s constant. Many determinations of r have been made from a few volts down to 2 kT , and the average value of r is about 0.24. No variation of r has been established with certainty, but there are indications that it drops a little from the value at 2 kT to a minimum at about 2 kT + 0.5 eV, then increases slightly.

Historical Introduction

1977 ◽  
Vol 35 ◽  
pp. 2-5
Author(s):  
R. D. Heidenreich
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
50Th Anniversary ◽  
Secondary Emission ◽  
Wave Nature ◽  
Nobel Prize In Physics ◽  
Primary Electrons ◽  
The U.S ◽  
Mutual Agreement

This program has been organized by the EMSA to commensurate the 50th anniversary of the experimental verification of the wave nature of the electron. Davisson and Germer in the U.S. and Thomson and Reid in Britian accomplished this at about the same time. Their findings were published in Nature in 1927 by mutual agreement since their independent efforts had led to the same conclusion at about the same time. In 1937 Davisson and Thomson shared the Nobel Prize in physics for demonstrating the wave nature of the electron deduced in 1924 by Louis de Broglie.The Davisson experiments (1921-1927) were concerned with the angular distribution of secondary electron emission from nickel surfaces produced by 150 volt primary electrons. The motivation was the effect of secondary emission on the characteristics of vacuum tubes but significant deviations from the results expected for a corpuscular electron led to a diffraction interpretation suggested by Elasser in 1925.

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.

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