Positive Ion Bombardment Research Articles

Depth Profiling of n‐Type Dopants in Si and GaAs Using Cs+ Bombardment Negative Secondary Ion Mass Spectrometry in Ultrahigh Vacuum

Phosphorus and arsenic ion‐implanted in silicon, and sulfur and silicon ion‐implanted in gallium arsenide have been depth‐profiled by secondary ion mass spectrometry down to concentration limits of . This was accomplished by monitoring negatively charged secondary ions produced by cesium positive ion bombardment. Contamination from the vacuum system was avoided by performing all analyses at pressures of .

Interpretation and prediction of gaseous electrical-breakdown characteristics in a crossed magnetic field

Breakdown characteristics in a crossed magnetic field are analysed with the aid of the equivalent-reduced-electric-field (e.r.e.f.) concept. Individual contributions to the secondary ionisation process can be separated, and, in argon, the contribution is mainly due to photons and/or metastable atoms; in ethane, it is wholly due to positive ions; and in hydrogen and nitrogen, a mixture of these two processes exists. For the first time, Somerville's formula for electron recapture by the cathode on account of the crossed magnetic field is shown to work, and also Haydon's suggestion that the secondary ionisation process by photons in subject to the e.r.e.f. principle is substantiated. There is evidence to suggest that secondary electrons leave the cathode under positive-ion bombardment with almost zero energy, whereas, under photon and/or metastable action, the secondary electrons are considered to have a substantial escape velocity which, it is calculated, reduces their probability of being recaptured by the cathode. The use of e.r.e.f. allows successful analysis and prediction of breakdown characteristics in a crossed magnetic field, and the whole subject is shown to be soundly based and to form a harmonious and sell-consistent topic.

The temporal behaviour of emission from excited metal atoms in the cathode region of a pulsed discharge in air

In the emission spectrum of the cathode region of a repetitive, pulsed discharge in air, lines are observed which correspond to excitation of atoms of cathode material, with a very different temporal behaviour from the N2 molecular bands which form the major part of the spectrum. It is thought that these lines are due to excitation by electron impact of metal atoms sputtered from the cathode surface by positive ion bombardment. By assuming that the structure of the cathode region is similar to that of a low pressure glow discharge, it is possible to develop a model for the temporal behaviour of the line emission in following the diffusion of the sputtered atoms through the various zones of the cathode fall and negative glow. The calculations reproduce the major features of the behaviour observed in the experiments.

A Penning source for negative hydrogen ions

A Penning source is described yielding negative hydrogen ion currents above 0.4 A and negative deuterium ion currents up to 0.2 A. Negative ions are most likely produced by positive ion and neutral atom bombardment of cesium covered surfaces. Processes in the source leading to the production and destruction of negative ions will be analyzed and possible scaling up of such sources to yield currents of several amperes will be discussed.

Energy balance at arc cathode root on copper with oxide films above 25 nm thickness

Energy-balance components are evaluated for an emitting site on a copper cathode with lOOnm-thick oxide film, and show Joule heating to be more important than positive-ion bombardment, which confirms a filamentary switching model.

Scintillation response of nonactivated and activated NaI to random and channeled ions: Influence of the luminescence mechanism

Previous experiments have shown that the scintillation response to random positive-ion bombardment of alkali iodides, both nonactivated and activated, have similar characteristics even though the luminescence mechanisms are very different. This paper reports experiments on nonactivated NaI and NaI(Tl). The relative pulse height as a function of energy for randomly incident protons (3-14 MeV) and $^{16}\mathrm{O}$ ions (5-50 MeV) for both crystals has been recorded. Also, pulse-height spectra due to energetic $^{16}\mathrm{O}$ ions (10-50 MeV) channeled along the {100} plane and $〈100〉$ axis of nonactivated NaI at 100\ifmmode^\circ\else\textdegree\fi{}K are presented and compared with those obtained previously for NaI(Tl). The following observations are made: (i) The ratio of the relative number of photons per unit energy for $^{16}\mathrm{O}$ ions to that for protons is very nearly the same for both crystals. (ii) The ratio of light outputs for totally channeled particles to random particles is nearly the same for both crystals. (iii) The detailed characteristics of pulse-height spectra from channeled ions are very similar for the two crystals. These results indicate that the scintillation response is quite insensitive to the particular luminescence mechanism.

Characteristic Time of Oxygen: Calculations and Theoretical Study

We present an equation for the characteristic time τ, through which we can calculate the formative time lag of breakdown tf more accurately than previously obtained. This equation takes into consideration both the effect of the first Townsend ionization coefficient α and the second Townsend ionization coefficient due to positiveion bombardment γi. Calculations of the characteristic time τ were carried out for oxygen, using the presented equation, at uniform field and over wide ranges of the breakdown parameters. The results obtained are presented together with a brief study. It was found that the characteristic time is independent of the electrode separation d, with an error much less than 1 percent, at constant gas pressure p and electricfield strength E, over certain ranges of d. Also it was found that the characteristic time is inversely proportional to the gas pressure raised to a constant power over a wide range of pressure, at constant percentage overvoltage and constant product of gas pressure and electrode separation. In addition, the coefficients A and B of the well-known equation of the first Townsend ionization coefficient α,α=Ap exp = (-Bp/E), are obtained.

Positive ion irradiation of CdS/Cu2S thin film solar cells

Abstract The effect of positive ion bombardment on unencapsulated CdS/Cu2S thin film solar cells has been studied using monoenergetic positive ions (of 1H, 4He, 16O, 32S, 35Cl, 40Ar, 63Cu, 84Kr, 112Cd or 132 Xe) with energies in the range 10–50 keV. The current-voltage characteristics of the cells have been analysed in terms of a five parameter model. The cell degradations produced by radiation damage have been shown to be dependent on the range of the incident particle. A reduction of the short circuit current was shown to result from damage to the cuprous sulphide layer of the cell whereas damage to the junction region was found to give rise to a reduction in the open circuit voltage. Annealing effects on radiation-degraded unencapsulated solar cells have been studied and the fractional recoveries of the cell parameters have been compared.

Secondary ion emission from metal under medium energy positive ion bombardment: Mustafa Yar Khan and Saadat Ali Khan, Proc of 11th Intern Conf on Phenom in Ioniz Gases, Prague 1973, 61

Secondary ion emission from metal under medium energy positive ion bombardment: Mustafa Yar Khan and Saadat Ali Khan, Proc of 11th Intern Conf on Phenom in Ioniz Gases, Prague 1973, 61

885. Comparison of secondary electron emission due to positron, electron and positive ion bombardment: S Pendyala and J W McGowan,Can J Phys, 52 (22), 1974, 2215–2219

885. Comparison of secondary electron emission due to positron, electron and positive ion bombardment: S Pendyala and J W McGowan,Can J Phys, 52 (22), 1974, 2215–2219

1-17 keV positive ion-induced electron ejection from tungsten, molybdenum and vanadium

Measurements have been made of secondary electron currents resulting from positive ion bombardment of clean (100) crystal targets of tungsten, molybdenum and vanadium, as well as polycrystalline tungsten, by a range of ions. Data from a relatively large number of bombarding ion species give support to Parilis and Kishinevskii's theory of kinetic electron ejection from metals (1960) and indicate the isotopic dependence of kinetic electron ejection, and that of the ejection coefficient and threshold velocities, on ion and target atom numbers.

Behavior of diamond under positive ion bombardment and CO 2 laser irradiation at very high power density

Behavior of diamond under positive ion bombardment and CO 2 laser irradiation at very high power density

Comparison of Secondary Electron Emission Due to Positron, Electron, and Positive Ion Bombardment

The relative secondary electron yield under positron, electron, and positive ion (alkali ions: Na+ or K+) bombardment is determined for the cone of a spiraltron detector (Bendix Model 4219X). The method is based on the proportionality of yield to the mean of the pulse height distribution for the bombarding particle of a given energy. The ratio of the yields under electron and positron bombardments is found to be 1.2 to 1.0 for the semiconducting lead glass of the cone of the spiraltron through the energy range of 0.1 to 1.0 keV. Cherry found this ratio to be 3.0 ± 0.3 at 0.94 keV. The positive ion yield is ≈ 1.5 (absolute) throughout this energy range.

Secondary electron emission from metals by slow positive ion bombardment

Secondary electron emission from metals by slow positive ion bombardment

Energy distribution of negative ions in hydrogen and argon positive ion bombardment of aluminium surface: J Stockel and K Jakubka, Proc 5th Czech Conf Electron Vacuum Phys, Czech Acad Sci, Brno, 1972, I a-18

Energy distribution of negative ions in hydrogen and argon positive ion bombardment of aluminium surface: J Stockel and K Jakubka, Proc 5th Czech Conf Electron Vacuum Phys, Czech Acad Sci, Brno, 1972, I a-18

An Apparatus for Study of Secondary Ions from Ion Bombardment of a Metal Surface

An apparatus for the study of secondary positive and negative ions from metal surfaces under positive ion bombardment has been constructed in stainless steel using ultra-high vacuum technology. It provides for triple mass analysis (i.e., of primary and both secondary beams), and energy analysis of the secondary ions. A retarding technique suitable for wide energy distributions has been developed. Some preliminary results obtained are given.

Thermal Behavior of a Plasma‐Heated Tungsten Probe in the Presence of Tungsten Vapor

A tungsten metal probe is heated in an argon plasma containing variable amounts of tungsten vapor. It is observed that the metal surface temperature substantially decreases when the vapor concentration increases in the gas. All other conditions being equal, the difference residing in the presence of metal vapor in the plasma, the introduction of about 0.7% vapor in the argon gas decreases the probe surface temperature by 18%, while the presence of 8% metal vapor decreases the surface temperature by 28%, the gas temperature around the probe surface being respectively 9000 and 10,000°K. An equation is found, showing the probe temperature variations in terms of the total tungsten particle concentration as well as the gas temperature immediately around the probe. A possible explanation is given for the phenomena observed which involves the existence of a protective shield of tungsten atoms and ions in equilibrium along the saturation vapor curve for tungsten. Also, the presence of solid condensed particles around the probe, with relatively low thermionic work function, may provide a protective, positively charged shield against positive ion bombardment of the probe. This interpretation is supported, to a certain extent, by the equation found.

Positive-ion bombardment of substrates in rf diode glow discharge sputtering

The plasma potential and the potential of an electrically isolated surface are measured in an rf diode sputtering glow discharge. The influence on these potentials of both the geometry enclosing the discharge volume and of a positively biased auxiliary electrode in contact with the discharge is investigated. It is shown that confining the discharge increases the plasma potential and the energy of positive ions incident on electrically isolated substrates, whereas applying a positive voltage to an auxiliary electrode also increases the plasma potential but does not significantly increase the energy of ions incident on electrically isolated substrates. The effect of rf modulation on the ionic energy distributions is demonstrated. This occurs as the ions pass through the plasma-substrate sheath and results in a large broadening of the energy distributions of low-mass species.

Secondary ionization coefficients in a low-pressure discharge in mercury vapour

Formative time lags have been measured in mercury vapour for Es/p0=138-422 V cm−1 Torr−1, and have been compared with time lags calculated from models based on Davidson's theory of the temporal growth of a gas discharge. The observed times were compatible with a model having one slow process and one faster secondary ionization process: that is, a process in which delayed photons are produced by the destruction of metastable atoms by collisions in the vapour (coefficient δ1/α), and a faster process such as positive ion bombardment (coefficient γ). The analysis could not distinguish between the various faster processes so all were included in the coefficient γ. Data are given for the appropriate values of both these secondary ionization coefficients as functions of Es/p0. The curve for δ1/α as a function of Es/p0 resembles the excitation probability curve for the 3P2 metastable state of mercury and the corresponding delayed photon process is predominant for Es/p0<220 V cm−1 Torr−1.

The dielectric breakdown of low density gases. II. Experiments on mercury vapour

It was shown in the first paper of this series that a pre-breakdown current growth equation could be developed for low pressure gases using modern computer techniques, but that a theory of breakdown presented there could not be proved conclusively because of a lack of experimental data. This paper reviews previous related experimental work on the dielectric properties of mercury vapour and describes the development of the experimental techniques necessary to obtain this data. Results of pre-breakdown current measurements are given at ( E / N ) values, an order of magnitude higher than previously reported. These allow the computation of electron multiplication by electron collision in a gap as well as secondary emission coefficients by positive ion bombardment of the cathode. It is shown that the experimental results for mercury vapour confirm the theory developed in the first paper.