Secondary ion emission from Si under nitrogen ion bombardment

The yield and energy distribution of positive secondary ions emitted from Si under N₂⁺ ion bombardment were measured. The obtained mass peaks correspond to three types of secondary ion species, that is, physically sputtered ions (Si⁺, Si₂⁺), chemically sputtered ions (SiN⁺ Si₂N⁺) and doubly charged ions (Si²⁺). The dependence of secondary ion emission on the primary ion energy was studied in a range of 2.0–20.0 keV. The yields of physically and chemically sputtered ions were almost independent of the primary ion energy. The yield of the doubly charged ion strongly depended on the primary ion energy. The energy distribution of secondary ions of the three types showed the same dependence on the primary ion energy. The most probable energy of the distribution increased with the primary ion energy. On the other hand, for the energy distribution curves of sputtered ions, the tail factors N in E^?N were constant and showed a m/e dependence.     

Resistance changes in thin metallic films under ion bombardment

Resistance changes in thin films of copper, aluminium and bismuth have been studied under the bombardment of nitrogen, carbon and argon ions. Variations in resistance with implantation dose have been observed upto doses of ∼ 3 × 10¹⁷ ions/cm² for ion energies in the range 40 to 120 keV. The results are discussed in terms of desorption of gases from the film and a composite action of sputter removal of the film and its structural changes upon ion bombardment. A simple theoretical model is discussed which can qualitatively explain the experimental observations.     

A model for the impregnated cathode emission behaviour under ion bombardment

The electron current emitted by a cathode in the saturation region decrease if the cathode is exposed to ion bombardment. The change in surface coverage with barium (oxide) is used in the model to describe the current behaviour. The steady state current reached (equilibrium current) depends on the gas pressure. The experimental results can be explained in terms of the model and the parameters are determined. The temperature dependence of the barium supply rate for an S-and M-type impregnated cathode are determined.     

Cluster ion emission in the interaction of slow highly charged ions with surfaces

Cluster ion emission from a variety of surfaces upon impact of highly charged ions is investigated by time-of-flight secondary ion mass spectrometry. The yield of cluster ions as a function of cluster size for and surface follow a power law decline with exponent approaching the -2 limit of the ”equilibrium” and ”shock wave” cluster emission models. While the decline of the cluster ion emission with cluster size is an exponential decay for highly oriented pyrolytic graphite upon impact, the decline is more gradual than for impact, such that at the relative cluster yield is 1000 times higher. Received: 22 April 1997 / Revised: 29 December 1997 / Accepted: 19 January 1998     

The role of electron shells in kinetic electron emission and luminescence under ion bombardment

Abstract

PRODUCTION ET RESTAURATION DES DEFAUTS PRODUITS PAR DES ELECTRONS A BASSE TEMPERATURE DANS LE CADMIUM On a irradié du cadmium par des électrons de 3 MeV à 20°K et étudié la restauration des défauts cristallins par des mesures de résistivité électrique. On compare nos résultats à ceux obtenus auparavant par R. R. Coltman concernant du cadmium irradié par des neutrons thermiques. Les différentes hypothèses pour expliquer ?important stade III sont discutées à la lumière des résultats connus sur les défauts ?irradiation et les défauts de trempe dans le cadmium.

Cadmium samples were irradiated with 3 MeV electrons at 20°K. The defect production and subsequent recovery up to 20°K were studied by means of electrical resistivity measurements. Our results are compared with those obtained earlier by R. R. Coltman relating to irradiated cadmium with thermal neutrons. The different hypotheses, in order to explain the important stage III, are discussed in the light of the existing experimental data on irradiation defects and quenched defects in cadmium.     

Cone shape evolution under ion bombardment

The evolution of the profile of a cone developing under ion bombardment on the etch pit bottom has been investigated by computer simulation taking into account sputtering and ion-induced migration of atoms. A twofold increase in the cone apex angle is observed, which is accompanied by the appearance of kinks on its generatrix. A plateau arises on the pit bottom and a circular parapet is formed above the flat surface.     

Auger electron emission by ion bombardment of light metals

The energy distribution of secondary electrons ejected from a metallic target upon ion bombardment (Ar⁺, 10 keV) is studied with a 180° magnetic analyser, particularly in the vicinity of the Auger peaks that appear in the electron spectra of the light metals (Li, Be; Na, Mg, Al, Si). A qualitative explanation based on the correlation diagrams which described the evolution of the electronic levels during the collision of two atoms inside the target is proposed to interpret the variation of the Auger peak intensity with the atomic number of the target.     

Enhancement of the secondary ion emission induced by fast clusters

The emission yields of the secondary ions are measured by using a conventional time of flight (TOF) technique under bombardments of Mg and C₂, Ni and Si₂ with different energies, and C_n, Si_n and Ni_n (n = 1-3) with the different charge states and with energy of 1.5 MeV per atom, respectively. For the bombardments of C_n, Si_n and Ni_n, the enhancements of the secondary ion emissions increase with increasing cluster sizes and charge states. For the bombardments of Mg and C₂, Ni and Si₂, although the mass and the nuclear charges of C₂ and Si₂ are the same as or equivalent to Mg or Ni, respectively, the enhancements of the secondary ion emissions induced by the clusters of C₂ and Si₂ in a wide energy range are also clearly indicated. The instantaneous collective interaction of the cluster constituents plays an important role in the secondary ion emissions.     

Dose regularities under ion bombardment of solids

Among other parameters which influence various processes associated with ion bombardment of solids (such as sputtering, secondary electron emission, ion scattering and so on) there is “ion dose”. As the ion dose the product of ion current density (or total ion current) and time of irradiation is usually accepted. However, this definition is valid in such cases only when the time interval required for the actual experiment (or for the actual measurement) is small as compared with a certain time interval (relaxation time) which may be approximately determined as the bombarded ion penetration depth divided by the velocity of the irradiated surface motion due to target sputtering. The examination of the situations which take place in typical ion bombardment experiments (ion current densities of about 0.01–1.00 ma/cm², sputtering ratios of about 1–10 at/ion) shows that the relaxation time turns out to be of the order of some minutes to some seconds depending strongly, in particular, on the crystalline target orientation with respect to the ion beam direction. When the time interval required for the performing of the experiment exceeds considerably the relaxation time the critical ion dose must be determined as the product of ion current density and the relaxation time. In fact, the damaged layer of the irradiated target is continuously sputtered and this process prevents the accumulation of damage. Because the relaxation time is inversely proportional to the bombarding ion current density in this case the critical ion dose proves to be independent of ion current density. This peculiar fact must be taken into account in particular when the dependence of various characteristics of the ion-solid interaction process upon bombarded ion current density are analysed. When the time interval during which the measurements are performed is comparable with the relaxation time one can expect that transient characteristics must be observed. In particular they must be observed when an abrupt change of irradiated crystalline target orientation with respect to the bombarded ion beam is performed.     

Secondary ion emission under the bombardment of Si by multiply charged Si q+ ions

The spectra of secondary ion emission under the bombardment of a B-doped Si target by multiply charged Si ^q+ ions (q = 1?C5) have been studied in the energy range of 1 to 10 keV per unit of charge. A multifold increase in the yield of secondary cluster Sk _n ⁺ ions, multiply charged Si ^q/+ ion (q = 1?C3), and H⁺, C⁺, B⁺, Si₂N⁺, Si₂O⁺ is observed as the charge of the multiply charged ions increases. The increase in the yield of secondary ions with increasing charge of the multiply charged-ion charge is most significant for ions with relatively high ionization potentials.     

Photon emission from rare gas ion bombardment of metal surfaces

Metal surfaces (Mg, Cu, Zr, Mo) are bombarded with He⁺, Ne⁺ and Ar⁺ in the energy range of 400 eV to 8 keV. Radiation from scattered projectiles and sputtered target particles is observed between 200 and 700 nm. It is shown that most of the radiating particles originate from surface collisions. Auger neutralization, resonance tunneling and direct electron transitions are the important electronic processes involved.     

Computer simulation of knock-on effect under ion bombardment

A knock-on effect appearing in ion bombardment was studied from computer simulation. The preliminary results obtained for the bombardment of 4 keV Ar⁺ ion on Cu target having a random lattice are briefly described.     

Formation and decomposition of nitrides under ion bombardment

The chemical processes of formation and decomposition of narrow-gap nitrides InN and GaAs_{1 ? x} N _x under ion bombardment have been investigated by Auger electron spectroscopy. It is shown that, due to chemical instability, a large fraction of InN decomposes with formation of metal clusters under ion bombardment. It is established that bombardment of GaAs with a beam of N ₂ ⁺ and Ar⁺ ions makes it possible to obtain a chemically homogeneous GaAs_{1 ? x} N _x solid solution with a high nitrogen content (x = 0.1), whereas implantation of only N ₂ ⁺ ions leads to the formation of a mixture of GaN, GaAsN, and GaAs phases. It is concluded that secondary ion cascades, induced by heavy ions, stimulate nitridation reaction, homogenize the spatial atomic distribution, and shift the dynamic equilibrium to the formation of a single-phase solution.     

A mechanical model of amorphization under ion bombardment

A mechanical model is proposed for the amorphization of solids. The model is based on a concept according to which the accumulation of radiation-induced defects gives rise to forces and force moments that act on local volumes of the material and are responsible for fragmentation. The estimates obtained demonstrate that the proposed model can adequately describe the amorphization of solids only with allowance made for strain waves generated during reactions between defects. This model is consistent with the paracrystalline structure of silicon layers transformed into the amorphous state under ion bombardment.     

Increasing adhesion of metallic films to silicon by ion bombardment during growth

Intense ion bombardment at the initial stage of film growth is used to increase the adhesion of nickel and vanadium films to silicon. The films are deposited by rf magnetron sputtering when a bias potential is applied to a substrate. The adhesion of metallic films to silicon is substantially increased due to active mixing of the contacting materials and the formation of a transition layer with a concentration gradient. A correlation between the adhesion of the films and their crystalline state is revealed.     

Evolution of pattern formation under ion bombardment of substrate

Processes of self-organization described by a nonlinear evolution equation of sixth order are considered on substrate surfaces after ion beam bombardment. Five families of exact solutions are found for the nonlinear evolution equation. A numerical method enabling one to solve the boundary value problem is presented. Simulation of the pattern formation and classification of their profiles are given. The influence of the third, fifth order dispersion terms and a nonlinear diffusion term on processes of the pattern formation is discussed.     

A method of quantitative analysis based on ion bombardment induced secondary ion and photon emission

An absolute method of quantitative analysis using both secondary ion and photon emission is described. The method has been applied to the analysis of some NBS steel and Fe/Cr/Ni alloys, with good results. Enhancement of signal strength by means of an O⁺₂ beam or O₂ adsorption is not necessary for this method.     

Beryllium double K X-ray emission by proton and helium ion bombardment

X-ray spectra from beryllium by proton and helium ion bombardment are studied. A clear peak due to double K-shell ionization is observed at 146.1 eV by helium ion bombardment. For proton bombardment, a peak of double K-shell ionization is not observable.