Production of Kr2+ in collisions of rare gas ions with Kr

Total and differential cross sections for the production of fast Kr²⁺ ions in collisions of He⁺, Ne⁺ and Ar⁺ with Kr were measured at primary energies below 500 eV. In the system Ar⁺+Kr most of these reactions occur in close collisions and are accompanied by a large momentum transfer. For Ne⁺+ Kr collisions the angular distribution in the centre of mass system is approximately isotropic over a wide angular range. The cross section values for the Kr²⁺ production amount to 1% of the total charge transfer cross section in the investigated energy range.     

The structure of a stepped copper (410) surface determined by ion scattering spectroscopy

Ion Scattering Spectroscopy applied in the multiple scattering mode is used to determine the structure of a stepped Cu(410) surface. The energy of singly scattered ions is influenced by the presence of neighbour surface atoms. This effect can be used to determine interatomic distances up to about 10Å, as is shown by the results of 8 keV Ar⁺ and 11 keV Ne⁺ scattered through θ = 50°. The edge-edge distance of the stepped copper surface appears to be in accordance with the results of LEED experiments obtained by other investigators. The experiments show a good agreement with the results of the analytical 3-atom model of Poelsema. The energy of the so-called “plateau collision” appears to depend on the effective plateau length l as measured in the plane of incidence. Lengths l between 15 and 60 Å can be determined with an accuracy of 5 Å. Results are shown for 8 and 12 keV Ar⁺, θ = 40° and 60°, and 8 keV Kr⁺ θ = 40°. The experimental dependence of the energy on lis described correctly by a phenomenological model.     

Ion survival probabilities for 3 keV He+, Ne+, and Ar+ scattering from La and adsorbate covered La surfaces

TOF spectra of scattered neutrals and ions for 3 keV He⁺, Ne⁺, and Ar⁺ bombardment of La and adsorbate covered La surfaces show that the scattered ion fractions are 21.1% and 10.7% for Ar⁺ on clean and adsorbate covered La, respectively, and < 1% for all of the other systems. These results are consistent with a model in which Auger and resonant neutralization (AN and RN) transitions govern the ion survival probability.     

Die amorphisierung von kristallen durch ionenbeschuss und mechanismen von sekundärprozessen

Results of an experimental study of the ion-electron-emission coefficient of monocrystalline and amorphous germanium as a function of the angle of incidence for 10–30 keV Ne⁺, Ar⁺, Kr⁺ ions are presented. Using the concept of ion channeling in crystals the energy dependence of anisotropy of the ion-electron-emission coefficient is explained.     

kinetic energy reflection from polycrystals bombarded with Ar+, Kr+, and Xe+ ions

When the surface of a solid is bombarded with ions a fraction of the primary energy is reemitted by ion reflection and sputtering. The contribution of ion reflection or sputtering to energy reflection is determined by the mass ratio of the bombarding ions to the target atoms.^1,2 In the case of light ions the contribution of reflected ions is dominant. Results for He⁺ and Ne⁺ bombardment were described in a previous paper.³ The present paper deals with results for Ar⁺, Kr⁺, and Xe⁺ bombardment of the same targets as investigated before.³ The energies of the mass selected bombarding ions range from 9 to 16 keV. The measurements were carried out by means of the thermic detector described in a separate paper.⁴ For the given mass ratios most of the reemitted energy is related to sputtering.     

Ion-enhanced gas-surface chemistry: The influence of the mass of the incident ion

There are many examples of situations in which a gas-surface reaction rate is increased when the surface is simultaneously subjected to energetic particle bombardment. There are several possible mechanisms which could be involved in this radiation-enhanced gas-surface chemistry. In this study, the reaction rate of silicon, as determined from the etch yield, is measured during irradiation of the Si surface with 1 keV He⁺, Ne⁺, and Ar⁺ ions while the surface is simultaneously subjected to fluxes of XeF₂ or Cl₂ molecules. Etch yields as high as 25 Si atoms/ion are observed for XeF₂ and Ar⁺ on Si. A discussion is presented of the extent to which these results clarify the mechanisms responsible for ion-enhanced gas-surface chemistry.     

Au gettering by Ne and Ar implantation in silicon

The gettering efficiency for Au induced by Ne⁺ and Ar⁺ implantation has been studied. The depth distribution of gettered Au as a function of annealing temperature and dose of implanted Ne⁺ and Ar⁺ ions are presented. The experiment shows that the maximum efficiency of gettering occurs when the implantation doses are comparable with amorphization dose.     

Spectres auger et sections efficaces d'ionisation de la couche L23 du magnésium et de l'aluminium sous impact de protons et d'ions lourds (10–100 keV)

A comparison of Auger structures observed on the energy distributions of secondary electrons emitted from Mg and A1 solid targets bombarded by either light particles (H⁺ and He⁺) or heavy ions (Ne⁺, Ar⁺, …) is presented. With incident protons, it essentially appears a broad peak corresponding to a L₂₃VV transition and a weak shoulder due to the surface and bulk plasmon excitation. The Auger structures obtained with heavy ions are richer and the peaks which compose it are sharper. Such atomic-like structures correspond to Auger transitions from excited (with one or two L₂₃ holes) moving recoiling atoms. The experimental L₂₃ Mg and A1 ionization cross sections were determined from Auger spectra. In H⁺?Mg (or A1) collisions our results are in good agreement with the theoretical values calculated in a PWBA model. In the case of heavy ion-target interactions, we compared the experimental measurements with ionization cross section calculations obtained in a Landau-Zener model.     

Theory of ion scattering from single crystals

The scattering of He⁺, Ne⁺ and Ar⁺ ions at 600 eV from Ni(110) in the [11&#x0304;0] direction is modeled using classical dynamics. The distributions of final scattering angles of the primary ions are displayed as contour plots over the surface impact zone. From the contour plots the regions of the surface that give rise to scattering at specific angles can be isolated. The majority of the inplane scattering arises from collisions of the primary ion with second layer or “valley” atoms. However, to correctly reproduce the experimental energy distribution curves of Heiland and Taglauer (J. Vacuum Sci. Technol. 9 (1971) 620), we must include a simple collision time correction to account for neutralization of the ion beam. This analysis predicts that the ions which collide with second layer atoms of the solid are preferentially neutralized. The energy distributions due to first layer collisions agree well with experiment. We find that a full molecular three dimensional model is needed to describe all of the ion scattering events since for most of the collisions, the ion is simultaneously interacting with at least two atoms of the solid. However, in agreement with other workers we find only a single collision is responsible for the “binary” peak in the energy distribution. In addition the relative scattering intensity at different angles is dependent on having a three-dimensional solid.     

Velocity dependence of azimuthal anisotropies in ion scattering from rhodium {111}

The scattering of He⁺, Ne⁺ and Ar⁺ ions from Rh {111} is measured as a function of the azimuthal angle of the primary ion for an incident polar angle of 70° from the surface normal and an inplane collection angle of 60°. In this case anisotropy is defined as the ratio of the yield of ions scattered having the azimuth of 〈110〉 to the yield of those having the azimuth of 〈211〉. The yield ratio for all particle types correlates with particle velocity. The ratio is ～ 1 at low velocities, decreases to ～ 0.2 at 8 × 10⁶$\text{cm}\text{s}$ and then increases to a value of 1.4 at 25 × 10⁶$\text{cm}\text{s}$. Molecular dynamics calculations have been performed for Ne⁺ ion scattering from Rh{111} in order to understand the changes in anisotropy with particle velocity. Qualitative agreement with the experimental results is obtained without having to account for neutralization. A neutralization probability that depends on the collision time improves the agreement between the calculated and experimental yield ratios. A velocity dependent probability will not affect the ratio of yields in two different azimuthal directions.     

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.     

Multiple scattering and neutralization aspects of low energy noble gas ions incident on a Cu (110) crystal

Experiments have been done with 1 keV Ne⁺ ions bombarding a Cu (110) single crystal in a (111) plane. From the measured energy spectra of the scattered ions the minimum and maximum scattering angles for multiple scattering on the surface are determined. These minimum and maximum scattering angles were also calculated using a computer model. The parameters for an interatomic potential function between ion and metal atom are determined by comparison of the experimental and calculated scattering angles. A neutralization model for an energetic ion at an atomic surface is given. The reliability of this model is tested by comparison of the results of computer calculations and the measured peak intensity distributions as a function of the scattering angle.     

Inelastic energy losses in single and double collisions of keV-energy Ar<Superscript>+</Superscript> ions with Be,C, Al,Si, Ge,and in targets

Inelastic energy losses Q in scattering of Ar⁺ ions with an initial energy of E ₀ = 5 keV from Be, C, Al, Si, Ge, and In targets are determined using low-energy ion scattering spectroscopy. In spite of the fact that Ar⁺ ion beams are used in the overwhelming majority of applied studies devoted to analysis of the elemental composition and structure of materials for modern electronics, information on inelastic losses for these bombarding particles is scarce. It is shown that the knowledge of the value of Q makes it possible to correctly interpret the energy spectra of particles emitted during ion bombardment of the surface.     

Calculations of the level of primary radiation defects (displacements per atom) taking into account surface sputtering

The results of analytical estimates and computer simulations of the primary radiation damage level in the number of displacements per atom (dpa) in solids are presented and compared, taking into account the material sputtering under ion bombardment. Calculations were performed for the bombardment of carbon-based materials by Ar⁺, Ne⁺, and N⁺ ions with energies of 2?C30 keV, when considerable ion-induced changes in the material??s structure are observed. A comparison shows the close fit of the analytical and computer calculations.     

Luminescence in collisions of low-energy ions with graphite and Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

Excitation of H⁺, H₂ ⁺, H₃ ⁺, He⁺, and Ar⁺ ions by impact on graphite and Al₂O₃ was investigated by means of emission spectroscopy in the 50–1000 eV energy range of the projectiles. Emission of Balmer series from excited neutral hydrogen is observed for both targets. In addition, for the Al₂O₃ target a continuum emission is observed. The continuum probably originates from excited M_nO_m molecules produced in the collision cascade, when surface atoms bound by ionic bonds are released after the bond breaking caused by neutralization. The spectra obtained under Ar⁺ -bombardment show Ar II lines emitted by backscattered ions.     

Double scattering of ions from polycrystalline materials

In this paper double scattering of ions from polycrystalline materials has been theoretically investigated. It is shown that double collision events contribute to the yield at low energy as well as to the high energy flanks of the peaks depending on whether or not the azimuthal angle ø₁ is greater than or less than a critical angle ø_1c at a given first scattering angle θ₁. There are various combinations of first scattering angle θ₁ and second scattering angle θ₂ which give the required retained energy in two successive collisions. Scattering cross sections derived from the Bohr potential and a double interpolation sub-routine are used to calculate the scattering yield at various angles. Two systems, Ne⁺ scattered from copper and Ar⁺ scattered from gold, each at 30 keV primary energy, have been compared with experimental results.     

AES, EELS and TRIM investigation of InSb and InP compounds subjected to Ar ions bombardment

The interaction of ions with matter plays an important role in the treatment of material surfaces. In this paper we study the effect of argon ion bombardment on the InSb surface in comparison with the InP one. The Ar⁺ ions, accelerated at low energy (300 eV) lead to compositional and structural changes in InP and InSb compounds. The InP surface is more sensitive to Ar⁺ ions than that of InSb. These results are directly inferred from the qualitative Auger electron spectra (AES) and electron energy loss spectroscopy (EELS) analysis. However, these techniques alone do not allow us to determine with accuracy the disturbed depth in Ar⁺ ions of InP and InSb compounds. For this reason, we combine AES and EELS with the simulation method TRIM (transport and range of ions in matter) to show the mechanism of interaction between the ions and the InP or InSb and hence determine the disturbed depth as a function of Ar⁺ energy.     

Energy distributions of low-energy noble gas ions backscattered from a single-crystal nickel surface

The energy distribution of noble gas ions in the energy range below 1 keV from a single-crystalline surface depends on the composition and the structure of the surface, the mass and energy of the impinging ions and the geometrical conditions (e.g. angle of incidence) of the experiment. In the case of He ions the kinematic binary collision theory can be applied. For Ne ions the scattering process is more complicated, good agreement between a multiple scattering model and the experiment is achieved. Deviations from this general behaviour are observed with heavier ions (Ar⁺) and at very low energies. The experimental evidence for the different processes is discussed.     

Sputtering yields of nickel and chromium

The sputtering yield of polycrystalline nickel and chromium was determined as a function of projectile energy (1–8 keV), projectile mass (N⁺, Ne⁺, Ar⁺, Xe⁺), angle of incidence (0°–75°), and oxygen partial pressure. Where theoretical values exist, the agreement is reasonable.EURATOM Association