Die Zerstäubung von Kupfer durch Ne+-, Ar+-, Kr+- und Xe+-Ionen im Energiebereich von 75keV bis 1MeV

Using a 1,3 MeV Van de Graaff-accelerator the sputtering ratioS of polycristalline copper bombarded by normally incident Ne⁺-, Ar⁺-, Kr⁺-, and Xe⁺-ions was measured in the energy range from 75 keV to 1 MeV. In the case of Kr⁺-ions a broad, plateau-like maximum of the sputtering-curveS=f(E) was found at about 100 keV, for Xe⁺-ions a more pronounced maximum at about 125 keV. The results are discussed applying the theories ofGoldman-Simon, Pease, andMartynenko.     

Spatial distribution, build-up, and annealing of radiation defects in silicon implanted by high-energy krypton and xenon ions

An x-ray diffraction study of defect formation in silicon irradiated by Kr⁺ (210 MeV, 8×10¹²−3×10¹⁴ cm⁻²) and Xe⁺ (5.6 BeV, 5×10¹¹−5×10¹³ cm⁻²) ions is reported. It has been established that irradiation produces a defect structure in the bulk of silicon, which consists of ion tracks whose density of material is lower than that of the host. The specific features of defect formation are discussed taking into account the channeling of part of the ions along the previously formed tracks and the dominant role of electron losses suffered by the high-energy ions. It is shown that the efficiency of incorporation of stable defects by irradiation with high-energy ions is lower than that reached by implanting medium-mass ions with energies of a few hundred keV. Fiz. Tverd. Tela (St. Petersburg) 40, 1627–1630 (September 1998)     

Die ZerstÄubung von Kupfer durch Edelgas-Ionen im Energiebereich von 100 keV bis 1 MeV als Funktion des Einfallswinkels

Using a 1.3MeV Van de Graaff-accelerator the sputtering ratioS of polycristalline copper bombarded by Ne⁺-, Ar⁺-, Kr⁺- and Xe⁺-ions was measured as a function of the angle of incidence in the range from 0? to 45?. The ion-energy was varied from 100 keV to 1 MeV. The sputtering ratio was found to increase with bombarding angle asS=S(0?)· (2- cos α)/cos α for Ne⁺-, Ar⁺- and Kr⁺-ions and asS=S(0?)/cos^3/2 α for Xe⁺-ions. The increase of the sputtering ratio was found to be independent of the ion-energy.     

Sputtering experiments with silver single crystals and the channeling phenomena

Sputtering yields of monocrystalline silver under irradiation with 7-30 keV Ar⁺, Kr⁺ and Xe⁺ ions, not reported earlier, have been determined. The yield has been found to depend strongly on the orientation of the crystal and mass of the impinging ion. Onderdelinden's model based on Lindhard's theory of Channeling is found to describe satisfactorily, the observed orientation and ion-mass dependence of the yields for the ions of energy ～10 keV or above. The role of the barrier potential approximated in the model in predicting the experimental results is discussed.     

Modification of the Al<Subscript>2</Subscript>O<Subscript>3</Subscript> surface by high-energy bismuth ions

This paper reports on an atomic-force microscopy study of the surface of α-Al₂O₃ single crystals irradiated by Bi ions with energies of 710, 557, 269, and 151 MeV. The shape of the radiation defects produced by single ions was established to depend on the ionization energy loss. The threshold ionization density above which the surface topography is observed to change lies in the 27–35 keV/nm interval. Possible mechanisms of defect formation in the thermal-spike model, namely, a phase transition and the creation of thermoelastic stresses in the high-energy ion track, are considered.     

氢离子注入对硅单晶电子辐照缺陷和氢泡形成的影响

以50keV和100keV能量的氢离子注入p型(100)直拉硅单晶薄膜。注入剂量为10¹⁵—2×10¹⁷H⁺/cm²。试样在HU-1300型超高压透射电子显微镜中进行电子辐照和原位加热动态观察。结果表明在20—300℃温度范围内与未注氢硅相比,注氢硅在相同的电子辐照条件下产生的电子辐照缺陷较少,电子辐照缺陷形成所需的潜伏时间较长。在电子显微镜中加热试样时于190℃开始观察到氢泡,190—220℃范围内氢泡逐渐产生并长大 关键词：     

Excitation-autoionization cross sections and rate coefficients for Ga-like ions

Detailed level-by-level calculations of cross sections and rate coefficients for electron impact direct and indirect ionization of ions belonging to the GaI isoelectronic sequence (ground 3d ¹⁰4s ²4p) have been performed. The cross sections are presented in the energy range near the threshold for the five ions Kr⁵⁺, Mo¹¹⁺, Xe²³⁺, Pr²⁸⁺ and Dy³⁵⁺. The rate coefficients are given for ions from Kr⁵⁺ to U⁶¹⁺ in the GaI sequence at seven electron temperatures (kT _e = 0.1E _I , 0.3E _I , 0.5E _I , 0.7E _I ,E _I , 2E _I and 10E _I , where E _I is the first ionization energy). The calculations include the contribution of direct ionization (DI) calculated using the Lotz formula approximation and the contributions of excitation-autoionization (EA) computed in the framework of the distorted wave (DW) approximation for the 4s-nl, 3d-nl and 3p-nl resonant inner-shell excitations. The ionization enhancement due to the EA channels is presented as a function of Z along the GaI isoelectronic sequence. The present results show the great importance of the EA processes; an ionization enhancement factor of up to 10 is predicted for instance for La²⁶⁺ (Z = 57) at electron temperature of coronal equilibrium maximum abundance.     

Independent electron theory of multiple ionization of xenon by intense laser pulses

The intensity dependence of the multiphoton ionization spectra of Xe atoms has been investigated with an improved accuracy and well-controlled laser parameters. In particular, we have examined the ionization rates for X³⁺, X²⁻, X⁺ as functions of the laser intensity and the pressure in the target chamber. The apparatus used for these measurements is characterized by a high-energy resolution (better than 200 meV) and a completely digital acquisition system. The time-of-flight spectra clearly show the contributions of the different isotopes present in Xe gas. The laser pulses have been characterized with great accuracy by monitoring the energy, pulse width and divergence shot by shot. The ionization rates of the different ions have been used for testing the basic assumption of the Geltman theory of multiple ionization based on the single electron ionization model. We have found that for the small intensity range investigated the quantity (dXe ⁺/dI)·(dXe ³⁺/dI)/(dXe ²⁺/dI)² appears to be quite close to the value 0.5 predicted by this model.     

Local magnetic order in silicon implanted with high-energy ions

A room-temperature local magnetic order has been detected in silicon implanted with high-energy Kr⁺ and Xe⁺ ions. The evidence of the presence of the local magnetic order are the electron magnetic resonance lines with g-factor values of about 2.2 and 3.4, the hysteresis of the resonance magnetic field values of these lines, the anisotropy characteristic of ferromagnets, and the broadening. The ordering effect is retained after the annealing of samples at temperatures of no higher than 1270 K.     

Experimental preparation of the initial state of Xe+-N laser-induced collisional charge transfer system: Multi-photon resonant ionization of xenon

A novel one-color Xe⁺-N laser induced collisional charge transfer system is proposed, and preparation of the initial state of the system, i.e., Xe⁺ is experimentally implemented through resonance enhanced multi-photon ionization (REMPI) by ～440 nm dye laser. The REMPI of Xe is experimentally investigated through time-of-flight (TOF) mass spectrometry and the intensity dependence of Xe⁺ is obtained, aiming at the preparation of Xe⁺. The resonant ionization spectra of Xe at ～440 nm under several different conditions are measured, showing the impacts of mode purification and source pressure on the resonant ionization spectrum. The results indicate the feasibility of preparing the initial state of the Xe⁺-N system by ～440 nm multi-photon resonant ionization, which prepares for a further experiment of laser-induced collisional charge transfer.     

Selective X-ray generation by heavy ions (Part 2) measurement of the concentration distribution of ion-implanted antimony in silicon by the use of selective heavy ion X-ray excitation

This investigation demonstrates how the total, concentration distribution of antimony, previously implanted into silicon at 100 keV, may be elucidated without recourse to the usual radioactive isotope techniques. It uses the fact that 100 keV Kr⁺ ions can preferentially excite characteristic X-rays from antimony, even in the presence of a huge excess of silicon. The resultant high sensitivity for the detection of antimony in silicon is accompanied by the fact that the X-rays arise predominantly from less than one hundred Angstroms below the surface of the specimen. Thus bombardment by 100 keV Kr⁺ íons is used ín conjunction with an anodic stripping technique (which removes 169±20 Å at a time) to obtain the antimony distribution profile in silicon. Consideration is also given to the possibility of obtaining the implanted antimony range distribution by using 100 keV Kr⁺ ions to detect the antimony and simultaneously remove silicon by sputtering.     

Energy distribution of photoelectrons generated from highly charged ions in a circularly polarized intense laser field

We observed the energy distribution of the photoelectrons generated from the highly charged ions in the tunneling regime by using a circularly polarized Ti:Sapphire laser (745 nm, 100 fs). The peaks for each successive charge state up to Ar³⁺, Kr⁴⁺, and Xe⁵⁺ were clearly resolved, and the peaks due to higher charge states were flattened in the high-energy region and deviated from those predicted by the quasistatic model. This deviation is explained by pondero-motive acceleration in the strong field gradient. In Xe, Xe⁸⁺ was generated at a peak intensity of 2.0 × 10¹⁶ W/cm².     

The influence of implanted xenon on the sputtering yield of silicon

Following implantation labeling with either 200 or 270 keV Xe⁺ the sputtering yield of silicon bombarded with 20 keV Xe⁺ has been determined in situ by means of the backscattering technique (Y = 3.0 ± 0.3 (atoms/ion)). Yield enhancement by up to 60% was observed in cases where the implantation-induced xenon concentrations exceeded the saturation concentration during sputtering. The effect is attributed to (i) an increase in energy deposition at the surface introduced by pronounced xenon loading of the target and (ii) lowering of the surface binding energy. As a consequence the energy dependence of the xenon sputtering yield of silicon is expected to be strongly affected by the energy dependence of the xenon saturation concentration in silicon. Available experimental data support this idea.     

Projectile charge and velocity effect on UO2 sputtering in the nuclear stopping regime

Angular distributions and yields of uranium sputtered by slow highly charged Xe^q+ ions (kinetic energy 1.5 keV ￡ E_k ￡ 811.5~{\rm keV}\le E_{k}\le 81  keV, charge state 1≤q≤25) from UO₂ were measured by means of the catcher technique. A charge state effect on the sputtering process is observed at 8 and 81 keV. A deviation from a Acosθ shape (the linear collision cascade theory) is observed in case of Xe^q+ impinging a UO₂ surface at E_k=8 keV. Yields increase linearly with projectile charge state q thus clearly revealing the contribution of potential energy to the sputtering process. In addition, as the kinetic energy of a Xe¹⁰⁺ projectile decreases from 81 keV to 1.5 keV, a velocity effect is clearly observed on the angular distribution.     

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.     

Dependences of HTS tape critical parameters on fluences under irradiation with heavy ions and high energy electrons

Experimental data on the study of modifications of two types of the YBCO(123)-based composite tape under irradiation with electrons with the energy of 23 MeV and ¹³²Xe²⁷⁺ (167 MeV), ⁸⁴Kr¹⁷⁺ (107 MeV), and ⁴⁰Ar⁸⁺ (48 MeV) ions in a wide range of irradiation doses are presented. It is shown that no changes in the HTS transition temperature and critical current occurred under electron irradiation up to the dose D ≈ 10⁻⁴ disp/a (displacements per atom). The threshold dose of irradiation with ¹³²Xe²⁷⁺ ions, at which superconductivity disappears, is determined. In comparison with the initial value, the critical current of ⁴⁰Ar⁸⁺ ions is found to increase by ≈18% in the zero magnetic field at T = 77 K. This effect can be explained by the pinning centers for Abrikosov vortices induced by relatively small ion irradiation doses. High doses of heavy ions lead to partial or complete amorphization of a superconductor, which results first in a decrease in the critical current and transition temperature and then in a total disappearance of superconductivity. X-ray diffraction is used to study the changes in the crystal structure of the YBCO(123) superconductor under ion irradiation.     

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.     

MeV重离子在固体靶中的平均投影射程计算

根据Biersack角扩散模型,建立了计算MeV重离子在固体靶中的平均投影射程的方法。与新近发表的1.0MeV的In⁺,Xe⁺,Ta⁺和1.0—2.0MeV的Pb⁺在Si中的平均投影射程实验数据相比,本文计算值与实验值的最大偏离为8％,而Monte-Carlo(TRIM′86)和PRAL的计算值与实验值的最大偏离分别为23％和22％。这表明本文的计算在预言1.0—2.0MeV的重离子(In⁺,Xe 关键词：     

Blistering of rhenium irradiated with 21keV helium ions

This paper describes blistering of rhenium following 21 keV He⁺-ion irradiation at temperatures between 300 K and 1200 K. Blistering starts at 300 K at a dose of 3×10¹⁷ ions/cm². The most probable blister diameter varies from 4400 ? at 300 K to 10100 ? at 1200 K. The blister depth τ _bl , the blister diameter φ _bl and the blister heighth _bi show a distribution. From the observations one could derive the following relationships:h _bl = 0.35φ _bl ; τ _bl =3.43φ _bl ^2/3 . The erosion yieldE _y due to blistering is function of doseE _y =0.51 atoms/ion at 3×10¹⁷ ions/cm²,E _y =0.56 atoms/ion at 6×10¹⁷ ions/cm² andE _y =0.14 atoms/ion at 3×10¹⁸ ions/cm². The sputtering yieldS (21 keV) is estimated to be ∼0.1 atom/ion. The corresponding surface regression is 44? at 3×10¹⁷ ions/cm² and 1323 ? at 9×10¹⁸ ions/cm². Surface regression has therefore little influence on the observations at low doses. Work performed at the Mathematicals Science Department of S.C.K./C.E.N. at Mol (Belgium)