Synergetic effect between ion energy and sample temperature in the formation of distinct dot pattern on Si(1 1 0) by ion-sputter erosion

We observed a synergetic effect between ion energy and sample temperature in the formation of distinct dot pattern on Si(1 1 0) by Ar⁺ ion sputtering. The ion flux was 20 μA/cm², a value smaller than those used in preceding reports by one or two orders of magnitude. In experiments, the ion energy was from 1 to 5 keV, and the temperature from room temperature to 800 °C. A phase diagram indicating the ranges of ion energy and temperature within which distinct dot patterns can be achieved has been obtained. Data analyses and simulation results reveal that the synergetic effect is consistent with the effect of the Ehrlich-Schwoebel step-edge barrier, rather than the Bradley-Harper model.     

Effective sputtering yields of titanium,titanium nitride,and molybdenum induced by nitrogen ions and ions of nitrogen-oxygen mixtures

This work is dedicated to studying the effects of nitrogen ions and ions of nitrogen and oxygen mixtures on the surface of titanium, titanium nitride, and molybdenum. The usage of magnetron sputtering systems as a model device to study the effect of reactive gases on elements of electric jet engines is proposed and justified. The processes of sputtering of a surface exposed to non-monoenergetic ion beams are studied. The effective sputtering yields of titanium, titanium nitride, and molybdenum induced by argon and nitrogen ions and ions of nitrogen-oxygen mixtures at various intermediate-energy ion beams are determined. It is shown that the sputtering yields of reactive-gas ions are significantly lower than the sputtering yields of inert gases.     

Pt(111)表面低能溅射现象的分子动力学模拟

利用嵌入原子方法的原子间相互作用势，通过分子动力学模拟，详细研究了贵金属原子在Pt (111)表面的低能溅射现象.模拟结果显示：对于垂直入射情况，入射原子的质量对Pt (11 1)表面的溅射阈值影响不大.当入射原子的能量小于溅射阈值时，入射原子基本以沉积为主 ；当入射原子的能量大于溅射阈值时，溅射产额随入射原子能量的增加而线性增大；当入射 原子能量达到200 eV时，各种入射原子的溅射产额都达到或接近1，此时入射原子主要起溅 射作用.溅射原子发射的角分布概率和溅射花样与高能溅射相类似.研究表明：与基于二体碰 撞近似的线性级联溅射理论不同，当入射原子能量大于溅射阈值时，低能入射原子的溅射产 额正比于入射原子的约化能量和入射原子与基体原子的质量比.通过对低能入射原子的钉扎 能力分析，提出了支配低能溅射的入射原子反射物理机理. 关键词： 分子动力学模拟、低能溅射     

Systematic investigation of the reactive ion beam sputter deposition process of SiO<Subscript>2</Subscript>

Ion beam sputter deposition (IBSD) is an established physical vapour deposition technique that offers the opportunity to tailor the properties of film-forming particles and, consequently, film properties. This is because of two reasons: (i) ion generation and acceleration (ion source), sputtering (target) and film deposition (substrate) are locally separated. (ii) The angular and energy distribution of sputtered target atoms and scattered primary particles depend on ion incidence angle, ion energy, and ion species. Ion beam sputtering of a Si target in a reactive oxygen atmosphere was used to grow SiO₂ films on silicon substrates. The sputtering geometry, ion energy and ion species were varied systematically and their influence on film properties was investigated. The SiO₂ films are amorphous. The growth rate increases with increasing ion energy and ion incidence angle. Thickness, index of refraction, stoichiometry, mass density and surface roughness show a strong correlation with the sputtering geometry. A considerable amount of primary inert gas particles is found in the deposited films. The primary ion species also has an impact on the film properties, whereas the influence of the ion energy is rather small.     

Sputtering of boron nitride single crystals of different structure

Results obtained in studying the sputtering of single crystals of hexagonal, rhombohedral, and cubic boron nitride modifications by computer simulations are reported. Data on sputtering the (0001) face of BN in two graphite-like modifications and the (111) face of BN crystals with a cubic lattice are presented. The energy and angular dependences of the sputtering yields and spatial and energy distributions of sputtered particles are considered for the cases of normal and oblique ion incidence. Specific features of the anisotropy of spatial distributions of sputtered particles and mechanisms of their formations are analyzed.     

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.     

Simulation of boron nitride sputtering process and its comparisonwith experimental data

In the paper, TRIM and TRIDYN simulation codes were used to simulate the sputtering processes of boron nitride (BN) films during bombardment of ions. The TRIM and TRIDYN codes are applicable to the simulation of sputtering processes of different target materials with amorphous and polycrystalline structure. The results of the simulations are compared with experimental data. The sputtering experiments of polycrystalline hexagonal BN (h-BN) and cubic BN (c-BN) films were performed in a Commonwealth Scientific Corporation (CSC) 38-cm ion beam source device. The comparison of calculated and experimental results indicated that a) the experimental sputtering yields of h-BN and c-BN films bombarded with Ar⁺ ions versus the angle of incidence are in reasonable agreement with the calculated results; b) the sputtering yields of h-BN and c-BN bombarded with Ar⁺ are nearly of the same values versus the angle of incidence-preferential sputtering of h-BN was not found; c) the calculated sputtering. Yields of BN as a function of Ar⁺ ion energy are very sensitive to values of the surface binding energy (SEE); and d) surface binding energy between 2 and 3 eV for BN appears to be reasonable for the simulation of sputtering process of h-BN and c-BN films     

Secondary Ion Mass Spectrometry Imaging

Secondary ion mass spectrometry (SIMS) is a chemical analysis technique that employs mass spectrometry to analyze solid and low volatility liquid samples [1]. Although there are numerous configurations of SIMS instrumentation, the fundamental basis of SIMS analyses is the measurement of the mass and intensity of secondary ions produced in a vacuum by sputtering the surface of the sample with energetic ion or neutral beams. The sputtering beam is referred to as the primary beam and typically has a kinetic energy of several thousand electronvolts (keV). The primary beam removes atomic or molecular layers at a rate determined principally by the intensity, mass, and energy of the primary species and the chemical and physical characteristics of the sample [2]. Particle sputtering at the kiloelectronvolt level produces a variety of products including electrons, photons, atoms, atomic clusters, intact molecules, and distinctive molecular fragments. A small fraction of these sputter products are ionized, and these ions are the secondary ions in secondary ion mass spectrometry.     

Preferred sputtering on binary alloy surfaces of the AlPdSi system

Auger spectroscopy has been used to investigate the behavior of preferred sputtering on surfaces of homogeneous AlPd, SiPd and AlSi alloy films. These combinations of alloys were chosen for studying the effects of mass and bonding differences on preferred sputtering. Experiments have been carried out using a 1 keV Ar ion beam over a range of alloy compositions. Our results can be summarized as follows: (a) The preferred sputtering of these binary alloys cannot be predicted according to the sputter yields of individual elements, e.g. both Al and Si have been observed to be removed preferentially relative to Pd although pure Pd has a higher sputter yield, (b) In the alloys studied, mass difference appears to dominate over bonding difference in controlling the preferred sputtering behavior since the extent of preferred sputtering of Al and Si relative to Pd is about the same. This observation is interpreted on the basis of the binary alloy sputtering theory formulated by Andersen and Sigmund. (c) Judging from the composition change of the sputtered surface, there is no evidence for formation of compounds with specific compositions as a result of preferred sputtering in the AlPd and SiPd alloys investigated.     

Extremely low-energy projectiles for SIMS using size-selected gas cluster ions

A new cluster time-of-flight secondary ion mass spectrometry (TOF-SIMS) was developed using a size-selected gas cluster ion as a projectile. Since a large gas cluster ion can generate many low-energy constituent atoms in a collision with the surface, it causes multiple and ultra low-energy sputtering. The mean kinetic energy of constituent atoms is provided by dividing the acceleration energy of the gas cluster ion by the number of constituent atoms. Therefore, the sputtering can be controlled to minimize the decomposition of sample molecules and substrate material by precisely adjusting the number of constituent atoms (the cluster size) and/or acceleration energy of the gas cluster ion. The cluster size was selected on the basis of the time-of-flight method using two ion deflectors attached along the ion-beam line. A high resolution of 11.7 was achieved for the cluster size/size width (M/ΔM) of Ar-cluster ions.     

Photon-induced sputtering

Photon induced sputtering occurs in many materials. It is different from ion beam sputtering because the photon beam lacks momentum and this must always be derived from a secondary process. In general the result is an emission of atoms with approximately thermal energy. However processes do exist which can produce more energetic sputtering and also the directional effects associated with replacement collision sequences within the lattice. The general principles for photon induced sputtering are reviewed.     

Isotope effects induced by the action of ions on the surface of solids

We report on the results of study of isotope effects induced in solids by ion sputtering and ion implantation. The experiments are carried out using secondary ion mass spectrometry and secondary ion energy-mass spectrometry on molybdenum and copper-implanted nickel samples, as well as a number of titanium modifications. General regularities are revealed in the variation of the isotope composition in various processes. The mechanisms of isotope effects are discussed.     

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依据钨材料表面溅射的实验现象,建立钨材料表面粗糙模型,模拟了高能H+、He+粒子辐照下的钨材料表面的溅射行为过程,并与基于离子输运的双群模型计算得到的结果作了比较。结果表明,随着钨材料表面粗糙程度的增加,溅射率降低;对一定的粗糙表面,相同能量的不同入射粒子,质量越大粒子溅射率越高,这些结果为分析聚变装置中心等离子体杂质水平和评价偏滤器寿命等提供了一定的理论支撑。     

Sputtering—a review of some recent experimental and theoretical aspects

After a brief outline of the present sputtering theory for a random solid, recent results of the sputtering yieldS for polycrystalline targets are discussed, in particular in view of the influence of the projectile mass and the bombarding angle. The angle dependence ofS at low bombarding energies, and results on the angular distribution of sputtered particles for oblique ion incidence point out necessary modifications of present sputtering theories with respect to the anisotropy of the collision cascades in the solid and the influence of the target surface. The energy distribution of the neutral particles ejected along the target normals is related to the theoretically predictedE ^?2-distribution of low energy recoils in the Recent mass spectrometric studies of postionized sputtered neutrals are discussed in view of the formation of sputtered molecules and the application of sputtered neutral mass spectroscopy for surface analysis. Finally, the paper deals with ion-induced surface effects on non-elementary sputtering targets, and the protracted removal of foreign atoms from a matrix.     

Ion beam sputter deposition of TiO<Subscript>2</Subscript> films using oxygen ions

TiO₂ thin films were grown by ion beam sputter deposition (IBSD) using oxygen ions, with the ion energy and geometrical parameters (ion incidence angle, polar emission angle, and scattering angle) being varied systematically. Metallic Ti and ceramic TiO₂ served as target materials. The thin films were characterized concerning thickness, growth rate, surface topography, structural properties, mass density, and optical properties. It was found that the scattering geometry has the main impact on the film properties. Target material, ion energy, and ion incidence angle have only a marginal influence. Former studies on reactive IBSD of TiO₂ using Ar and Xe ions reported equivalent patterns. Nevertheless, the respective ion species distinctively affects the film properties. For instance, mass density and the refractive index of the TiO₂ thin films are remarkably lower for sputtering with oxygen ions than for sputtering with Ar or Xe ions. The variations in the thin film properties are tentatively attributed to the angular and the energy distribution of the film-forming particles, especially, to those of the backscattered primary particles.     

离子引出收集的沉积与溅射研究

研究离子引发收集过程中的沉积和溅射特性,给出了离子沉积和溅射的数理模型,其中重点分析了结合能、捕获概率和溅射系数这几个参数的物理意义和计算公式,给出了收集板总收集量和损失量.并且用计算机模拟了收集板的收集,给出不同的离子入射能量下入射离子元素沉积厚度和不同元素靶对各入射离子溅射特性的影响.得出以下的结论:随着离子沉积在收集板表面涂层厚度的增加溅射率也增加;离子的引出电压不是越高越好;轻质量离子的总收集率比较小;入射离子沉积和溅射特性和收集板靶原子质量有关,质量轻的金属材料作收集板,有利于提高离子的收集率. 关键词： 溅射 捕获概率 溅射概率     

Precise atomic scale studies of material sputtering by light-ion gases in the prethreshold energy region

The basis and prospects of a new original technique of determining the yields of the sputtering of conductive materials and subatomic films on their surface by light ion gases in the prethreshold energy region (from 10 to 500 eV) are discussed. This information is of great importance both for science and applications. The technique is based on special modes of field ion microscopy and includes the cleaning of specimens by field-induced desorption and evaporation, and subsequent operations with the atomically clean and atomically smooth surface in a wide temperature range from cryogenic temperatures. The technique enables one to identify single surface vacancies, that is, to directly count single sputtered atoms. The original results obtained with the developed technique are briefly reviewed. The energy thresholds of sputtering and the energy dependences of the sputtering yields in the prethreshold energy region are presented and analyzed for beryllium, tungsten, tungsten oxide, mixed tungsten-carbon layers, three carbon materials, and subatomic carbon films on the surface of certain metals bombarded by hydrogen, deuterium, and/or helium ions.     

Surface cleaning using sputtering

In this article sputtering phenomena as related to the removal of contaminant layers from surfaces are reviewed. Basic relations for sputtering of adsorbed layers by ion bombardment and the corresponding cross sections are discussed in the introductory part. The following section presents models for the sputtering of overlayers with the intention of understanding the relevant physical processes and to obtain quantitative estimates. Subsequently, undesirable by-products of ion bombardment, such as surface damage, particle implantation and preferential sputtering are considered. A concise experimental section deals with ion beam and glow discharge techniques applied for surface cleaning as well as with some surface analytical methods (Auger electron spectroscopy, low-energy ion scattering, secondary ion mass spectroscopy) which are useful and necessary to check the obtained cleaning effect. In the final section various examples are given and some conclusions are drawn for the efficiency of surface cleaning by sputtering.     

表面粗糙度对面向等离子体钨材料溅射的影响

依据钨材料表面溅射的实验现象,建立钨材料表面粗糙模型,模拟了高能H⁺、He⁺粒子辐照下的钨材料表面的溅射行为过程,并与基于离子输运的双群模型计算得到的结果作了比较。结果表明,随着钨材料表面粗糙程度的增加,溅射率降低;对一定的粗糙表面,相同能量的不同入射粒子,质量越大粒子溅射率越高,这些结果为分析聚变装置中心等离子体杂质水平和评价偏滤器寿命等提供了一定的理论支撑。     

Sputtering yields of PMMA films bombarded by keV C60 ions

A quartz crystal microbalance (QCM) has been used to determine total-mass sputtering yields of PMMA films by 1-16 keV C₆₀^+,2+ ion beams. Quantitative sputtering yields for PMMA are presented as mass loss per incident ion Y_m. Mass-lost rate QCM data show that a 13 keV C₆₀ cluster leads to emission equivalent to 800 PMMA molecules per ion. The power law obtained for the increase in sputtering yield with primary ion energy is in good agreement those predicted by “thermal spike” regime and MD models, when crater sizes are used to estimate sputtering.