Surface-compositional and Angular Distributions duringCu-Pt Sputtering

Under 1 keV Ar ion bombardment of Cu-Pt alloys at high fluence and low temperature, the depletion degree of the segregating species at the second surface layer, and the normalized sputtering yield ratios (non-segregating species/segregating species) in the near-normal direction (15°) and at oblique angle (75°), have been estimated by an improved kinetic BIGS (bombardment-induced Gibbsian segregation) model. For the bombarded Cu-Pt alloys, calculations show that the depletion degree of the segregating species at the second surface layer is small when its bulk composition equals the extreme value, but this depletion degree becomes large when its bulk composition equals the intermediate value. Furthermore, the difference of the normalized sputtering yield ratio between 15° and 75° is small when the buIk composition of the segregating species equals the extreme value, but this difference becomes large when that of the segregating species equals the intermediate value.     

Auger electron spectroscopy study of the sputtering effect on platinum silicide surfaces

Modifications of platinum silicides in the composition range between Pt₃Si and PtSi induced by argon ion beams were studied by angle-integrated Auger electron spectroscopy (AES). A platinum surface enrichment, which was stronger at low sputtering energies and in silicon-rich silicides, was found in the 1–5 keV ion energy range. In all silicides sputtering yield ratios Y_Si/Y_Pt of about 2.9 and 2.1 were estimated for the 1 keV and 5 keV steady state regimes respectively. Simultaneous analysis of low and high energy platinum and silicon Auger lines indicated that the platinum enrichment extended over a range of a few tens of ångströms and was slightly higher at the surface than in the subsurface region. The platinum enrichment, its energy dependence and the in-depth graded composition of the altered layer are discussed in terms of silicon preferential sputtering, recoil implantation and surface segregation. Dynamic surface composition changes were also studied, and a model which accounts for the various “shapes” of the transient regimes and their dependence on the height of the steps in the sputtering energy is shown schematically. Shape analysis of the core-valence-valence Auger lines suggests that changes in the chemical bonding in platinum silicides are induced by ion bombardment so that enrichment with platinum results in the formation of compounds which are richer in platinum.     

表面成分AES和XPS定量分析中的离子溅射修正

低能离子溅射是表面分析中清洁固体表面和深度剖面分析的主要手段之一。由于离子溅射改变了固体表面化学成分，引起表面成分的再分布，使俄歇电子谱、X射线光电子谱以及二次离子质谱等表面分析手段，对溅射后固体表面成分的定量分析结果与实际结果有较大的差别。本文以离子溅射合金表面成分达到平行时择优溅射、离子轰击诱导偏析和增强扩散效应之间动态平衡状态的假设为基础，得到了一个与择优溅射、离子轰击诱导偏析和增强扩散修正因子有关的离子溅射修正因子的分析表达式，并将其应用于Ag－Pd合金的离子溅射定量修正计算，发现计算结果能够与实验结果较好地吻合。解释了合金离子溅射修正因子随离子参数的变化。     

The effects of pre-implantation of steel substrates on the structural properties of TiN coatings

We have studied the effects of nitrogen pre-implantation of AISI C1045 steel substrates on the microstructure and microhardness of deposited TiN coatings. The substrates were implanted at 40 keV, to the fluences from 5 × 10¹⁶ to 5 × 10¹⁷ ions/cm², which was followed by deposition of 1.3-μm thick TiN coatings by reactive sputtering. Structural characterization of the samples was performed by standard and grazing incidence X-ray diffraction analysis, Rutherford backscattering spectroscopy and transmission electron microscopy. Microhardness was measured by the Vicker’s method. Nitrogen implantation up to 2 × 10¹⁷ ions/cm² induces the formation of Fe₂N phase in the near surface region of the substrates, which becomes more pronounced for higher fluences. Microstructure of the deposited TiN coatings shows a strong dependence on ion beam pre-treatment of the substrates. The layers grown on non-implanted substrates have a (200) TiN preferential orientation, and those grown on implanted substrates have (111) TiN preferential orientation. The change in preferred orientation of the layers is assigned to a developed surface topography of the substrates induced by ion implantation, and possible effects of distorted and altered crystalline structure at the surface. Ion implantation and deposition of TiN coatings induce an increase of microhardness of this low performance steel for more than eight times.     

Optical evidence for reactive processes when embedding Cu nanoparticles in Al(2)O(3) by pulsed laser deposition

The optical response of nanocomposite thin films formed by Cu nanoparticles (NPs) embedded in amorphous aluminium oxide (Al(2)O(3)) prepared by pulsed laser deposition (PLD) in vacuum is studied in order to investigate the possible existence of reactive processes on the Cu NPs during their covering with Al(2)O(3). The study is performed as a function of the laser fluence on the Al(2)O(3) target (0.6-4.6?J?cm(-2)), while the laser fluence for Cu ablation is kept constant (1.8?J?cm(-2)). The structural analysis of the films shows that they are formed by a high density of NPs with average dimensions in the 4.9-5.9?nm range. The optical response of the films has been followed in situ by real-time reflectivity measurements at 633?nm and after deposition by transmission measurements as a function of wavelength around the surface plasmon resonance (SPR). For low laser fluences on the Al(2)O(3) target, the absorption spectrum is dominated by a well-defined SPR absorption band at 1.9?eV. As the laser fluence is increased, the intensity of the absorption band associated with the SPR decreases and shifts to 2.1?eV. The films deposited at low fluences contain metallic Cu NPs and, as the laser fluence increases sputtering of Cu from the NPs and mixing of the species from the Al(2)O(3) deposition with the Cu from the NPs surface takes place. The latter process leads to the formation of an Al-Cu oxide cover on the Cu NPs. The present results provide evidence for mixing of species from the host and Cu at the surface of the NPs, and it is shown how the degree of mixing depends on the laser fluence used to ablate the Al(2)O(3) host target.     

The influence of sputtering on FeSi

The effect of different (0.5, 2 and 4 keV) Ar⁺ energy ions on (a) the composition of an FeSi surface, (b) the oxidation of the FeSi surface after bombardment, and (c) the segregation of silicon after bombardment, has been monitored by Auger electron spectroscopy. Silicon was found to be preferentially sputtered by the Ar⁺ ions at all the different energies during bombardment. This effect was more pronounced at the 0.5 keV ion energy bombardment. There was a slight increase in the oxidation rate from the higher to the lower Ar⁺ ion energy at which the sample was sputtered before oxidation. The rate of silicon diffusion to the surface at 593 K after the sample had been sputtered, was lower when the sample had been sputtered by 0.5 keV ions than by 2 keV ions.     

Surface segregation and preferential sputtering in thin Al–Ni alloy films

The surface composition of Al_xNi_1−x alloy films was studied by X-ray electron spectroscopy (XPS) after various surface treatments and oxidation at room temperature. Ion etching caused a marked enrichment in Ni of the altered surface layer. After extensive sputtering, bombardment-induced segregation of Al at the outermost surface layer of the films was established. Al segregation to the surface was observed during annealing up to 1200 K. The interaction of oxygen with the surface of the alloy films caused surface segregation of Al, accompanied by preferential oxidation of Al.     

Tuning the surface morphology in self-organized ion beam nanopatterning of Si(001) via metal incorporation: from holes to dots

We report on the selective production of self-organized nanohole and nanodot patterns on Si(001) surfaces by ion beam sputtering (IBS) under normal-incidence of 1?keV Ar(+) ions extracted with a cold cathode ion source. For a fixed ion fluence, nanohole patterns are induced for relatively low ion current densities (50-110?μA?cm(-2)), evolving towards nanodot patterns for current densities above 190?μA?cm(-2). Both patterns display similar characteristics in terms of wavelength, short-range hexagonal order and roughness. Rutherford backscattering spectrometry measurements show that the surface morphology is tuned by the incorporation of metals coming from the ion source and sample surroundings during the IBS process. The metal content measured in nanohole patterns is almost twice that found in nanodot morphologies. Thus, the pattern morphology results from the balance between the dependences of the erosion rate on the ion flux, the local surface topography and composition. These nanostructures have promising applications as growth templates for preferential growth on either hillocks or cavities.     

1.5 Effects in Auger electron spectroscopy due to the probing electrons and sputtering

The analysing electron beam and sputtering used for cleaning and depth profiling can alter the chemical composition of composite materials in the near-surface region. Therefore, in a correct analysis several effects caused by the incident ion- or electron beam have to be considered besides the general problem of quantitative AES. No general formalism can be given as these effects depend on the type of material investigated. Examples are given which arise in analysing oxides. carbonates, silicates, homogeneous and heterogeneous alloys.In oxides, the chemical bonding between oxygen and metal is broken up under the influence of the electron beam and oxygen is desorbed. Spectroscopying carbonates, the probing electrons evolve CO₂ which is desorbed and only the remaining oxide can be detected. For silicates, changes in the surface composition due to the electron beam as well as the ion beam were observed. Sputtering of alloys results in preferential sputtering changing the surface composition in accordance to different sputtering yields of the constituents. This is shown for one-phase as well as two-phase alloy systems. For the two-phase system AgCu a further effect is observed which can be explained by pronounced surface diffusion of one constituent, namely silver. Finally for materials of a low concentration of heavy atoms in a matrix of light atoms the knock-in effect is observed.     

Surface morphology and composition of films grown by size-selected Cu nanoclusters

We report the investigation of morphology and composition of copper nanocluster films deposited on Si substrates. The nanoclusters are formed in an aggregation tube at room temperature and magnetron sputtering source is used to get negatively charged Cu-clusters' beam which is subsequently mass-filtered to get size-selected cluster on the substrates as soft-landing process of deposition. For composition of the films, X-ray photoelectron spectroscopy (XPS) technique is used. For morphological changes of the films both scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses are carried out. Additionally, Energy Dispersive X-ray (EDX) spectra support the compositional and structural informations of the film. The analysis of Cu nanoclusters' films reveals that initial nucleation of Cu clusters takes place in the form of isolated islands and the arrival of subsequent Cu clusters onto Si substrates has preferential aggregation around the preceding clusters forming a mound structure.     

Characters of multicomponent lead-free solders

In the process of electronic packaging, such as flip chip technology, under bump metallization (UBM) can be consumed gradually by solder during soldering. Then dissolution of Ni, Au and Cu from UBM into the solder may change the original solder to a multicomponent one especially under the trend of miniaturization. It is quite necessary to evaluate the properties of the multicomponent solders that have new composition after soldering. In this study, the microstructure, thermal and mechanical properties of five types of multicomponent lead-free solders, i.e. Sn–2Cu–0.5Ni, Sn–2Cu–0.5Ni–0.5Au, Sn–3.5Ag–0.5Ni, Sn–3.5Ag–1Cu–0.5Ni and Sn–3.5Ag–2Cu–0.5Ni (all in wt% unless specified otherwise) were investigated. Comparison with eutectic Sn–0.7Cu, Sn–3.5Ag and Sn–3.5Ag–0.7Cu solders was made. There was no obvious difference of the melting point between the multicomponent lead-free solders and the eutectic ones. For Sn–2Cu–0.5Ni solder, Cu₆Sn₅ and (Cu,Ni)₆Sn₅ intermetallic compounds (IMCs) formed. In the case of Sn–2Cu–0.5Ni–0.5Au, besides (Cu,Ni)₆Sn₅, (Cu,Au)₆Sn₅ and (Cu,Ni,Au)₆Sn₅ were also observed. The IMCs formed in Sn–3.5Ag–0.5Ni solder were Ag₃Sn and Ni₃Sn₄. In both Sn–3.5Ag–1Cu–0.5Ni and Sn–3.5Ag–2Cu–0.5Ni solders, Ag₃Sn and (Cu,Ni)₆Sn₅ were detected. The mechanism for the formation of the IMCs was discussed. Tensile test was also conducted. The fractography indicated that all of the multicomponent lead-free solders exhibited a ductile rupture.     

Cell adhesion on modified polyethylene

Polyethylene (PE) was irradiated with 10 and 63 keV Ar⁺ ions to fluences of 1 × 10¹⁷ to 3 × 10¹⁹ m^–2 and then it was grafted with aminoacid (alanine). The changes of surface polarity, electrical conductivity, and oxygen concentration were examined on pristine, as-irradiated, and irradiated-grafted PE. The in vitro adhesion of mice fibroblasts on the modified PE was evaluated 24 hours after inoculation. It was proved that for the PE irradiated at 10 keV ion energy, the presence of chemically bound alanine increases cell adhesion and its homogenity. For PE irradiated with 63 keV ions, however, the alanine grafting leads to a reduction of the number of adhering cells. It was found that a rising surface polarity increases cell adhesion, but when its value is too high the cell adhesion starts to decrease. No correlation between electrical conductivity and cell adhesion was observed. In general, higher cell adhesion is observed on modified PE in comparison with pristine one.     

Depth profiling of fullerene-containing structures by time-of-flight secondary ion mass spectrometry

A new variant of depth profiling for thin-film fullerene-containing organic structures by the method of time-of-flight (TOF) secondary ion mass spectrometry (SIMS) on a TOF.SIMS-5 setup is described. The dependence of the yield of C₆₀ molecular ions on the energy of sputtering ions has been revealed and studied. At an energy of sputtering Cs⁺ ions below 1 keV, the intensity of C₆₀ molecular ions is sufficiently high to make possible both elemental and molecular depth profiling of multicomponent (multilayer) thin-film structures. Promising applications of TOF-SIMS depth profiling for obtaining more detailed information on the real molecular composition of functional organic materials are shown.     

Sputtering of two-phase AgxCux alloys

Elemental sputtering yields from two phase AgCu alloys were measured for 20, 40 and 50 at% Ag. Argon ion bombardment energies were in the range 35–55 keV and the ion dose was 1×10¹⁹ ions cm^–2. The sputtering yield for silver was found to be considerably below what was expected by simple selective sputtering of a two component alloy. Analysis by electron probe X-ray microanalysis and scanning electron microscopy of the eroded surface indicated that surface diffusion of copper from copper rich grains and geometrical constraints in the dense cone forest on Cu/Ag eutectic regions combine to reduce the sputtering yield for silver.     

An orientation competition in yttria-stabilized zirconia thin films fabricated by ion beam assisted sputtering deposition

A previously found orientation competition in ion beam sputtered yttria-stabilized zirconia thin films was studied in detail. The effects of sputtering energy and deposition angle were analyzed in ion sputtered films without assisting ions bombardment. It is found that for normally deposited films, (001) and (011) orientations are favored at low and high sputtering energy respectively. For inclined substrate deposited films, as deposition angle increases, (001), (011) and (111) orientations are advantaged in turn. The results can be attributed to the in-plane energy exchange of deposition atom and adatoms. In ion beam assisting deposited YSZ films of low assisting ions energy and current, a (001) oriented biaxial texture is gradually induced as ion energy increased. In the case of ion beam assisted inclined deposition of 45°, (001) orientation is enhanced and two preferential in-plane orientations are found coexist.     

Studies on sputtering process of multicomponent Zr-Ti-Cu-Ni-Be alloy thin films

Sputter deposition process of a multicomponent Zr-Ti-Cu-Ni-Be metallic alloy has been studied experimentally and by numerical simulations. Monte-Carlo simulations were performed using a model based on thermalization and diffusion of sputtered atoms. Incident energy and angle of sputtered atoms on substrate were obtained from simulations. The incident angular distribution was observed to be a normal distribution at all sputtering pressures. Average incident kinetic energy of the condensing atoms on the substrate was observed to be 0.2-0.3 eV indicating most of them are thermalized. Simulations were extended to predict compositional variations in films prepared at various process conditions. These results were compared with composition of films determined experimentally using Rutherford Backscattering Spectrometry (RBS). Contents of Zr, Ti, Cu and Ni quantified using RBS were in moderate agreement with the simulated composition. Be could not be quantified accurately by RBS largely due to very low energy peak of Be in the spectrum. These studies are shown to be useful in understanding the complexities in multicomponent sputtering.     

Effect of surface treatment on segregation of impurities in haematite

Surface segregation of various impurities such as Mg, Si, Ca, Al and Cr were determined for the haematite phase (Fe₂O₃) annealed in two different gas compositions involving (1) air at 1173 K, and (2) a gas mixture containing sulphur at 773 K. The objective of work was to establish the effect of the gas-phase composition on segregation of lattice defects. The near-surface segregation profiles of the impurities were determined by secondary ion mass spectrometry. The depth profile analysis was made by sputtering using an Ar⁺ primary beam of energy 30 keV. The surface charge was neutralized by an electron gun. It was found that annealing Fe₂O₃ under a gas phase containing sulphur resulted in the formation of an Fe(SO₄)₃ surface layer. It was observed that the two surface treatment procedures applied (both with and without sulphur) result in Mg enrichment in the near-surface region of Fe₂O₃. Si and Ca exhibit an enrichment and impoverishment after the surface treatments 1 and 2, respectively. Finally, the near-surface layer is impoverished in Cr and Al after both types of surface treatment. Experimental results are discussed in terms of segregation driving forces of the respective elements and the possible effect of sulphur on the gas-solid heterogeneous kinetics.     

Surface tension and density measurement of liquid Si–Cu binary alloys

Surface segregation is very important for understanding the surface tension of binary systems. In case of a regular solution, the surface segregation is calculated using the Butler model. However, in the case of a complex system, like those forming intermetallic compounds, it is difficult to express the surface segregation. In order to discuss surface segregation in systems forming intermetallic compounds, we measured the density and surface tension of a Si–Cu binary system. We found the effect of clusters in both density and surface tension experimental data. The composition dependence of surface tension was expressed by a modified ideal solution model.     

Rare-Gas Implantation and Damage of Fullerene at High Fluence

Abstract

100 keV Ar⁺and Kr⁺ ions were implanted into fullerene films up to fluences which exceed the fullerene destruction threshold. The depth profiles of implanted atoms were measured using conventional RBS techniques. The depth profile parameters differ significantly from theoretical estimates and with increasing ion fluence the depth profiles move to the sample surface. This suggests a high degree of fullerene sputtering. In annealing experiments at temperatures up to 375 °C no significant changes of the depth profiles were observed.