高能氮离子轰击对四面体非晶碳膜的表面改性和摩擦系数影响的研究

利用过滤阴极真空电弧技术制备了sp³键含量不小于80%的四面体非晶碳(ta-C)膜.利用冷阴极潘宁离子源产生不同能量的氮离子对制备的ta-C薄膜进行轰击,通过X射线光电子能谱和原子力显微镜对薄膜表面结构与形貌进行分析研究.研究表明,随着氮离子的轰击能量的增大,薄膜中的CN键结构略有增大,形成了轻N掺杂;同时,在薄膜表层发生了sp³键结构向sp²键结构的转化;薄膜的表面粗糙度在经过氮离子轰击后从0.2 nm减小至0.18 nm,然后随着轰击能 关键词： 四面体非晶碳 X射线光电子能谱 摩擦系数     

Preferential sputtering of TIC under keV Ar+ ion bombardment: Simultaneous sputtering-ISS measurement with He+ and Ar+ ions

The composition change of the outermost atom layer of TiC(110) under ion bombardment with 1.5–3 keV He⁺ and He⁺ + Ar⁺ ions has been measured by ion scattering spectroscopy with He⁺ ions at different sample temperatures. It has been found that the preferential sputtering of C atoms takes place for both the He⁺ and Ar⁺ ion bombardment, however the preferred sputtering is more pronounced for Ar⁺ ions than for He⁺ ions. The ion bombardment with He⁺ ions at elevated sample temperatures hardly results in any change in surface composition below ～800°C, while Ar⁺ ion bombardment results in C enrichment for elevated temperatures as reported so far.     

ISS measurement of surface composition of AuCu alloys by simultaneous ion bombardments with Ar+ and He + ions

Surface composition of Au-Cu(43 at%) alloy under 1.5–5 keV argon ion bombardment has been investigated by ion scattering spectroscopy (ISS). In this experiment, we adopted a specific technique to use mixed He⁺ and Ar⁺ ions as primary beam in order to perform sputtering (Ar⁺) and ISS measurement (He⁺) simultaneously. The outermost atom layer of Au-Cu alloys under Ar⁺ ion bombardment is Au-rich leading to the conclusion that Ar⁺ ion bombardment of AuCu alloys causes the preferential sputtering of Cu atoms, resulting in a Au-rich outermost atom layer and a depletion layer of Au atoms beneath the outermost atom layer due to ion-beam-enhanced surface segregation. This result explains the experimental results obtained by AES as well.     

Temperature dependence of compositional changes of SiO2 surface during ion and electron bombardment

The influence of ion (Ar⁺ 0.5 keV, 2 microA/cm²) and electron (2 keV, 2 mA/cm²) bombardment on the elemental composition of SiO₂ was investigated in the temperature range of 270–790 K. Elemental composition was controlled by AES. It was found that both ion and electron bombardment resulted in an increasing amount of Si₉₂ (elemental silicon) and in decreasing amounts of both O₅₁₀ and Si₇₈ (silicon bound to oxygen). The temperature influence on the composition of SiO₂ is negligible under ion bombardment while the amount of Si₉₂ strongly increases under electron bombardment at temperatures exceeding 600 K. The mechanism of temperature dependence is discussed.     

AES analysis of nitridation of Si(100) by 2–10 keV N+2 ion beams

Ion beam nitridation of Si(100) as a function of N⁺₂ ion energy in the range of 2–10 keV has been investigated by in-situ Auger electron spectroscopy (AES) analysis and Ar⁺ depth profiling. The AES measurements show that the nitride films formed by 4–10 keV N⁺₂ ion bombardment are relatively uniform and have a composition of near stoichiometric silicon nitride (Si₃N₄), but that formed by 2 keV N⁺₂ ion bombardment is N-rich on the film surface. Formation of the surface N-rich film by 2 keV N⁺₂ ion bombardment can be attributed to radiation-enhanced diffusion of interstitial N atoms and a lower self-sputtering yield. AES depth profile measurements indicate that the thicknesses of nitride films appear to increase with ion energy in the range from 2 to 10 keV and the rate of increase of film thickness is most rapid in the 4–10 keV range. The nitridation reaction process which differs from that of low-energy (< 1 keV) N⁺₂ ion bombardment is explained in terms of ion implantation, physical sputtering, chemical reaction and radiation-enhanced diffusion of interstitial N atoms.     

A SIMS study of ion beam induced migration of nitrogen in thermally oxidized silicon

The potential use of thin silicon nitroxide films as gate dielectrics in VLSI MOS devices has motivated much recent work. The present study shows that positive ion bombardment, as encountered in sputter depth profiling or ion implantation, can induce considerable movement of nitrogen in thin thermal oxide films on silicon. Low energy N⁺₂ implants are performed in-situ in a SIMS apparatus and are subsequently depth profiled. The effect of implant dose and oxide thickness are examined and comparisons are made to films prepared by rapid thermal nitridation and LPCVD. Profiles obtained under O⁺₂, O^-, and Cs⁺ bombardment are also compared. SIMS depth profiles of implanted 200 Å oxides using positive ion bombardment show a depletion of nitrogen near the surface, a shoulder in the nitrogen concentration near the Si-SiO₂ interface, and a peak in this concentration at the interface. Negative ion bombardment did not induce a shoulder-peak structure at the interface. The implications of these results are discussed.     

Multiple inner-shell ionization in oxygen produced by ion bombardment in the MeV range

Oxygen X-ray spectra from oxide targets by proton, helium, nitrogen and argon ion bombardment are studied. K satellite and hypersatellite peaks are observed. In light ion bombardment, X-ray production of the double K-shell ionization indicated large deviation from the Z²₁ dependence.     

High-intensity Si cluster ion emission from a silicon target bombarded with large Ar cluster ions

Secondary ions emitted from Si targets were measured with a quadrupole mass spectrometer under large Ar cluster and monomer ion bombardment. Incident ion beams with energies from 7.5 to 25 keV were used and the mean size of the Ar cluster ion was about 1000 atoms/cluster. Si_n⁺ ions with n values up to n = 8 were detected under Ar cluster ion bombardment, whereas Si cluster ions were scarcely detected under Ar monomer ion bombardment. These cluster ion yields showed the power law dependence on the cluster size.     

Randomisation of crystal structure within energetic collision cascades revealed by the sputtering of Au single crystals during ion bombardment

The ratio of random to preferential atomic ejection which occurs from the surface of a gold single crystal during ion bombardment has been found to be very sensitive to the ion mass. For instance, in the case of 50 keV Ne⁺ ion bombardment preferential ejection dominates, whereas in the case of 50 keV Au⁺ ion bombardment preferential ejection is only a small fraction of the total. These results are interpreted in terms of a dynamic randomisation of the crystal lattice which occurs during the creation of energetic atomic collision cascades. The disorder occurs so rapidly that a substantial fraction of atoms sputtered from the surface are ejected from an essentially random structure. It is thought that such gross disorder is only a transient phenomenon, and leaves no significant permanent effects, except perhaps for a few clustered defects.     

Chemical effects on beryllium K X-ray spectra produced by heavy ion bombardment

Beryllium X-ray spectra from Be and BeO targets by proton, helium, nitrogen and argon ion bombardment have been measured. In the oxide, chemical shifts of K_α and K²_α X-ray lines are similar magnitude and the intense satellite KL and hypersatellite K²L lines are observed by heavy ion bombardment.     

A CEMS investigation of57Fe+Al implanted in Al foil

⁵⁷Fe implanted and post Al implanted in aluminum foil have been performed at low energy of 27keV and the CEMS shows the formation of intermetallic compounds FeAlσ and Fe₂Alσ during the ion bombardment. The results are discussed with the enhanced diffusion by energetic ion bombardment.     

Sputter damage in Si surface by low energy Ar+ ion bombardment

The damage distributions in Si(1 0 0) surface after 1.0 and 0.5 keV Ar⁺ ion bombardment were studied using MEIS and Molecular dynamic (MD) simulation. The primary Ar⁺ ion beam direction was varied from surface normal to glancing angle. The MEIS results show that the damage thickness in 1.0 keV Ar ion bombardment is reduced from about 7.7 nm at surface normal incidence to 1.3 nm at the incident angle of 80°. However, the damage thickness in 0.5 keV Ar ion bombardment is reduced from 5.1 nm at surface normal incidence to 0.5 nm at the incident angle of 80°. The maximum atomic concentration of implanted Ar atoms after 1 keV ion bombardment is about 10.5 at% at the depth of 2.5 nm at surface normal incidence and about 2.0 at% at the depth of 1.2 nm at the incident angle of 80°. However, after 0.5 keV ion bombardments, it is 8.0 at% at the depth of 2.0 nm for surface normal incidence and the in-depth Ar distribution cannot be observable at the incident angle of 80°. MD simulation reproduced the damage distribution quantitatively.     

Evaluation of secondary ion yield enhancement from polymer material by using TOF-SIMS equipped with a gold cluster ion source

We investigated the enhancement of the secondary ion intensity in the TOF-SIMS spectra obtained by Au⁺ and Au₃⁺ bombardment in comparison with Ga⁺ excitation using polymer samples with different molecular weight distributions. Since the polymer samples used in this experiment have a wide molecular weight distribution, the advantages of the gold cluster primary ion source over monoatomic ion could accurately be evaluated. It was observed that the degree of fragmentation decreased by the usage of cluster primary ion beam compared with monoatomic ion beam, which was observed as a shift of the intensity distribution in the spectra. It was also found out that the mass effect of Au⁺ and Ga⁺ as monoatomic primary ion, resulted in about 10-60 times of enhancement for both samples with different molecular distributions. On the other hand, the Au₃⁺ bombardment caused intensity enhancement about 100-2600 compared with Ga⁺ bombardment, depending on the mass range of the detected secondary ion species. The cluster primary ion effect of Au₃⁺, compared with Au⁺, therefore, was estimated to be about 10-45.     

氩离子轰击对四面体非晶碳膜内应力和摩擦系数影响的研究

利用磁过滤真空阴极电弧技术制备了sp³键大于80%的四面体非晶碳(ta-C)薄膜, 通过冷阴极离子源产生keV能量的氩离子轰击ta-C薄膜,研究了氩离子轰击能量对ta-C薄膜结构, 内应力以及耐磨性的影响.通过X射线光电子能谱和原子力显微镜研究了氩离子轰击对薄膜结构 与表面形貌的改性,研究表明,氩离子轰击诱导了ta-C薄膜中sp³键向sp²键的转化, 并且随着氩离子轰击能量的增大,薄膜中sp²键的含量逐渐增多, 薄膜内应力随着氩离子轰击能量的增大逐渐减小.氩离子轰击对薄膜的表面形貌有较大影响, 在薄膜表面形成刻蚀坑,并且改变了薄膜的表面粗糙度,随着氩离子轰击能量的增大, 薄膜的表面粗糙度也会逐渐增大.通过摩擦磨损仪的测试结果,氩离子轰击对薄膜的初始摩擦系数影响较大, 但是对薄膜的稳定摩擦系数影响较小,经过氩离子轰击前后的ta-C薄膜的摩擦系数为0.1左右, 并且具有优异的耐磨性.     

On the nature of ion bombardment-induced phase transformations in films of transition metals

Abstract

Electron diffraction studies have been made of polycrystalline Ni films irradiated with well separated beams of ions of different nature, namely ions of inert (He⁺, Ne⁺, Ar⁺, Kr⁺, Xe⁺) and reactive (N⁺ and O⁺) gases. The Ni films were prepared under vacuum conditions (P? 3·10^?6Pa during evaporation) preventing an appreciable contamination of the films with impurities. The samples were irradiated at T? 300 K with ion beams of energies from 10 to 100 keV in the dose range between 5·10¹⁶ cm^?2 and the value leading to sample destruction.

Irradiation with noble gas ions revealed no phase transitions in the Ni films. A similar result was obtained in irradiation of Fe and Cr films with He⁺ ions. The bombardment of Ni films with reactive gas ions does cause changes in the lattice structure of the samples under study, depending on the nature of the bombarding ions. The N⁺ ion bombardment gives rise to the hcp phase with the lattice parameters typical of the Ni₃N compound, and the O⁺ ion bombardment results in the fcc phase with the NiO-type parameter.

The conclusion is drawn on the chemical origin of the phase transformations in the Ni films under ion bombardment. The necessity of revising the concept about the polymorphous nature of phase transformations induced in the films of transition metals by ion bombardment is substantiated.     

Characterization and ion-induced degradation of cross-linked poly(methyl methacrylate) studied using time of flight secondary ion mass spectrometry

In this study, a series of random copolymers of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) were prepared as surface-initiated polymer (SIP) films on silicon substrates using atom transfer radical polymerization. Positive and negative ion static time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to characterize SIP films with different MMA/EGDMA monomer ratios in an attempt to quantify their surface composition. However, matrix effects in the positive and negative ion modes led to preferential secondary ion generation from the EGDMA monomer and suppression of secondary ions characteristic of the MMA monomer, precluding accurate quantification using standard linear quantification methods. Ion-induced degradation of these films under 5 keV SF₅⁺ bombardment was also examined to determine the effect of cross-linking on the accumulation of ion-induced damage. Increasing incorporation of the EGDMA cross-linker in the SIP films decreased the sputter rate and increased the rate of damage accumulation under extended (>10¹⁴ ions/cm²) 5 keV SF₅⁺ bombardment. Comparison of the ion bombardment data with thermal degradation of cross-linked PMMA suggests that the presence of the cross-linker impedes degradation by depolymerization, resulting in ion-induced damage accumulation. The increased rate of ion-induced damage accumulation with increased cross-link density also suggests that polymers that can form cross-links during ion bombardment are less amenable to depth profiling using polyatomic primary ions.     

Polyethylene terephthalate (PET) bulk film analysis using C60, Au3, and Au primary ion beams

The damage characteristics of polyethylene terephthalate (PET) have been studied under bombardment by C₆₀⁺, Au₃⁺ and Au⁺ primary ions. The observed damage cross-sections for the three ion beams are not dramatically different. The secondary ion yields however were significantly enhanced by the polyatomic primary ions where the secondary ion yield of the [M + H]⁺ is on average 5× higher for C₆₀⁺ than Au₃⁺ and 8× higher for Au₃⁺ than Au⁺. Damage accumulates under Au⁺ and Au₃⁺ bombardment while C₆₀⁺ bombardment shows a lack of damage accumulation throughout the depth profile of the PET thick film up to an ion dose of ∼1 × 10¹⁵ ions cm⁻². These properties of C₆₀⁺ bombardment suggest that the primary ion will be a useful molecular depth profiling tool.     

Molecular ion yield enhancement induced by gold deposition in static secondary ion mass spectrometry

Static ToF-SIMS was used to evaluate the effect of gold condensation as a sample treatment prior to analysis. The experiments were carried out with a model molecular layer (Triacontane M = 422.4 Da), upon atomic (In⁺) and polyatomic (Bi₃⁺) projectile bombardment. The results indicate that the effect of molecular ion yield improvement using gold metallization exists only under atomic projectile impact. While the quasi-molecular ion (M+Au)⁺ signal can become two orders of magnitude larger than that of the deprotonated molecular ion from the pristine sample under In⁺ bombardment, it barely reaches the initial intensity of (M−H)⁺ when Bi₃⁺ projectiles are used. The differences observed for mono- and polyatomic primary ion bombardment might be explained by differences in near-surface energy deposition, which influences the sputtering and ionization processes.     

Composition,morphology, and electronic structure of the nanophases created on the SiO<Subscript>2</Subscript> Surface by Ar<Superscript>+</Superscript> ion bombardment

The influence of Ar⁺ bombardment on the composition and the structure of the SiO₂/Si surface is studied. A thin Si film is found to form on the SiO₂ surface subjected to high-dose ion bombardment.     

The effect of C60 cluster ion beam bombardment in sputter depth profiling of organic-inorganic hybrid multiple thin films

The effects of C₆₀ cluster ion beam bombardment in sputter depth profiling of inorganic-organic hybrid multiple nm thin films were studied. The dependence of SIMS depth profiles on sputter ion species such as 500 eV Cs⁺, 10 keV C₆₀⁺, 20 keV C₆₀²⁺ and 30 keV C₆₀³⁺ was investigated to study the effect of cluster ion bombardment on depth resolution, sputtering yield, damage accumulation, and sampling depth.