Materials processing by gas cluster ion beams

This paper discusses the principles and experimental status of gas cluster ion beam (GCIB) processing as a promising surface modification technique for practical industrial applications. Theoretical and experimental characteristics of GCIB processes and of related equipment development are described from the moment of neutral cluster formation, through ionization, acceleration and impact upon a surface. The impact of an accelerated cluster ion upon a target surface imparts very high energy densities into the impact area and produces non-linear effects that are not observed in the impacts of atomic ions. Unique characteristics of GCIB bombardment have been found to offer potential for various industrial applications that cannot be achieved by conventional ion beam processing. Among prospective applications are included shallow ion implantation, high rate sputtering, surface cleaning and smoothing, and low temperature thin film formation. Sputtering effects produced by cluster ion impact are particularly interesting. High sputtering yields and lateral distribution of sputtered atoms cause surface smoothing effects which cannot be achieved with monomer ion beams. Surface smoothing to atomic levels is expected to become the first production use of GCIB.     

Mixed oxide coatings for optics

Material mixtures offer new possibilities for synthesizing coating materials with tailored optical and mechanical properties. We present experimental results on mixtures of HfO2, ZrO2, and Al2O3, pursuing applications in UV coating technology, while the mixtures are prepared by magnetron sputtering, ion beam sputtering, plasma ion-assisted deposition (PIAD), and electron beam evaporation without assistance. The properties investigated include the refractive index, optical gap, thermal shift, and mechanical stress. The first high reflectors for UV applications have been deposited by PIAD.     

Depth profiling of organic films with X-ray photoelectron spectroscopy using C60+ and Ar+ co-sputtering

By sputtering organic films with 10 kV, 10 nA C60+ and 0.2 kV, 300 nA Ar+ ion beams concurrently and analyzing the newly exposed surface with X-ray photoelectron spectroscopy, organic thin-film devices including an organic light-emitting diode and a polymer solar cell with an inverted structure are profiled. The chemical composition and the structure of each layer are preserved and clearly observable. Although C60+ sputtering is proven to be useful for analyzing organic thin-films, thick organic-devices cannot be profiled without the low-energy Ar+ beam co-sputtering due to the nonconstant sputtering rate of the C60+ beam. Various combinations of ion-beam doses are studied in this research. It is found that a high dosage of the Ar+ beam interferes with the C60+ ion beam, and the sputtering rate decreases with increasing the total ion current. The results suggest that the low-energy single-atom projectile can disrupt the atom deposition from the cluster ion beams and greatly extend the application of the cluster ion-sputtering. By achievement of a steady sputtering rate while minimizing the damage accumulation, this research paves the way to profiling soft matter and organic electronics.     

SURFACE ROUGHNESS OF SPUTTERED SILICON. I. SURFACE MODELING

A mathematical model for the calculation of surface roughness was developed for focused ion beam (FIB) sputtering. The surface roughness function is a combination of the beam function and the material function. The beam function includes ion type, ion acceleration energy, and beam parameters. Furthermore, the beam parameter incorporates ion flux, the ion beam intensity distribution profile, tailing and neighboring of the successive beams, dwell time, etc. The intensity distribution inside the ion beam is considered to be Gaussian. The cumulative intensity over the total milling area is calculated by the algebraic summation of individual beam intensity delivered to every pixel successively. The material function includes the inherent material properties related to the ion beam micromachining. If one knows the beam function and material function, surface roughness at the bottom of the sputtered features can be calculated using this model.     

1.13 Plating with ion accelerators

Formation of thin films by sputtering and ion plating are well-known techniques. The present contribution describes ion beam plating which is a novel technique somewhat related to ion plating. Thin films of metal compounds on a substrate are decomposed by ionic bombardment resulting in films with good adherence to substrate. The formation of thin palladium films on silicon surfaces will be discussed in detail. Halide compounds of palladium dissolved in organic solvents are sprayed onto the substrate. Subsequently these thin films are exposed to ion beams of inert gases in the energy range below 100 keV. After ion exposure, remains of the halide compound are removed chemically. The ion beam plated film, which appears mirror-like, is then investigated by scanning electron microscopy, proton back-scattering in order to characterise the ion beam plated film. The possible applications of ion beam plated films will be discussed.     

1.6 Composition and stress state of thin films deposited by ion beam sputtering

The ion beam sputtering technique offers several advantages over conventional sputtering systems. This technique operates at a lower pressure and substrate temperature than conventional sputtering. In addition, the angle of deposition which is easily varied with ion beam sputtering is essentially fixed in dc and rf diode sputtering. As a result of these advantages, many of the parameters which effect film stress, resistivity, and grain size can be varied independently.Several properties of ion beam sputtered Ni, Al, Ni₃Al and Au thin films have been evaluated as a function of ion beam current density, target material, and the angle and distance of the substrate from the target.The grain size and stress were found to vary with the angle of deposition. There is an apparent correlation between electrical resistivity and the oxygen content in the films. Both properties depend upon the grain size. The stress levels of the films are shown to be influenced by the oxygen content. These experimental results are discussed in light of models proposed to explain the origin of stress in thin films.     

Ion beam modification of materials for industry

The use of ion beams as an effective means for changing the surface properties of materials has gained increasing interest in the last few years. The ion beam processes, depending on their energy, can be divided into two different categories. (1) Energetic ion beams used in the ion implantation process (10–500 keV) are capable of penetrating hundreds of atomic layers into a material and have been shown to change the mechanical and chemical surface properties of the material. (2) Lower energy ions used in ion beam sputtering, ion plating and plasma ion deposition are less penetrating and are used to build thin layer coatings on the surface of materials with unusually attractive mechanical and adhesive qualities.This paper concentrates on the industrial application of the ion implantation process. Based on the field results available and the unique capabilities of the ion implantation process (dimensional stability, lack of delamination problems associated with hard coatings etc.) several prime candidates for immediate large-scale ion implantation processing are identified. The common criteria in these applications (e.g. high value-added components, new technologies) are discussed.Applications for ion sputtering, ion beam mixing and plasma ion synthesis of i-BN are presented.     

Studies of diamond-like carbon films prepared by ion beam-assisted deposition

Ion beam-assisted deposition offers a novel and unique process to prepare diamond-like carbon (DLC) films at room temperature, with particularly good interface adhesion. This advantage was explored in this study to deposit highly wear-resistant coating on bearing 52100 steel. Both dual ion beam sputtering and ion beam deposition were employed. Various bombarding species and energy were investigated to optimize the process. Raman, X-ray photoelectron and Auger electron spectroscopy were used to characterize the bonding structure of DLC. Extensive experiments were carried out to examine the tribological behaviour of the DLC/52100 system. A metal intermediate layer can help tremendously in wear resistance. The results are optimistic and may lead to useful applications.     

磁控溅射法制备高反射铝膜

通过先后调整溅射沉积时间、溅射功率以及溅射气压等镀膜参数,然后结合所镀样品的反射率测量,分析了镀膜参数对铝膜反射率的影响;通过调整不同的离子束清洗时间,结合所镀样品的太阳光谱反射率测量以及附着力测试,研究了离子束清洗对铝膜性能的影响。结果表明,在这些影响因素中离子束清洗对铝膜性能的影响很大。     

Evolution of texture of CeO2 thin film buffer layers prepared by ion-assisted deposition

Evolution of texture in CeO₂ thin films was studied using biased magnetron sputtering and ion beam assisted magnetron sputtering. Films deposited onto polycrystalline Hastelloy metal substrates by biased magnetron sputtering develop preferential (002) growth as the energy of the ions is increased from zero to above 100 eV. For ion beam assisted magnetron sputtering (magnetron IBAD), with the ion beam directed at 55° to the substrate normal, the evolution of biaxial alignment is controlled by the ion beam energy and the ion/atom arrival rate ratio. Ion beam energies >200 eV and ion/atom ratios >0.3 lead to perfect biaxial alignment with one pole aligned along the ion beam direction. Epitaxial growth of CeO₂ films was observed for MgO(001) substrates at 750°C without any ion assistance, and on yttria-stabilised zirconia (001) buffer layers at room temperature and a bias of −80 V.     

Schichten über Schichten

Films over films: innovative coatings for complex applications Thin films and coatings have developed as a prerequisite for many technical applications. In this paper, some applications for electrical, electronic, biomedical and optical applications are presented. In this contribution, examples for coatings for conductive and transparent films in photovoltaics, films for biomedical electrodes, for semiconductor contacts and for high‐temperature contacts are presented and discussed. The films are prepared by magnetron‐sputtering and pulsed laser deposition. The influence of the processing parameters on the functional properties of the films is presented.     

Processes of the activated reactive evaporation type and their tribological applications

Plasma-assisted deposition processes have created a breakthrough in the deposition of compounds particularly the refractory compounds such as oxides, carbides, nitrides etc. Processes such as sputtering or ion plating inherently contain a plasma in the space between the target and the substrate. Evaporation and chemical vapor deposition processes have to be modified to include a plasma. In all of these reactive deposition processes the plasma plays a vital role in providing the activation energy necessary to carry out the process or to enhance its efficiency. All types of vapor sources can be used in these processes. The original development in 1971 used a thermionic electron beam evaporation source. Subsequently, resistance- heated, arc, induction, plasma electron beam and sputtering sources have all been used. In this paper we shall discuss the processes and the influence of deposition parameters on the microstructure and properties of compounds. Specific examples of the use of these compounds in tribological applications are considered.     

Development of ion beam sputtering techniques for actinide target preparation

Ion beam sputtering is a routine method for the preparation of thin films used as targets because it allows the use of a minimum quantity of starting material, and losses are much lower than most other vacuum deposition techniques. Work is underway in the Isotope Research Materials Laboratory (IRML) at ORNL to develop the techniques that will make the preparation of actinide targets up to 100 μg/cm² by ion beam sputtering a routinely available service from IRML. The preparation of the actinide material in a form suitable for sputtering is a key to this technique, as is designing a sputtering system that allows the flexibility required for custom-ordered target production. At present, development work is being conducted on low-activity actinides in a bench-top system. The system will then be installed in a hood or glove box approved for radioactive materials handling where processing of radium, actinium, and plutonium isotopes among others will be performed.     

Hg1-xCdxTe材料AES定量分析中的电子束和离子束效应

在Hg1-xCdxTe材料的AES分析中 ,由于分析电子束辐照作用 ,可诱导表面Hg原子的脱附和热升华 ,导致短时间内样品表面严重失Hg ,使AES定量分析结果产生很大的误差。实验结果表明 ,在超高真空中分析电子束辐照下局部Hg元素的挥发损失以负指数关系进行。通过选择离子束溅射速率大于电子束蒸发速率 ,并在溅射的同时进行俄歇信号收集 ,则可减小或消除分析电子束对元素Hg的蒸发作用 ,获得稳定的俄歇信号。实验结果还指出 ,溅射离子束的参数会影响元素的相对溅射产额 ,具体定量分析时应选择相同的溅射条件     

Laser-assisted maskless microdeposition of silver nano-particles on a magnesium substrate

Laser-assisted maskless microdeposition and silver nano-particles are used to create micro-scale patterns with nano-scale topography on a magnesium substrate for potential biomedical applications. By controlling the processing parameters, various patterns and properties are achieved. The electron microscopy analysis of a sample prepared by focused ion beam microscope provides evidence for excellent bounding and effective surface alloying across the interface.     

气离溅射离子镀制氮化钛

本文详细介绍了气体离子源增强磁控溅射(气离溅射)反应离子镀膜技术和系统配置.特别是首次提出空分气离溅射的新概念,实现了磁控溅射金属镀膜过程和气体离子轰击化学反应过程在真空室内空间上的分离,从而保证空分气离溅射反应离子镀膜过程的长时间稳定性、重复性和一致性.当磁控溅射源采用中频电源驱动、最新开发的气体离子源采用脉冲直流电源后,实现了最佳的设备组合,可镀制出高品质的TiN膜层.     

Ionen- und plasmagestützte Verfahren der Oberflächentechnik für die Randschichtbehandlung von Leichtmetallwerkstoffen

Surface engineering of light weight materials with ion- and plasma-assisted methods Increasing applications of light weight materials are expected in the future. Pursuing this trend surface engineering of these materials – especially ion- and plasma-assisted methods – swill be of increasing interest to enhance their wear and corrosion resistance. In a research co-operation some promising methods were examined on different aluminium and titanium alloys to assess their potential to increase the surface properties. Among these were magnetron sputtering of chromium nitride, ion beam assisted deposition of Cr/CrN and Al/A₂O₃ layers, ion implantation and ion beam assisted nitriding. Compared to the steel substrates the assessment of the mechanical properties such as the critical load of the scratch test of the coated light weight materials is different. Furthermore, it could be shown that both spherical section and glow discharge optical spectroscopy are useful methods to characterize the near-surface zone influenced by ion implantation.     

Influence of ion bombardment on depth resolution in Auger electron spectroscopy analysis of thin gold films on nickel

Thin film Auger electron analysis of gold films on nickel was performed while simultaneously sputtering with argon ions. The influence of film thickness, electron and ion beam energies, ion beam current density and initial surface roughness on depth resolution was investigated. The intrinsic limitations of depth resolution result from the escape depth of Auger electrons and from atomic mixing due to ion impact. Prolonged ion sputtering leads to the development of microroughness. The influence of this last effect is described by an empirical correlation which shows the width of the transition region to increase with the square root of the product of ion beam energy and film thickness. The original surface roughness also affects depth resolution but, at higher ion beam energies (2 keV) in particular, its influence is somewhat masked by ion-induced microroughness. Optimum resolution (5% of film thickness) in depth profiling is obtained by employing well-polished samples and low ion beam energies.     

气体离化团束溅射研究

研究了CO2，Ar离化团束对不同金属系统及SiO2表面的溅射效应。离化团束的溅射产额比之单体离子束高100倍以上。气体离化团束的高溅射产额可能是由于多体碰撞、侧向溅射及高能量密度的照射引起的。     

Matrix-enhanced secondary ion mass spectrometry: a method for molecular analysis of solid surfaces

A new methodology, matrix-enhanced secondary ion mass spectrometry (ME-SIMS), is reported for the molecular analysis of biomaterials. The technique applies static secondary ion mass spectrometry (SSIMS) techniques to samples prepared in a solid organic matrix similar to sample preparations used in matrix-assisted laser desorption/ionization (MALDI). Molecular ions are observed in this ion beam sputtering of organic mixtures for peptides and oligonucleotides up to masses on the order of 10?000 Da. This matrix-enhanced SIMS exhibits substantial increases in the ionization efficiency of selected analyte molecules compared to conventional SSIMS processes. Thus, higher mass peptides, proteins, and nucleic acids become accessible to near-surface analysis by ion beam techniques, and subpicomole sensitivity has been demonstrated. A number of matrices were examined for their efficiency in ME-SIMS applications, and these initial matrix studies focused on common MALDI matrices and their isomers. The results of this survey indicate that 2,5-dihydroxybenzoic acid provides the best general enhancement of molecular secondary ions emitted from analyte/matrix mixtures.