Cesium effect on ion-induced secondary photon emission from a GaAs surface

The ion-induced photon emission from excited Ga atoms sputtered from a GaAs single crystal was measured as a function of cesium coverage on the specimen surface. The results showed a remarkable non-linearity in photon yield against cesium coverage. This implies that the photon enhancement effect due to cesium adsorption is nonlocal and relates to the nonradiative deexcitation process of sputtered atoms.     

The spectroscopy of ion-induced photon emission and its application to quantitative surface analysis

Experimentally observed photon spectra produced by ion bombardment of transition elements Sc, Ti, V, Cr, Fe, Ni, and Cu and Zn with Ar⁺ ions are very similar to arc spectra of these same elements, with respect to relative intensities of lines observed. Standard spectrochemical analysis techniques, based on the assumption of local thermodynamic equilibrium in the arc plasma, have been applied to the spectra of the pure elements, to determine the effective arc temperature under relatively clean conditions and in an oxygen environment. These techniques have then been applied to the analysis of a stainless steel sample, again under relatively clean and oxygen environments. In order to explain differences in the $\text{Fe}\text{Cr}$ ratios measured, the behaviour of the intensities of the Fe and Cr emission has been investigated as a function of the oxygen background pressure. The results indicate that while analysis is possible the results depend on the oxygen background pressure.     

A comparison of ion-induced electron emission and secondary ion yields

Ion-induced electron emission from solid surfaces is studied using a beam of caesium ions. Features of the spectra obtained during depth profiling of layered structures suggest a novel technique for investigating ion-induced Auger processes. Depth profiles are presented in terms of measured secondary ion signals, electron-induced Auger emission, and the intensities of features in the ion-induced electron spectra. It is shown that changes in features of the ion-induced electron spectra can be related to changes of chemical composition and sputtering probability. These help in the interpretation of variations in secondary-ion yields with matrix composition during depth profiling.     

A method of quantitative analysis based on ion bombardment induced secondary ion and photon emission

An absolute method of quantitative analysis using both secondary ion and photon emission is described. The method has been applied to the analysis of some NBS steel and Fe/Cr/Ni alloys, with good results. Enhancement of signal strength by means of an O⁺₂ beam or O₂ adsorption is not necessary for this method.     

Angular dependences of sputtering ratio,ion-electron emission coefficient and ion-induced photon emission yield at oblique ion incidence on crystalline targets

The angular dependences of the sputtering ratio, ion-induced photon emission yield and the ion-electron emission coefficient for two faces of a copper'crystal at glancing angles of ion incidence on the targets has been experimentally studied.     

A comment on the effects of Cs on photon and secondary ion emission during sputtering

The effect of Cs on photon and negative ion emission is discussed for situations where the sputtered atom interacts either very weakly or very strongly with the target surface. The experimental data seem to favor the strong interaction case.     

Kinetic ion-induced electron emission from the surface of random solids

This is a review of the published papers devoted to kinetic ion-electron emission from the surface of polycrystalline and amorphous solids. It contains the analysis of energy, angular, temperature, and other dependences of the ion-electron emission coefficient as well as of the energy and angular distributions and the statistics of electron emission events. We also give a brief account of the theoretical studies on the subject.     

Characteristic photon emission from ion bombarded silicon and silica surfaces

Ion bombardment with 50 keV inert gas and reactive gas ions has been used to study the photon emission from excited radiating atoms and ions in the immediate vicinity of the surface of both silicon and silica glass targets (SiO₂).     

Direct comparison of ion scattering and secondary ion emission as tools for analysis of metal surfaces

In this work an experiment is described which allows in situ comparison of SIMS (Secondary Ion Mass Spectrometry) and ISS (Ion Scattering Spectrometry). Measurements on Cu and stainless stell surfaces show that in some respects qualitative agreement between both methods exists. In both cases quantitative surface composition analysis is hampered by the lack of knowledge of secondary ion yields. Especially in case of SIMS the adsorbed species like oxygen have a great influence on the ion yield.     

The use of secondary ion mass spectrometry in surface analysis

Secondary ion mass spectrometry (SIMS) is based on the bombardment of solids by ions and subsequent mass analysis of the sputtered ions or of the post-ionized neutrals. Various models have been proposed for the emission of secondary ions from the target. These models can roughly be grouped into two categories: (a) lonization takes place outside the target; the sputtered particles are assumed to leave the target in an excited or super-excited state; ionization can then result from such processes as Auger de-excitation or resonance ionization. (b) Ions are generated inside the target by collision cascades initiated by a primary impinging ion. Experimental data of the element- and matrix-dependent ion yield and estimates of the minimum detectable concentrations are shown as well as the rate of consumption of the target. Methods for efficient use of the sputtered material will be discussed. Examples of the wide range of applications of SIMS for determination of the chemical composition and structure of the surface layer and for imaging of the distribution of elements in the surface are given. The SIMS results are compared with those of Auger and Ion Scattering Spectrometry. The essentially non-destructive method of static SIMS is shown to be a powerful tool for the investigation of the outermost atomic layers of a solid.     

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.     

Optimum ion implantation and annealing conditions for stimulating secondary negative ion emission

The type, energy, ion dose, and heating temperature required to ensure a stable minimum work function of a surface in one experimental cycle (at least 2–3 min) are determined. Secondary ion mass spectrograms are recorded using Cs⁺, Ba⁺, and Ar⁺ ions. Cu, Al, and Mo samples are studied. The optimum ion implantation conditions and the activation temperature that provide a stable minimum work function of the sample surfaces are found. The samples implanted by Ba⁺ ions withstand higher temperature and current loads than the samples implanted by Cs⁺ ions. However, the work function in the case of Cs⁺ ions decreases stronger (to 1.9 eV). It is shown that neutral sputtered particles do not leave the surface at eφ ≤ 1.85–1.90 eV.     

Enhanced photon emission by field emission resonances and local surface plasmon in tunneling junction

We investigated the photon emission spectra on Ag (111) surface excited by tunneling electrons using a low temperature scanning tunneling microscope in ultrahigh vacuum. Characteristic plasmon modes were illustrated as a function of the bias voltage. The one electron excitation process was revealed by the linear relationship between the luminescence intensity and the tunneling current. Luminescence enhancement is observed in the tunneling regime for the relatively high bias voltages, as well as at the field emission resonance with bias voltage increased up to 9 V. Presence of a silver (Ag) nanoparticle in the tunneling junction results in an abnormally strong photon emission at the high field emission resonances, which is explained by the further enhancement due to coupling between the localized surface plasmon and the vacuum. The results are of potential value for applications where ultimate enhancement of photon emission is desired.     

Absolute photon yield from silicon surface under electron and ion irradiation

The characteristics of the optical radiation accompanying the bombardment of silicon surface by electrons and medium-energy ions have been studied. The continuous radiation observed in this case is related to interband electronic transitions. The characteristic radiation (which is present in both cases), in the case of ion bombardment, is emitted by silicon atoms sputtered in the excited state and scattered helium ions; in the case of electron bombardment, this radiation is emitted by desorbed excited atoms and residual atmosphere molecules, which cover the silicon surface under study.     

Quantitative secondary ion mass spectrometry of fluorocarbon polymers

Secondary ion mass spectrometry (SIMS) is used to measure quantitatively the thickness of thin (6–160 Å) polyperfluoroether films on silicon and gold surfaces. Linear relationship between ellipsometrically measured thicknesses and integrated SIMS signals is demonstrated. Time dependence of SIMS signals indicates that the polymeric films have a uniform thickness down to the thinnest layers studied. In the lower limit, the fluorocarbon polymers have extended, flat conformation due to polymer-substrate interactions. Sputtering yield and effective sputtering depth of oxygen ions are determined for these liquid polymers. It is also shown that organic adsorbates reside between the solid surface and the low surface tension fluorocarbon films.     

Surface analytical applications of ion-induced secondary emission target currents: I. Oxidation of In and Cu

Measurements of ion-induced secondary emission target currents afford a sensitive and rapid means of following the adsorption process. The method has been applied in this instance to monitor O₂ uptake by polycrystalline In and Cu substrates.     

Structure effects in secondary ion emission of metals and alloys

This review is devoted to structure effects related to the influence of the electronic system of the target and its phase composition in the secondary ion emission (SIE) of metals and alloys. Data on the anisotropy of SIE of single crystals and orientation effects playing a special role both in the understanding the physical processes upon emission of ions and in the practical use of the secondary-ion mass-spectroscopy technique are considered.     

Ion-induced photon emission: Neutralization mechanism of surface plasmon excitation

A mechanism of surface plasmon excitation occurring in any, including resonant, processes of neutralization of positive and negative ions near metal surface is proposed and a model of this mechanism is developed. High efficiency of the mechanism and adequacy of the model to the ion-induced photon emission data are demonstrated. The main formulas of the model are discussed in terms of the quantum-mechanical perturbation theory and dielectric formalism.     

基于二次电子发射的离子束剖面测量

介绍了利用二次电子发射测量束流强度分布的基本原理。针对能量为几十keV的低能离子束,制作了一个基于印刷线路板工艺的离子束剖面测量系统模型。模型采用宽度1.8 mm的金属条作为收集电极,相邻两条之间的间距为2 mm。利用电子回旋共振源对束流剖面测量系统进行了性能测试,考察了网栅电压对信号收集的影响以及系统的线性响应和成像特性。结果表明,探测器输出信号与束流强度之间具有较好的线性关系,系统能得到离子束的一维横向强度分布,位置分辨率2 mm。     

基于二次电子发射的离子束剖面测量

介绍了利用二次电子发射测量束流强度分布的基本原理。针对能量为几十keV的低能离子束,制作了一个基于印刷线路板工艺的离子束剖面测量系统模型。模型采用宽度1.8 mm的金属条作为收集电极,相邻两条之间的间距为2 mm。利用电子回旋共振源对束流剖面测量系统进行了性能测试,考察了网栅电压对信号收集的影响以及系统的线性响应和成像特性。结果表明,探测器输出信号与束流强度之间具有较好的线性关系,系统能得到离子束的一维横向强度分布,位置分辨率2 mm。