Energetic ion

Atom-surface interactions are intrinsically many-body problems which are known to have no analytical solutions. Due to the shorter de Broglie wavelengdi of an energetic ion than solid interatomic spacings, the energetic atom-surface interaction problem can be treated by classical mechanics. In the classical mechanical... 

Chaimelling phenomena were studied before Rutherford backscattering was developed as a routine analytical tool. Chaimelling phenomena are also important in ion implantation, where the incident ions can be steered along the lattice planes and rows. Channelling leads to a deep penetration of the incident ions to deptlis below that found in the nonnal, near Gaussian, depth distributions characterized by non-chaimelled energetic ions. Even today, implanted chaimelled... 

Figure Bl.24.14. A schematic diagram of x-ray generation by energetic particle excitation, (a) A beam of energetic ions is used to eject inner-shell electrons from atoms in a sample, (b) These vacancies are filled by outer-shell electrons and the electrons make a transition in energy in moving from one level to another this energy is released in the fomi of characteristic x-rays, the energy of which identifies that particular atom. The x-rays that are emitted from the sample are measured witli an energy dispersive detector.

A microbe employs a focused beams of energetic ions, to provide infomiation on the spatial distribution of elements at concentration levels that range from major elements to a few parts per million [27]. The range of teclmiques available that allowed depth infomiation plus elemental composition to be obtained could all be used in exactly the same way it simply became possible to obtain lateral infomiation simultaneously. 

The basis of the nuclear microprobe (NMP) is a source of energetic ions from a particle accelerator. These... 

The reaction mechanisms of plasma polymerization processes are not understood in detail. Poll et al [34] (figure C2.13.6) proposed a possible generic reaction sequence. Plasma-initiated polymerization can lead to the polymerization of a suitable monomer directly at the surface. The reaction is probably triggered by collisions of energetic ions or electrons, energetic photons or interactions of metastables or free radicals produced in the plasma with the surface. Activation processes in the plasma and the film fonnation at the surface may also result in the fonnation of non-reactive products. 

Abrams C F and Graves D B 1998 Energetic Ion bombardment of SIOj surfaces molecular dynamics simulations J. Vac. Sc/. Technol. A 16 3006-19... 

Plasmas at fusion temperatures cannot be kept in ordinary containers because the energetic ions and electrons would rapidly coUide with the walls and dissipate theit energy. A significant loss mechanism results from enhanced radiation by the electrons in the presence of impurity ions sputtered off the container walls by the plasma. Therefore, some method must be found to contain the plasma at elevated temperature without using material containers. 

Metallization layers are generally deposited either by CVD or by physical vapor deposition methods such as evaporation (qv) or sputtering. In recent years sputter deposition has become the predominant technique for aluminum metallization. Energetic ions are used to bombard a target such as soHd aluminum to release atoms that subsequentiy condense on the desired substrate surface. The quaUty of the deposited layers depends on the cleanliness and efficiency of the vacuum systems used in the process. The mass deposited per unit area can be calculated using the cosine law of deposition ... 

Fig. 1. The ballistic interactions of an energetic ion with a sohd. Depicted are sputtering events at the surface, single-ion /single-atom recoil events, the development of a collision cascade involving a large number of displaced atoms, and the final position of the incident ion. ° = normal atom ...

When an energetic ion penetrates a soHd, it undergoes a series of coUisions with the atoms and electrons in the target. In these coUisions the incident particle loses energy at a rate of a few to 100 eV pet nanometer, depending on the energy and mass of the ion as well as on the substrate material. 

J. F. Ziegler, Handbook of Stopping Cross-Sectionsfor Energetic Ions in A.U Elements., Pergamon Press, New York, 1980. 

Sputtered Neutral Mass Spectrometry (SNMS) is the mass spectrometric analysis of sputtered atoms ejected from a solid surface by energetic ion bombardment. The sputtered atoms are ionized for mass spectrometric analysis by a mechanism separate from the sputtering atomization. As such, SNMS is complementary to Secondary Ion Mass Spectrometry (SIMS), which is the mass spectrometric analysis of sputtered ions, as distinct from sputtered atoms. The forte of SNMS analysis, compared to SIMS, is the accurate measurement of concentration depth profiles through chemically complex thin-film structures, including interfaces, with excellent depth resolution and to trace concentration levels. Genetically both SALI and GDMS are specific examples of SNMS. In this article we concentrate on post ionization only by electron impact. 

The atom flux sputtered from a solid surface under energetic ion bombardment provides a representative sampling of the solid. Sputtered neutral mass spectrometry has been developed as method to quantitatively measure the composition of this atom flux and thus the composition of the sputtered material. The measurement of ionized sputtered neutrals has been a significant improvement over the use of sputtered ions as a measure of flux composition (the process called SIMS), since sputtered ion yields are seriously affected by matrix composition. Neutral panicles are ionized by a separate process after sputter atomization, and SNMS quantitation is thus independent of the matrix. Also, since the sputtering and ionization processes are separate, an ionization process can be selected that provides relatively uniform yields for essentially all elements. 

Figura 1 Schematic of SNMS analysis. Neutral atoms and molecules sputtered from the sample surface by energetic ion bombardment are subsequently ionized for mass spectrometric analysis.

The essentials of SNMS are illustrated in Figure 1. The surface of the solid sample is sputtered by energetic ion bombardment. Generally, at eneigfes above a few hundred eV, several particles are ejected from the surface for each incident particle. A very small fraction of the particles are sputtered as ions, the so-called secondary ions... 

Fig. 4.47. Schematic diagram ofthe compensation mechanism to prevent charging ofthe sample surface when primary energetic ions and electrons are used.

Ion implantation consists of the injection of energetic ions beneath the surface of a material. Due to the high energy... 

The time-averaged potential profile is shown in Figure 4b. As ions cannot follow the oscillations in the applied electric field, it is this profile that ions experience. The bulk plasma is characterized by a constant potential, Vpi. In both sheaths (regions between plasma bulk and the electrodes), the ions experience a potential difference and are accelerated towards the electrodes. This leads to energetic ion bombardment of the electrodes. Electrons are expelled from the sheaths, so all ionization and dissociation processes must occur in the plasma bulk. Plasma light, resulting from emission from excited molecules, is emitted only from the plasma bulk the sheaths are dark. 

A simple model for a-C(N) H film growth kinetics was proposed [72], and was based on some aspects of the discussion developed in the previous subsection. The model is based on the incidence of only two species over a deposit, one representing C-carrying radicals and ions, while the other represents energetic ions. It is also based on the fact that C-containing radicals are the main channel for... 

NRA is a powerful method of obtaining concentration versus depth profiles of labelled polymer chains in films up to several microns thick with a spatial resolution of down to a few nanometres. This involves the detection of gamma rays produced by irradiation by energetic ions to induce a resonant nuclear reaction at various depths in the sample. In order to avoid permanent radioactivity in the specimen, the energy of the projectile is maintained at a relatively low value. Due to the large coulomb barrier around heavy nuclei, only light nuclei may be easily identified (atomic mass < 30). 

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