Atom-surface interactions, plasma

The plasma potential is the maximum value with which ions can be accelerated from the edge of the sheath towards the substrate, located at the grounded electrode. This may cause ion bombardment, which may induce ion-surface interactions such as enhancement of adatom diffusion, displacement of surface atoms, trapping or sticking of incident ions, sputtering, and implantation see Section 1.6.2.1. 

The main objective of this article is to summarize the work performed at the Max-Planck-Institute for Plasma Physics in Garching over the past few years relevant to plasma-surface interaction processes in the system hydrogen and carbon. This includes a short review of the properties of amorphous, hydrogenated carbon layers, further on abbreviated as a-C H, determination of reaction probabilities of reactive species such as atomic hydrogen and methyl radicals, and investigation of the simultaneous interaction of these species and low-energy ions with hydrocarbon surfaces. The reviewed ma-... 

We perform numerical modeling of atomic processes in various real plasmas including LHD fuel-pellet ablation and short-pulse laser interaction plasmas [21], We are developing a mixed quantum-classical code to study excited hydrogen atom formation in neutrals of back scattered protons at wall surfaces. 

Absorption spectroscopy and laser induced fluorescence (LIF), give access to the concentration of molecules, atoms, and ions in the ground state. LIF is enable to achieve highly spatial and time resolved analyses. This technique is thus particularly suitable to investigate composition changes in the plasma, and obtain spatial or time concentration profiles. Published results in fluorine plasmas using absorption [25-27] and LIF [28-32] mainly concern temperature measurements [25] or the quantification of CFV radicals [26-31] in fluorocarbon-based plasmas and SOx in SF6—02 discharges [32], Recently LIF has been used to measure plasma-surface interaction products [33]. 

The theory of van der Waals (vdW) surface interactions is presented here in terms of correlation-self energies of the constituent parts involved in the interaction due to their mutual polarization in the electrostatic limit. In this description the van der Waals interactions are exhibited using the dynamic, nonlocal and inhomogeneous screening functions of the constituent parts. In regard to the van der Waals interaction of a single molecule and a substrate, this problem is substantially the same as that of the van der Waals interaction of an atom and a substrate, in which the atomic aspects of the problem are subsumed in a multipole expansion based on spatial localization of the atom/molecule. As we (and others) have treated this in detail in the past we will not discuss it further in this paper. Here, our attention will be focussed on the van der Waals interaction of an adsorbate layer with a substrate, with the dielectric properties of the adsorbate layer modeled as a two-dimensional plasma sheet, and those of the substrate modeled by a semi-infinite bulk plasma. This formulation can be easily adapted to an... 

Fig. 13. Adsorption isotherms (left) and pore size distributions (right) computed from nitrogen (open squares) and argon (filled squares) adsorption at 77 K on a porous Saran char (top) and a granular activated carbon (bottom) [90]. (Reproduced with permission from S. Ramalingam. Plasma-surface interactions in deposition of silicon thin films An atomic-scale analysis. PhD Thesis, University of California, Santa Barbara 2000.)...

Several empirical and semiempirical interatomic potentials have been developed for the Si H systembased on extensions and modifications of well-known potentials for Si including up to three-body interactions (StilUnger and Weber, 1985 Biswas and Hamann, 1985 Biswas et al., 1987 Mousseau and Lewis, 1991 Baskes, 1992). Recent atomic-scale simulation work of plasma-surface interactions in the PECVD of Si thin films has been based on an empirical description of interatomic interactions in the Si H system according to Tersoff s (1986, 1988, 1989) potential for Si, as extended by Ohira and co-workers (1994, 1995, 1996) to incorporate Si-H, H-H, and the corresponding three-body interactions. The extension of the potential to include the presence of hydrogen adopted the Tersoff parametrization to fit results of ab initio calculations for the structure and energetics of Sil 1., x <4, species in the gas phase (Ohira et al., 1994,1995,1996). A similar form of... 

Maroudas, D., Ramalingam, S., and Aydil, E. S., Atomic-scale modeling of plasma-surface interactions in the PECVD of silicon. In Fundamental Gas-Phase and Surface Chemistry of Vapor-Phase Materials Synthesis, (Allendorf, M. D., Zachariah, M. R., Mountziaris, T. J., and McDaniel, A. H., Eds.), Electrochemical Society Proceedings Series, Vol. 98-23, Electrochemical Society, Pennington, NJ, 1999, pp. 179-190. 

Ramalingam, S., Plasma-Surface Interactions in Deposition of Silicon Thin Films An Atomic-Scale Analysis, Ph.D. thesis. University of California, Santa Barbara. 2000. 

The Springer Series on Atomic, Optical, and Plasma Physics covers in a comprehensive manner theory and experiment in the entire field of atoms and molecules and their interaction with electromagnetic radiation. Books in the series provide a rich source of new ideas and techniques with wide applications in fields such as chemistry, materials science, astrophysics, surface science, plasma technology, advanced optics, aeronomy, and engineering. Laser physics is a particular connecting theme that has provided much of the continuing impetus for new developments in the field. The purpose of the series is to cover the gap between standard undergraduate textbooks and the research literature with emphasis on the fundamental ideas, methods, techniques, and results in the field. 

Furthermore, clusters (i.e., aggregates of atoms or molecules) and particulates (i.e., small particles of solid) are also formed. The particulates thus formed may contaminate the base surface, influence plasma properties and structure, or have other undesirable consequences (Kushner, 1994). Furthermore, interactions of these particulates or of dust particles otherwise present are important to plasma properties and behavior therefore, they are a subject of extensive current research (Chutjian, 1999). 

During initiation of diamond nucleation, the substrate surface interacts chemically with the hydrocarbon-hydrogen plasma. Both carbon and hydrogen atoms penetrate the substrate. Metals form carbohydrides before diamond nucleation starts. Nucleation is initiated on such chemically modified surfaces. 

Thermal ionization. Takes place when an atom or molecule interacts with a heated surface or is in a gaseous environment at high temperatures. Examples of the latter include a capillary arc plasma, a microwave plasma, or an inductively coupled plasma. 

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