I.V. Katardjiev

The application of the Huygens principle to surface evolution in inhomogeneous, anisotropic and time-dependent systems

A general approach to continuum wavefront motion in anisotropic, inhomogeneous and time-dependent systems based on the Huygens principle of wave propagation is presented. The fundamental nature of the elementary Huygens wavelet is discussed and its derivation also presented. Specific examples of surface evolution during anisotropic chemical etching, ion bombardment-induced erosion and curvature-dependent wavefront propagation are considered as illustrations of the general approach.

XPS STUDY OF ION BEAM IRRADIATION EFFECTS IN POLYIMIDE LAYERS

Abstract Thin polyimide films deposited on silicon or metal covered glass-ceramic substrates were exposed to ion bombardment at different fluences ranging from 1 × 1012 to 1.5 × 1016 cm−2. The XPS technique was used to study the polymer stoichiometry of the near surface layers (∼ 75 A) before and after the bombardment. The results show that the stoichiometric ratio of O, N and C-groups remains approximately constant with depth for unirradiated samples. A relative enrichment of C (probably in phenyl or CHx groups) occurred in the implanted samples. Scission of Cue5f8N and C=O bonds was observed, the latter being complete at doses above 1014 cm−2. Desorption of O and N was also found.

An altered layer model for ion assisted deposition under net growth conditions

Abstract A model for ion assisted deposition under net growth conditions is proposed and analyzed. Separate fluxes of depositing atoms and energetic ions are assumed, the role of the latter being to directly implant into the growing film structure, to intermix all atoms in the structure and to sputter from the surface. A three layer plus bulk substrate is assumed in which deposit and energetic atoms can trap in, be sputtered from and mixed inwards from an outer sputter layer. This second layer traps energetic atoms and receives atoms from and delivers atoms to the sputtering layer by atomic intermixing processes stimulated by the energetic particle flux. The third, deeper layer is where such processes have operated but subsequently terminated. The analysis reveals the importance of incident fluxes, stopping, mixing and sputtering processes in determining the different atomic constituent concentrations in these layers.

The influence of thermal relaxation on implantation induced disorder accumulation

Abstract A detailed analysis is made of disorder accumulation under direct ion implantation amorphous zone generation conditions where the zone size can thermally relax both during and after implantation. It is shown that this leads to considerable complexity in the behaviour of the amorphous fractionf as a function of ion fluence Φ, ion flux densityJ and substrate temperatureT. Steady state and low amorphous fraction solutions show how zone expansion or contraction processes can be distinguished.

Analytic, geometric and computer techniques for the prediction of morphology evolution of solid surfaces from multiple processes

The morphology of surfaces, depending on the nature of their environment, may be altered by erosional and/or accretional processes. Analytic description of the changing topography is possible through a knowledge of a locally variable parameter, which is the surface motion velocity in an arbitrarily specified direction. For sputter-related processes in which this parameter is spatially and temporally invariant over specific regions of a surface (e.g. ion milling, reactive-ion etching), the evolution of those regions may be forecast by geometric methods. Inhomogeneity of this parameter, which would generally result from the secondary and tertiary effects of ion irradiation, tenders evolution predictable only by iterative computer techniques. This paper summarises the status of analytic, geometric and computer methods of macroscopic surface simulation and notes the suitability of computer methods for simulation at the atomic scale.

Fundamental irradiation processes relevant to plasma-surface technology

Abstract Plasma-surface technology is becoming increasingly widely used for both controlled growth and erosion of solids. The interactions between the plasma and a surface include irradiation of the latter with a range of projectiles including atoms, ions, electrons and photons. This review examines the important fundamental processes which occur during irradiation with these species separately and in synergism.

Reproducibility and stability in surface morphological evolution

Abstract The steady-state surface morphology of solids under conditions of constant-volume thermodynamic equilibrium or the self-similar reproducible morphology during kinetically driven growth or erosion are reviewed. These considerations are used to develop the general requirements for steady-state reproducible morphological evolution when both kinetic and the thermodynamic processes operate. Several specific applications of the analysis, including ion-bombardment sputtering or atomic deposition both mediated by surface atomic diffusion, are explored.

The deduction of ballistic atomic mixing rates from high fluence ion implant collection depth distributions

Abstract An analysis is made, based upon differential atomic transport fluxes in a substrate resulting from implant ion collection, ballistically stimulated atomic relocation or mixing and surface sputtering, of the evolution of equivalent atom concentration-depth profiles in a substrate as a function of increasing ion flux. It is then shown how carefully controlled experimental studies of such profiles can be deconvoluted to determine interlayer atomic mixing probability distributions. The relevance of such an approach to sputter profiling of equivalent atom impurity profiles in a substrate is explored.

Simulation of erosion induced surface evolution in temporally and spatially dependent systems

Abstract A concise objective and critical survey of the theoretical and numerical approaches to surface evolution during ion bombardment is made. The strengths, limitations and deficiencies of these approaches are briefly discussed and the necessity of further development is outlined. A generalization of the wave approach to surface evolution based on the Huygens principle of wavefront propagation is made. A new robust numerical algorithm developed on the same basis is used for simulation of erosion induced surface evolution under temporally and spatially dependent conditions.

Sputtering-induced surface topography on F.C.C. metals

Abstract High fluence ion implantation of solids is known both to lead to new phase evolution and to modify, by sputtering, the surface topography of the solid. In the past the two processes have been separated by the use of only intermediate, but variable species, fluences in the former (e.g. by mixing of two-layer systems) or high fluence, inert gas or self-iron irradiation in the latter type of study. In the present study a variety of very high fluence (greater than 10 19 ions cm −2 ) implants into polycrystalline and single-crystal copper substrates have been studied to elucidate both mixing (and possible phase formation) and topographic evolution effects. The species were chosen to exert similar ballistic or collisional processes but different chemical or metallurgical effects in the substrate.