The intrinsic stress of polycrystalline and epitaxial thin metal films
TL;DR: In this article, a thorough discussion of today's understanding of the growth of thin metal films and related atomistic mechanisms responsible for intrinsic stress is presented, where the intrinsic stress either originates from strained regions within the films (grain boundaries, dislocations, voids, impurities, etc.) or at the film/substrate (lattice mismatch, different thermal expansion, etc).
Abstract: It is well known that thin films develop large intrinsic stress during their preparation. The intrinsic stress either originates from strained regions within the films (grain boundaries, dislocations, voids, impurities, etc.) or at the film/substrate (lattice mismatch, different thermal expansion, etc) and film/vacuum interfaces (surface stress, adsorption, etc.) or is due to dynamic processes (recrystallization, interdiffusion, etc). Since the magnitude of most of these stress contributions is directly related to film morphology, important structural information can be extracted from measurements of the intrinsic stress. This article presents a thorough discussion of today's understanding of the growth of thin films and reviews the related atomistic mechanisms responsible for intrinsic stress. On the basis of these ideas recent experimental results on the intrinsic stress of UHV deposited polycrystalline and epitaxial thin metal films are discussed. Depending on the respective growth mode of the films-Volmer-Weber, Stranski-Krastanov and Frank-Van der Merwe modes-characteristic stress behaviours are observed. In situ intrinsic stress measurements are therefore a promising new technique to gain additional insight into film growth.
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02 Feb 2004TL;DR: The role of stress in mass transport is discussed in this article, where the authors consider anisotropic and patterned films, buckling, bulging, peeling and fracture.
Abstract: 1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.
1,562 citations
TL;DR: In this article, the authors discuss sensors with transducers in a form of cantilevers, which are especially attractive as transducers for chemical and biological sensors, and provide a brief analysis of historical predecessors of the modern cantilever sensors.
Abstract: Since the late 1980s there have been spectacular developments in micromechanical or microelectro-mechanical (MEMS) systems which have enabled the exploration of transduction modes that involve mechanical energy and are based primarily on mechanical phenomena. As a result an innovative family of chemical and biological sensors has emerged. In this article, we discuss sensors with transducers in a form of cantilevers. While MEMS represents a diverse family of designs, devices with simple cantilever configurations are especially attractive as transducers for chemical and biological sensors. The review deals with four important aspects of cantilever transducers: (i) operation principles and models; (ii) microfabrication; (iii) figures of merit; and (iv) applications of cantilever sensors. We also provide a brief analysis of historical predecessors of the modern cantilever sensors.
1,165 citations
TL;DR: High power pulsed magnetron sputtering (HPPMS) is an emerging technology that has gained substantial interest among academics and industrials alike as discussed by the authors, also known as HIPIMS (high power impulse...
Abstract: High power pulsed magnetron sputtering (HPPMS) is an emerging technology that has gained substantial interest among academics and industrials alike. HPPMS, also known as HIPIMS (high power impulse ...
846 citations
TL;DR: The role of surface stress at solid surfaces in a vacuum environment and in contact with a liquid electrolyte in reconstruction, epitaxial growth and self-organization or stabilization of mesoscopic structures is critically reviewed in this paper.
705 citations
TL;DR: In this paper, the authors examined the stress associated with crystallite coalescence during the initial stages of growth in thin polycrystalline films with island growth morphology and predicted large tensile stresses in agreement with experimental results.
Abstract: We examined the stress associated with crystallite coalescence during the initial stages of growth in thin polycrystalline films with island growth morphology. As growing crystallites contacted each other at their bases, the side-walls zipped together until a balance was reached between the energy associated with eliminating surface area, creating a grain boundary and straining the film. Our estimate for the resulting strain depends only on interfacial free energies, elastic properties, and grain size and predicts large tensile stresses in agreement with experimental results. We also discuss possible stress relaxation mechanisms that can occur during film growth subsequent to the coalescence event.
554 citations
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TL;DR: It is well known that metallic films deposited electrolytically are in many cases liable to peel off if deposited to any considerable thickness as discussed by the authors, especially if it does not adhere very tightly to the body on which it is deposited.
Abstract: It is well known that metallic films deposited electrolytically are in many cases liable to peel off if deposited to any considerable thickness. This is the case with nickel which, when deposited over a certain thickness, will curl up into beautiful close rolls, especially if it does not adhere very tightly to the body on which it is deposited. For example, if a piece of glass is silvered by any of the usual silvering solutions, and then nickel is deposited on the silver, it is found that the nickel and silver peel off the glass in close tight rolls almost at once. In ‘Practical Electro-Chemistry,' by Bertram Blount, reference is made on pp. 114 and 272 to the tendency of nickel to peel off, and it is stated that it “will peel—spontaneously and without assignable cause” (p. 272), but that a thick coating can be obtained by keeping the solution at between 50° and 90°C. The late Earl of Rosse tried, about 1865, to make flat mirrors by coating glass with silver chemically, and then electroplating with copper; but he found that, owing to the “contraction” of the copper film, it became detached from the glass. I have had the' same experience in protecting silver 61ms in searchlight reflectors by a film of electro-deposited copper, it being found that if the film of copper is more than 0.01 mm. thick peeling is apt to take place.
4,477 citations
12 Jun 1951-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this paper, it was shown that the rate of growth of a surface containing dislocations is proportional to the square of the supersaturation for low values and to the first power for high values of the latter.
Abstract: Parts I and II deal with the theory of crystal growth, parts III and IV with the form (on the atomic scale) of a crystal surface in equilibrium with the vapour. In part I we calculate the rate of advance of monomolecular steps (i.e. the edges of incomplete monomolecular layers of the crystal) as a function of supersaturation in the vapour and the mean concentration of kinks in the steps. We show that in most cases of growth from the vapour the rate of advance of monomolecular steps will be independent of their crystallographic orientation, so that a growing closed step will be circular. We also find the rate of advance for parallel sequences of steps. In part II we find the resulting rate of growth and the steepness of the growth cones or growth pyramids when the persistence of steps is due to the presence of dislocations. The cases in which several or many dislocations are involved are analysed in some detail; it is shown that they will commonly differ little from the case of a single dislocation. The rate of growth of a surface containing dislocations is shown to be proportional to the square of the supersaturation for low values and to the first power for high values of the latter. Volmer & Schultze’s (1931) observations on the rate of growth of iodine crystals from the vapour can be explained in this way. The application of the same ideas to growth of crystals from solution is briefly discussed. Part III deals with the equilibrium structure of steps, especially the statistics of kinks in steps, as dependent on temperature, binding energy parameters, and crystallographic orientation. The shape and size of a two-dimensional nucleus (i.e. an ‘island* of new monolayer of crystal on a completed layer) in unstable equilibrium with a given supersaturation at a given temperature is obtained, whence a corrected activation energy for two-dimensional nucleation is evaluated. At moderately low supersaturations this is so large that a crystal would have no observable growth rate. For a crystal face containing two screw dislocations of opposite sense, joined by a step, the activation energy is still very large when their distance apart is less than the diameter of the corresponding critical nucleus; but for any greater separation it is zero. Part IV treats as a ‘co-operative phenomenon’ the temperature dependence of the structure of the surface of a perfect crystal, free from steps at absolute zero. It is shown that such a surface remains practically flat (save for single adsorbed molecules and vacant surface sites) until a transition temperature is reached, at which the roughness of the surface increases very rapidly (‘ surface melting ’). Assuming that the molecules in the surface are all in one or other of two levels, the results of Onsager (1944) for two-dimensional ferromagnets can be applied with little change. The transition temperature is of the order of, or higher than, the melting-point for crystal faces with nearest neighbour interactions in both directions (e.g. (100) faces of simple cubic or (111) or (100) faces of face-centred cubic crystals). When the interactions are of second nearest neighbour type in one direction (e.g. (110) faces of s.c. or f.c.c. crystals), the transition temperature is lower and corresponds to a surface melting of second nearest neighbour bonds. The error introduced by the assumed restriction to two available levels is investigated by a generalization of Bethe’s method (1935) to larger numbers of levels. This method gives an anomalous result for the two-level problem. The calculated transition temperature decreases substantially on going from two to three levels, but remains practically the same for larger numbers.
4,432 citations
Abstract: A model for random aggregates is studied by computer simulation The model is applicable to a metal-particle aggregation process whose correlations have been measured previously Density correlations within the model aggregates fall off with distance with a fractional power law, like those of the metal aggregates The radius of gyration of the model aggregates has power-law behavior The model is a limit of a model of dendritic growth
4,248 citations
TL;DR: In this article, the theory of a one-dimensional dislocation model is developed, and critical conditions for spontaneous generation (or escape) of dislocations are determined, and also the activation energies for such processes below the critical limits.
Abstract: The theory of a one-dimensional dislocation model is developed. Besides acting as a pointer to developments of general dislocation theory, it has a variety of direct physical applications, particularly to monolayers on a crystalline substrate and to conditions in the edge row of a terrace of molecules in a growing crystal. Allowance is made in the theory for a difference in natural lattice-spacing between the surface layer or row and the substrate. The form and energy of single dislocations and of regular sequences of dislocations are calculated. Critical conditions for spontaneous generation (or escape) of dislocations are determined, and likewise the activation energies for such processes below the critical limits. Various physical applications of the model are discussed, and the physical parameters are evaluated with the aid of the Lennard-Jones force law for the above-mentioned principal applications.
1,105 citations
TL;DR: In this paper, the fundamental nature of the internal stresses that are found in both evaporated and sputtered coatings is reviewed from the point of view of decorative coating applications, which indicate that apparatus geometry is particularly important in determining the state of stress that forms in deposits.
1,096 citations