A.J. Tosser

Bio: A.J. Tosser is an academic researcher. The author has contributed to research in topics: Electrical resistivity and conductivity & Temperature coefficient. The author has an hindex of 7, co-authored 16 publications receiving 221 citations.

A three-dimensional model for grain boundary resistivity in metal films

Abstract: In this work a model is proposed to express the resistivity of metal films in which two electron scattering mechanisms operate simultaneously: an isotropic background scattering and a scattering caused by three distributions of planar potentials which represent the grain boundaries. In order to describe the average properties of grain boundaries a transmission coefficient t is introduced. An interpretation of published fine-grained film data in terms of the three-dimensional model yields reasonable values of t .

Statistical model of electrical conduction in polycrystalline metals

Abstract: A new statistical model for the effect of grain boundaries on electrical conduction is proposed. The electronic transmission coefficient t is given as an exponential function of the electron path assuming that t ≈ 1. A mean free path related to grain boundary effects is then derived; the Boltzmann equation is solved using the assumption that background scattering and grain boundary scattering operate independently. The analytical expression of the total conductivity obtained in this way agrees with the Mayadas-Shatzkes equations.

Experimental determination of electronic transport parameters in monocrystalline metallic films

Abstract: New equations for the resistivity and temperature coefficient of resistivity (TCR) of monocrystalline films are derived from the theoretical predictions of the two-dimensional model previously proposed to describe the simultaneous scatterings due to the background, external surfaces and grain boundaries. It is found that the dependences of the film resistivity p Fm and TCR β Fm on the thickness a when they are plotted in the forms a p Fm and a β Fm -1 versus a should yield straight lines with slopes of p 0 and β 0 -1 respectively and an identical intercept on the ordinate of M ( t,p ). An analytical expression for M ( t,p ) as a function of the transmission coefficient t and the specularity parameter p is obtained which allows a systematic study of the changes in these parameters under various annealing and deposition conditions.

Hall coefficient of thin polycrystalline metallic films in a three-dimensional scattering model

Abstract: A three-dimensional grain boundary model can be used to calculate the transport properties of fine-grained films where background and grain boundaries scattering processes occur simultaneously. In the absence of a magnetic field a total relaxation time which is related to the grain size D and to the transmission coefficient t of electrons through grain boundaries is defined. Using the Boltzmann transport equation analytical expressions are easily derived for the Hall coefficient and conductivity in polycrystalline films subjected to a transverse magnetic field. The Hall coefficient is independent of both the grain parameters and the strength of the magnetic field whereas the film resistivity depends markedly on the grain size D and the transmission coefficient t. Some experimental data on polycrystalline films can be interpreted on the basis of these theoretical predictions.

Mean free path and effective density of conduction electrons in polycrystalline metal films

Abstract: The thickness dependence of the conductivity of copper, aluminium, silver, gold, nickel and platinum films was measured with high accuracy for various conditions of the evaporation. The Fuchs-Namba model was the only one which could be fitted to the experimental data. Four parameters were determined: σ∞, l ∞, p and h . The ratioσ∞/l∞ is not a constant of the material but depends on the crystallite size. The related effective electron density n ∞ is less than the value n b for bulk single-crystal material. The method employed allows us to separate to volume and surface effects on the conductivity as well as to separate the scattering of electrons inside the crystallites from the reflections of electrons by the crystallite boundaries.

Thermoelectric power of thin polycrystalline metal films in an effective mean free path model

Abstract: Starting from an effective Fuchs-Sondheimer conduction model, the theoretical expression for the thermoelectric power of polycrystalline metal films is derived. From the approximate expression for thick films, a procedure is proposed to determine the variation in the electronic mean free path.

Description of electronic transport properties of monocrystalline films by a statistical model

Abstract: Grain boundaries in monocrystalline films are represented by a two- dimensional array of scatterers. The effects of electronic scattering are calculated by means of Matthiessen's rule starting from the electronic mean free path related to a particular type of scattering (bulk, grain boundary, external surface). Theoretical expressions for the film resistivity and its temperature coefficient of resistivity and thermoelectric power are proposed; comparison with previously reported experiments gives a satisfactory fit.

Mechanisms of adsorbate-induced surface resistivity––experimental and theoretical developments

Abstract: Recent experimental and theoretical developments in explaining adsorbate effects on electronic conduction in metals are critically reviewed. These effects are of more than academic interest, with applications in nanotechnology, chemical sensing, and tribology. The prevailing model treats the metal as a free-electron gas and the adsorbates as independent point scatterers. This model, first developed by Fuchs and Sondheimer and elaborated in recent years by Persson and Volokitin, makes specific quantitative predictions regarding the optical effects of surface resistivity. Some have been accurately verified, including the spectral shape and temperature dependence of the adsorbate-induced reflectance change, and anti-absorption resonances associated with dipole-forbidden vibrations. The model also predicts, however, that the ratio of the adsorbate-induced reflectance and resistivity changes should depend only on the properties of the metal, and not on those of the adsorbate, and this prediction is strongly violated in several recent experiments. Possible explanations of the discrepancy are discussed.

A theoretical model for the electrical properties of chromium thin films sputter deposited at oblique incidence

Abstract: Chromium thin films are prepared by magnetron sputtering using the glancing angle deposition (GLAD) method. The electrical conductivity of the films exhibiting an inclined columnar structure is investigated. An analytical three-dimensional model is proposed in order to predict the evolution of the electrical conductivity as a function of the columns' orientation. This model is based on two types of electron scattering mechanisms, which are simultaneously operational: the isotropic background scattering at the grain boundary and the scattering due to electron dispersion at the column boundary. The developed analytical expressions enable systematic studies of different processes and film parameters, especially the column angle β as well as the sputtering pressure used during the GLAD deposition. The theoretical and experimental results are compared. It is found that the column angle β must reach a threshold value to significantly reduce the electrical conductivity of chromium thin films close to one order of magnitude. The effect of the sputtering pressure on the structure of films and their electrical behaviours are also studied and well predicted by the proposed model. Finally, a comprehensive discussion of the applicability of the model is presented.