In four-probe (4-probe) electrical measurements, especially on highly resistive materials, it is not always possible to configure the electrodes such that the current density is uniform throughout the sample. Under such circumstances, simply considering the material's electrical resistivity to be proportional to the measured resistance with the proportionality constant given by the sample geometry can give an incorrect result. In this paper, a numerical finite element model is presented which can extract a material's true resistivity from co-linear 4-probe electrical measurements on highly resistive samples with large electrodes that extend across the sample width. The finite element model is used to investigate the influence of material anisotropy, the resistance of the sample-electrode interfaces and the relative electrode-to-sample size on the potential and current density distributions in the sample. A correction factor is introduced to account for the impact of these effects on the measured resistivity. In the limit of large interface resistance, excellent agreement is found with an analytical expression derived elsewhere (Esposito et al 2000 J. Appl. Phys. 88 2724. The approach presented here can be used to evaluate a variety of effects on co-linear 4-probe electrical measurements, can be extended to complex specimen geometries with arbitrary electrode arrangements and, additionally, could find use in the evaluation of data from 4-probe thermal conductivity measurements.
On behalf of the Editorial Board we introduce the first issue of the Journal of Nanoengineering and Nanosystems, Part N of the Proceedings of the Institution of Mechanical Engineers. After a thorough overview of nanotechnology the editors decided that the field of nanoengineering (with an emphasis on nanosystems) should be the focus of a new journal.It has become obvious that nanotechnology will play a central role in the wide-ranging and rapid development of the scientific and technological knowledge base. The era of 'nanosystems engineering' is emerging, which calls for an adequate forum for discussing the assembly of more complex systems containing several or many interacting components. The study of nanosystems is clearly interdisciplinary and one of the purposes of the Journal of Nanoengineering and Nanosystems is to present important cross-disciplinary research on nanosystems and engineering issues associated with them. Manuscripts are welcomed from specialists in any of the scientific or engineering disciplines, and from teams representing many disciplines.
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