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Absence of Evidence for Fixed Charge in Metal-Aluminum Oxide-Silicon Tunnel Diodes
摘要： Here, a controlled variation in the fixed charge density (NF) and thickness of aluminum oxide tunnel insulators is reported, and the impact on Schottky barrier height ΦB in metal–insulator–semiconductor (MIS) diodes is studied. Analysis of metal–aluminum oxide–silicon capacitor structures indicates a change in NF from t1 × 1012 cm?2 in as-deposited films to ?1 × 1012 cm?2 in annealed films. An analytical model and numerical device physics simulations are used to predict changes in ΦB based on these changes in NF and alumina thickness. Surprisingly, Mott–Schottky derived ΦB values did not follow the trends predicted by these electrostatic models. In fact, there seems to be no discernable effect of NF in diodes with alumina thicknesses below 2 nm, contrary to contactless measurements of the fixed charge of films of similar thickness. The ΦB trends are better explained by a dipole model. It is further shown that in as-deposited MIS diodes, the dipole is a function of alumina layer thickness, whereas in annealed MIS diodes, the dipole and ΦB were roughly constant independent of alumina thickness. These data suggest a strategy by which the ΦB of MIS tunnel contacts can be controlled and which has implication for the design of electrical contacts.
关键词： atomic layer deposition,fixed charges,silicon,barrier height,Schottky diodes
更新于2025-09-23 15:21:01
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Bifurcation of finitely deformed thick-walled electroelastic spherical shells subject to a radial electric field
摘要： This paper is concerned with the bifurcation analysis of a pressurized electroelastic spherical shell with compliant electrodes on its inner and outer boundaries. The theory of small incremental electroelastic deformations superimposed on a radially finitely deformed electroelastic thick-walled spherical shell is used to determine those underlying configurations for which the superimposed deformations do not maintain the perfect spherical shape of the shell. Specifically, axisymmetric bifurcations are analyzed, and results are obtained for three different electroelastic energy functions, namely electroelastic counterparts of the neo-Hookean, Gent and Ogden elastic energy functions. For the neo-Hookean energy function it was reported previously that for the purely mechanical case axisymmetric bifurcations are possible under external pressure only, no bifurcation solutions being possible for internally pressurized spherical shells. In the case of an electroelastic neo-Hookean model bifurcation under internal pressure becomes possible when the potential difference between the electrodes exceeds a certain value, which depends on the ratio of inner to outer undeformed radii. Results obtained for the three classes of model are significantly different and are illustrated for a range of fixed values of the potential difference. Although of less practical significance, results are also shown for fixed charges, and these are both different between the models and different from the case of fixed potential difference.
关键词： neo-Hookean,Ogden,spherical shell,potential difference,Gent,fixed charges,electroelastic,bifurcation
更新于2025-09-16 10:30:52