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The letter investigates the enhanced thermal oxidation of tantalum using oxygen-ion implantation. A comparison of the electrical and dielectric properties is made between the oxygen-implanted thermal oxides and of those fabricated without implantation. The ion-implanted tantalum-oxide films are shown to be superior to the unimplanted layers for the fabrication of oxide capacitors.

The density of anodically formed thin films on sputtered tantalum has been measured in situ. The method used is the measurement of the average density of the assemblage tantalum‐tantalum oxide and subsequent separation of the contributions of each component to this measured density. From a knowledge of the stoichiometry of the reaction, both the thickness and the angstrom per volt values (thickness of oxide formed per volt) can be determined for the oxide. Application of the capacitance formula for a parallelplate capacitor leads to a value for η. The values obtained are: Density; ; anodization constant, ; dielectric constant, at 1 kcps.

The effect on the cross-capacitances per unit length of cylindrical 3-terminal capacitors of thin dielectric films on the capacitor electrodes is discussed. It is assumed that the cross-section of such dielectric films remains constant throughout the length of the capacitor. Some conformal transformations of basic cylindrical capacitor cross-sections are given. When these are applied to a symmetric cylindrical capacitor with a thin dielectric film on its electrodes, the results suggest that the mean capacitance per unit length may remain constant to the first order despite the presence of the dielectric film. The same methods also suggest that the individual cross-capacitances per unit length may remain constant to the first order provided that the dielectric film is disposed symmetrically with respect to the capacitor symmetry plane. Further support for these conjectures is given by the results of a detailed calculation of the cross-capacitances per unit length of a parallel-plate cylindrical capacitor with a thin uniform dielectric film on one electrode. In the last Section, a lemma concerning the existence of an equivalent dielectricless capacitor is given and this is followed by the proof of general results of the type suggested by the previous working.

A transmission-line treatment has been used to explain the variation of capacitance and dissipation factor of cylindrical porous-anode bodies as a function of frequency due to the distributed resistance of the electrolyte within the pores. A correction has been determined to account for the effect of the ends of the cylindrical body. An effective resistivity is determined from experimental results which is a function of rhe volume of either the solid or liquid electrolyte and is also a function of the proportion of closed pores. A packed-sphere model is used to indicate the effect of the mean metal-particle size. The theory is applied to experimental results on a tantalum electrolytic capacitor.

Starting with the known but unexplained fact that high‐voltage electrolytic capacitors need operating electrolytes of high resistivity, breakdown (sparking) voltages of aluminum and tantalum anodes have been examined. If interfering side reactions are eliminated, breakdown voltage increases linearly with the logarithm of electrolyte resistivity and is insensitive to variations in electrolyte composition and to changes in temperature between 65°C and 95°C.

The various stages in the production of an aluminium electrolytic capacitor are outlined and these are then related to the equivalent circuit so as to establish an understanding of the preparation parameters that affect the performance. Particular reference is made to studies undertaken on the effects of etching prior to anodization, the anodization itself, the electrolyte used and the mechanical construction. In the case of sintered porous tantalum electrolytic capacitors, the parameters are not so well understood but comparisons will be drawn with aluminium capacitors wherever possible.