| Abstract: | The curvature seen in Child's law plots of current-voltage characteristics measured using plane parallel diodes may be analysed in a number of ways to give information about the work function distribution of a cathode. This paper suggests a simple technique for characterising a cathode based on the assumption it has a “top-hat” work function distribution. The technique allows synthetic current/voltage characteristics to be generated which agree well with the practical characteristics from which the parameters of the work function distribution were derived. The parameters of the “top-hat” model may also be used to obtain an equivalent Gaussian work function distribution which gives almost identical synthetic characteristics and Schottky enhancement may be modelled in a rather empirical manner. Since either model gives good predictions, synthetic characteristics may be used to investigate other methods used to characterise cathodes. It is found that there is generally reasonable agreement which could be improved, for most practical work function distributions, by the choice of parameters slightly different from those normally used. |
