Emission observation of a microtip cathode array with an electrostatic-lens projector: Statistical approach

We report results on the field emitters' electrical properties uniformity, directly measured by an electrostatic-lens projector apparatus. First, we describe the experimental setup and its resolution capability. Then, we present the emission characteristics of two 1 mm(2) microtip arrays measured in ultrahigh vacuum and we compare these characteristics to the results of a numerical approach by taking into account a Gaussian distribution of beta (the tip sharpness). From these experimental data, fitted by a numerical description of the probably emitting tips, it is possible to deduce the mean and the standard deviation of tip sharpness in our samples. A comparison between these experiments and microtip atomic force microscopy characterizations coupled to field-emission simulations, shows a good agreement. Finally, we show the effect of hydrogen on the tips' emissive properties by using the standard Fowler-Nordheim analysis and we explore the induced changes on their statistical emission characteristics. All these results show that the probability density function of the emitting tips with respect to the applied voltage is uniform and very close to a top-hat function. (C) 1998 American Vacuum Society. [S0734-211X(98)05902-2].