Uniform description of errors in measurement and evaluation of Langmuir probe characteristics by means of apparatus functions

摘要

The evaluation of Langmur probe measurements frequently has to deal with distortions of the probe current or its derivatives which occur e.g. in rf-discharges or in the differentiation of probe characteristics with electrical or numerical techniques. Using different methods it was shown that the distorted current or derivative is given by the convolution of the desired true function with an apparatus function. This contribution summarizes the treatment of the problem based on the fact that all distortions are caused by the superposition of additional voltages to the steady probe bias. This uniform behaviour allows a uniform treatment. In contrast to literature here separate apparatus functions for distortions caused by rf- oscillations are obtained. Examples of apparatus functions are shown for all kinds of distortions. Some applications of apparatus functions and a measuring example are given and a modified evaluation of the probe characteristic at incomplete rf-compensation is proposed.