Direct measurement of transfer functions in Kelvin probe force microscopy using artificially patterned surface potentials

We report a direct measurement of two-dimensional (2D) transfer functions of conductive probes used in Kelvin probe force microscopy (KFM). The 2D transfer function, are obtained by measuring a well-defined step pattern Of surface potentials, prepared oil thin films of tris(8-hydroxyquinolinato)aluminum(III) (Alq(3)) by contact-mask exposure. The experimentally obtained 2D transfer functions are highly asymmetric and are spread over 50 mu m. A new finding is the observation of negative values in the KFM transfer function. which cannot be explained by conventional KFM formula. The reconstruction of true surface-potential profiles by model-fitting calculation is demonstrated. The technique presented in this study. i.e. the preparation of surface-potential patterns oil Alq(3) thin films, is ideal for determining the KFM transfer functions experimentally.