The present stage of development in microelec tronics poses increased requirements on the quality of thin films. The task of maintaining thorough control over their characteristics has become even more important in the case of thin complex conducting materials, the surface characteristics of which may strongly differ from their bulk properties. These differ ences, while insignificant for macroscopic samples, are of fundamental value for layers with thicknesses on the nanometer scale. For example, an analysis of the properties of complex oxides of transition metals (including cuprates [1], manganites [2], ferrites [3], etc.) in the conducting state showed that, even for the bulk material composition corresponding to the nom inal stoichiometry, the composition and structure of near surface layers can significantly vary, which leads to radical changes in their electrical and magnetic characteristics. The most frequently encountered defects in near surface layers of these materials are oxygen vacancies [4], the presence of which leads to the formation of a natural dielectric layer at the surface of conducting cuprates and manganites. This layer is a potential barrier for electrons tunneling from a metal electrode to complex oxides [5]. Since these oxides usually contain nanodimensional metal inclusions [6], electron transport in such systems frequently proceeds by charge carrier hopping between grains [2].The present investigation was aimed at developing a simple and effective approach to characterization of the microstructure of inhomogeneous near surface layers of conducting films with hopping conductivity. The proposed method is based on the creation of tun neling contacts on the film surface and an analysis of the influence of inelastic processes with phonon emis sion on the shape of the current-voltage characteristic I(V) of this heterostructure. Naturally, this approach is most applicable to materials with strong electronphonon interactions, such as high temperature cuprate superconductors in the normal state and man ganites [7]. In an interval of relatively low voltages V, where the surface barrier transparency weakly depends on the voltage sign and the distribution of defects is uniform, the inelastic contribution to the differential conductivity G(V) = dI(V)/dV is also independent of the sign of V and, hence, determines the even (with respect to voltage) contribution G (+) (V) = [G(V) + G(⎯V)]/2. The behavior of this even function will be considered below.The electron states in a dielectric barrier with cha otically distributed defects are usually localized and their wave functions exponentially decay at distances on the order of the localization length κ -1 . If the bar rier layer thickness d is greater than κ -1 , the main mechanism of conduction at sufficiently low temper atures is the hopping transport of charge carriers, whereby an electron jumps from one localized state to another (e.g., from state 1 to 2), which occur inside the barrier and are spaced by distance l (Fig. 1). Since the probability D of...