Evaluation of physical parameters of localized states in insulating Y-Ba-Cu-O layers by means of electronic transport measurements

Electronic transport measurements were carried out on YBa2Cu3O7−δ/insulator/Au planar junctions in order to determine physical parameters of the localized states in thin insulating Y-Ba-Cu-O layers. In doing so, 12×5 μm2 YBa2Cu3O7−δ/insulator/Au junction areas were defined by standard lithographic techniques and Ar ion milling. The analysis of the conductance of the junction at high-temperature or high-bias voltages showed that Mott's variable-range hopping conduction model is appropriated to describe the electrical behavior of the junction in this regime. From the fitting procedure, important physical parameters of the barrier such as the localization length α−1 (∼3 Å), the average barrier height φ (∼0.5 eV) or the variable range hopping length ℓin (∼20 Å at ∼300 K) were estimated. The experimentally estimated values were physically reasonable and comparable to those reported for other oxide materials.