Invited: New characterization and fabrication techniques for the development of tunnel junctions like devices.

M. SIRENA; L. AVILÉS FÉLIX; L. B. STEREN; R. BERNARD; J. BRIATICO; N. BERGEAL; J. LESUEUR

Conferencia; 12nd Third world Academy of Science, ROLAC Young Scientists Conference; 2012

Research in the area of the nanostructures is today one of the most active in solid state physics. A tunnel junction consists of two conducting electrodes separated by a thin insulating layer in which the electrical transport occurs due to the tunnelling of the current carriers trough the barrier. The fabrication of tunnel junctions like devices (TJ) (such as magnetic tunnel junctions,   spin filters or even superconducting Josephson junctions) is of great importance for the study of various problems of fundamental physics (spin injection, proximity effect, etc.) and the development of new technological devices (magnetic sensors, SQUIDS, ultra high speed microelectronics, etc.). The fabrication of these structures is complicated and involves multiple steps of lithography, deposition and ion etching. It is then of great interest to have a simple method of fabricating these systems. In this presentation we?ll discuss the development of nano and microtemplates (NyMT) for the fabrication of TJ. One of the key factors in the fabrication of these systems is the quality of the insulating barrier. A phenomenological approach [1] is proposed to analyze the electrical transport through an insulating barrier in conducting/insulating bilayers, using conductive atomic force microscopy (CAFM). We have found that I(V) = A0 . VB , where A0 and B depend linearly with the barrier thickness. The proposed model allows to obtain critical information for the development of TJ. Moreover, assuming a Gaussian distribution of the barrier thickness, it is possible to fit the measured current distribution and to study the thickness homogeneity of the barrier. The influence of the substrate in the electrical properties of the ferromagnetic/ferroelectric bilayers was studied in the frame of this model. MgO substrates with higher roughness than SrTiO3 ones, were found to increase the barrier thickness distribution and to increase the attenuation length in the material, reducing the barrier quality for the developing of multiferroic tunnel junctions.    [1] M. Sirena, Journal of Applied Physics, 110, 063923 (2011).