Tunnel transport through CoFe₂O₄ barriers investigated by conducting atomic force microscopy

Abstract

Conducting atomic force microscopy has been used to monitor the quality of spin-filtering CoFe 2 O 4 tunnel barriers by mapping current as a function of their thickness. We show that appropriate film annealing leads to a substantial improvement of their tunnelling properties. The contact force between tip and sample was identified to have a determining influence on the width of the distribution P(I) in current maps, thus precluding its reliable use to infer barrier characteristics. Therefore, assessment of tunnel transport should be done by means of the typical current which is a well defined parameter at a given contact force, rather than by the current distribution width.

Structural and transport characterization of ultra thin Ba0.05Sr0.95TiO3 layers grown over Nb electrodes for the development of Josephson junctions

“…(2)). This has already been observed for spin filter barriers 9 and has been ascribed to an experimental artifact originated in the influence of the tip pressure during the measurement and when using the width of the current distribution to calculate k. The authors conclude that a more reliable method to calculate the attenuation length is to use the decrease of the mean current as a function of the barrier thickness. It is not clear that this is the origin of the observed behavior in our case.…”

“…However, even if important research has been done regarding the development of magnetic tunnel junctions [6][7][8] and spin filters, 9 very little work has been done in the study and characterization of insulating barriers for the development of Josephson junctions using CAFM. 10 The characteristics of the barrier, e.g., roughness, energy, and the attenuation length of the current, depend on the electronic properties of the electrodes.…”

High transition temperature superconductor/insulator bilayers for the development of ultra-fast electronics

“…The samples present roughness values smaller than 1 nm, with an extremely low density of surface defects ($5 Â 10 À5 defects/lm Tunnel junctions (TJ) like devices typically consist of two conducting electrodes separated by a thin insulating barrier, in which the current flows in the direction perpendicular to the surface. TJ present a wide range of applications, going from spintronics (magnetic tunnel junctions, 1 spin filters, 2 etc.) to superconducting electronics using Josephson junctions (JJ) 3 or even molecular junctions.…”

Nontunnel transport through CoFe2O4 nanometric barriers

“…Then a thin CFO barrier ͑thickness t =2-8 nm͒ was deposited on top of SRO. 13 Additionally, for series 2 samples, small Pt contacts ͑with area A ϳ3-30 m 2 ͒ were prepared on top of the CFO by electron beam induced deposition. The detailed deposition conditions are reported elsewhere.…”

“…1 the dependence of the measured current on the CFO thickness is shown. These values were obtained from current density distributions P͑J͒ determined from current maps 13 ear slope of the measured J-V curves at low bias voltages ͑examples are shown in Fig. 1͑a͒ were measured on Pt contacts on samples of series 2.…”