The use of Simmons’ equation to quantify the insulating barrier parameters in Al/AlOx/Al tunnel junctions

Abstract

We have analyzed the electron transport processes in Al/AlOx/Al junctions. The samples were produced by glow-discharge-assisted oxidation of the bottom electrode. The nonlinear I–V curves of 17 samples were measured at room temperature, being very well fitted using the Simmons’ equation with the insulating barrier thickness, barrier height, and the junction area as free parameters. An exponential growth of the area normalized electrical resistance with thickness is obtained, using just values from I–V curve simulations. The effective tunneling area corresponding to the “hot spots” can be quantified and is five orders of magnitude smaller than the physical area in the studied samples.

Microscopic origin of critical current fluctuations in large, small, and ultra-small area Josephson junctions

“…Indeed, it is difficult to imagine microscopic processes that affect large areas ∼ 10nm 2 ; a more plausible explanation is that the conductance is dominated by relative small areas or channels in this system [16] which decreases further the number of fluctuators (Figure 1). This conjecture is supported by the recent analysis [17] that found that the conductive area is κ ∼ 10 −5 of the total. Most likely, however, this value depends strongly on the material preparation.…”

Experimental determination of tunneling characteristics and dwell times from temperature dependence of Al/Al2O3/Al junctions

“…This oxidation method was preferred given its lowest oxidation rate as compared with more sophisticated methods, such as oxygen plasma and dry oxygen methods. The former may lead to shorts and pinholes or "hot spots," 11,12 and the latter compared with the present work does not produce a more robust oxide layer as will be discussed later.…”

“…These may even occur in experiments where advanced plasma oxidation techniques have been used. 11,12 The present work focuses on the temperature dependence of the tunneling phenomena across Al 2 O 3 . We find no appreciable variation of the barrier width as a function of temperature and a mild temperature dependence of the barrier height.…”

Atomically Thin Al2O3 Films for Tunnel Junctions

“…One line fit the band gap regime, and the other the conduction band. This ln(dI/dV) linear fit method was chosen over IV or (dI/dV)/(I/V) fit methods for it's insensitivity to high noise in STS spectra [14,15]. Approximately 40-80 dI/dV spectra were taken on each sample >100 nm apart from one another in order to get reasonable statistics on the sample's surface.…”