Fabrication of stable and reproducible submicron tunnel junctions (original) (raw)
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Journal of Nanomaterials, 2017
We present a versatile nanodamascene process for the realization of low-power nanoelectronic devices with different oxide junctions. With this process we have fabricated metal/insulator/metal junctions, metallic single electron transistors, silicon tunnel field effect transistors, and planar resistive memories. These devices do exploit one or two nanometric-scale tunnel oxide junctions based on TiO2, SiO2, HfO2, Al2O3, or a combination of those. Because the nanodamascene technology involves processing temperatures lower than 300°C, this technology is fully compatible with CMOS back-end-of-line and is used for monolithic 3D integration.
IEEE Transactions on Magnetics, 1981
We have fabricated a variety of small-area, superconducting tunnel junctions and simple superconducting interferometer circuits using novel e-beam and optical lithographic techniques. These Pb-oxide-Pb(1n) tunnel junctions are made using selfaligning processes which involve multiple oblique evaporations through suspended liftoff stencils formed in two-layer resist systems. Oxide barriers are grown in situ immediately after evaporation of base electrode films. Junction areas range from cm2 (optically patterned) to about cm2 (e-beam patterned). Current densities as high as 2x11)~ A/cmZ have been attained. The high current-density junctions show only small hysteresis at 4K and are completely non-hysteretic at higher temperatures. These junctions have been used to make lowhysteresis interferometers with a current gain of 3. A positive feedback scheme is described which provides sharper switching characteristics in non-latching interferometers.
Applied Physics Letters, 2003
We have analyzed the electron transport processes in Al/AlO x /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.
Effect of ion-milled barriers on electron transport in micrometer-sized tunnel junctions
Journal of Physics D: Applied Physics, 2014
We studied the electron transport properties of micrometre-sized all-Al tunnel junctions (TJs) between 2 and 300 K, in which the AlO x layer grown by O 2 plasma was moderately Ar-ion-milled prior to top electrode deposition. In contrast to the direct tunnelling in the TJs whose barriers are intact (not ion-milled), the zero-bias conductances and the current-voltage characteristics of the TJs as processed are found to be best described by the fluctuation-induced tunnelling conduction mechanism. This observation indicates the formation of nanoscopic incomplete pinholes in the AlO x layer, owing to large junction-barrier interfacial roughness introduced by the ion-milling process. Topographical features revealed by the cross-sectional transmission electron microscopy imaging of the TJ stack conform to this result. This study is of relevance to cases in which ion-milling techniques are applied in tailoring the TJ properties.
Journal of Applied Physics, 2004
Current induced resistance changes were investigated in magnetic tunnel junctions with ultrathin Al-O x barriers. The nonuniformity of the insulator induced a strong coupling between the two magnetic electrodes and no magnetoresistance. However, the current-voltage ͑I-V͒ characteristics at low bias voltages were consistent with a tunnellike behavior. At larger bias voltages, they showed an abrupt change of slope that was reversible for an opposite voltage polarity. The resistance versus current ͑R-I͒ curves exhibited reversible resistance changes that reached over 100%. We interpret this as controlled electromigration in local nanoconstrictions of the barrier.
Aluminum-oxide tunnel barriers with high field endurance
Applied Physics Letters, 2008
We have measured transport properties of all-metallic tunnel junctions, fabricated using rf-plasma-grown aluminum oxide layers and rapid thermal postannealing, in particular, their endurance in electric fields in excess of 10 MV/cm. The results indicate that such junctions may combine high-field endurance ͑corresponding to at least 10 10 write/erase cycles in floating-gate memories͒ and high current density ͑corresponding to 30 ns scale write/erase time͒ at high voltages, with very low conductance ͑corresponding to ϳ0.1 s scale retention time͒ at low voltages. We discuss the improvements necessary for the use of such junctions in advanced floating-gate memories.
Intrinsic Reliability of AlOx-Based Magnetic Tunnel Junctions
IEEE Transactions on Magnetics, 2000
We present a detailed investigation into the intrinsic tunnel barrier reliability in AlOx-based magnetic tunnel junctions (MTJs) as a function of aluminum thickness and oxidation time. The intrinsic reliability is measured as the ramped breakdown voltage ( bd ) at room temperature for both positive and negative polarity. We find that bd generally increases with the resistance-area (RA) product of the MTJ. While this dependence is quite strong at low RA, it gradually weakens for higher RA. At fixed RA, bd also depends on the original Al film thickness with better properties for thicker Al. Finally, we observe a polarity dependence of bd which changes sign as the MTJ goes from thin Al to thick Al. We attribute the polarity dependence to the different quality of the top and bottom interfaces and conclude that the interface emitting the tunneling electrons primarily governs the barrier reliability.