Electrical phenomena in amorphous oxide films

Abstract

In our review we survey the observed properties of metal-insulator-metal devices involving such insulating layers, and discuss the mechanisms which have been proposed for their operation. Further, since the unusual properties may be technologically important, we outline some of the possible uses of these devices and the relevance of the phenomena to the mechanism of corrosion of certain metals.

Resistance switching in transparent magnetic MgO films

“…It is also worth mentioning that visible electroluminescence (photograph in Fig. 1) develops simultaneously with the resistance switching [3,30]. Although not properly understood at this time, the close correlation between this luminescence and the memristor behavior probably indicates that both have the very same origin, i.e., the hole-doping induced by the cation vacancies.…”

“…It is also worth mentioning that these MgO films show a remarkable structural distortion [25], which is taken as an indication of the existence of cation vacancies in our samples [17]. We surmise Mg re-evaporates from the substrate faster than it reacts with O to form MgO on the substrate so that cation vacancies are stabilized, thus resulting in a transparent magnetic film (the transmittance is above 80% in the visible spectrum with saturation magnetization values about 10 emu/cm 3 ) as reported elsewhere [17,18,20]. The sample was then capped with a 100 nm thick transparent conductive indium-tin-oxide (ITO) layer deposited at room temperature through a shadow mask, defining an area of 1 mm in diameter.…”

“…There is another class of devices, usually made in a two terminal metal/insulator/metal structure, which shows voltage-controlled resistance switching [3,4]. Among the various insulators that have been reported thus far, transition metal (sub) oxides such as CuO, NiO, TaO 2 , TiO 2 , NbO 2 and HfO 2 have attracted the most attention.…”

Field-enhanced bulk conductivity and resistive-switching in Ca-doped BiFeO3 ceramics

“…For a typical pellet thickness of ~1.5 mm, these voltages corresponded to a voltage gradient of ~33 to 200 Vcm -1 . The impedance data, 4 presented as both impedance complex plane plots, Figure 3 (a,b) and as log admittance, Y' against log frequency (c,d), were very different without, and with dc bias. With a dc bias, the resistivity of the sample decreased before reaching a steady state, whose total resistivity, in the range ~50-100 cm, was about 3 orders of magnitude less than the initial resistivity ~ 10 5 cm.…”

Experimental study of resistive bistability in metal oxide junctions

“…1a). 11 Experimental observation of such bistability in many materials (including metal oxides and sulphides, amorphous silicon, organic layers with and without embedded metallic grains, and molecular self-assembled monolayers) have been reported in numerous publications starting at least from the 1960s -see an early review 13 and recent reviews. 9,14,15 Moreover, these studies have led to a virtual consensus that the resistive bistability, at least in metal-oxide and amorphous-silicon junctions, 16 is due to the reversible formation and dissolution of one or few highly conducting spots (sometimes called "filaments"), due to field-induced drift of ions (depending on the particular material, either anions or cations) through the amorphous matrix of the layer -see Fig. 1b-d. 9,14,15 Because of this atomic-scale mechanism, the most critical feature of the bistable junctions, especially in the view of their possible applications in VLSI circuits, is the device-to-device reproducibility.…”