Resistive switching mechanism of TiO2 thin films grown by atomic-layer deposition

Abstract

The resistive switching mechanism of 20-to 57-nm-thick TiO 2 thin films grown by atomic-layer deposition was studied by current-voltage measurements and conductive atomic force microscopy. Electric pulse-induced resistance switching was repetitively ͑Ͼ a few hundred times͒ observed with a resistance ratio ӷ10 2 . Both the low-and high-resistance states showed linear log current versus log voltage graphs with a slope of 1 in the low-voltage region where switching did not occur. The thermal stability of both conduction states was also studied. Atomic force microscopy studies under atmosphere and high-vacuum conditions showed that resistance switching is closely related to the formation and elimination of conducting spots. The conducting spots of the low-resistance state have a few tens times higher conductivity than those of the high-resistance state and their density is also a few tens times higher which results in a ϳ10 3 times larger overall conductivity. An interesting finding was that the area where the conducting spots do not exist shows a few times different resistance between the low-and high-resistance state films. It is believed that this resistance change is due to the difference in point defect density that was generated by the applied bias field. The point defects possibly align to form tiny conducting filaments in the high-resistance state and these tiny conducting filaments gather together to form stronger and more conducting filaments during the transition to the low-resistance state.

Investigation of the electroforming process in resistively switching TiO2 nanocrosspoint junctions

“…[3][4][5] However, the early description of the memristor as a discrete device by Chua and the recent transfer of its definition to already known resistively switching materials, especially TiO 2 thin films by Strukov et al draw significant attention to this material system. [6][7][8] The particular physical mechanism is not fully understood yet, but the resistance state depends on the distribution of oxygen and oxygen vacancies, respectively. 9,10 The latter act as n-type dopants that influence the conductivity of the device, in particularly, with regard to an accumulation along the cathode, here Pt.…”

Enhancement of Resistance Switching in Electrodeposited Co-ZnO Films

“…Therefore, the primary requirement for RRAM is to develop a material that possesses resistive switching effect. To date, a number of materials have been found to have resistive switching behavior, for example, ferromagnetic oxide (Pr 1−x Ca x MnO 3 ), doped perovskite oxide (SrZrO 3 ), and binary transition metal oxide (TiO 2 , NiO, ZnO, and Cu 2 O) [1,2,4,6,[8][9][10][11]. Among these materials, only the transition metal oxides are transparent to the visible light due to their large optical band gap.…”

Reversible metal-insulator transition in LaAlO3thin films mediated by intragap defects: An alternative mechanism for resistive switching

“…A number of different mechanisms (17)(18)(19)(20) have been previously demonstrated for resistive switching, such as electric-field-induced oxygen vacancy migration resulting in the formation of conducting filaments (17,18), and reversible metal migration from electrodes (19). Such a variety of field-induced phenomena arise from the complex defects that are present in these oxides.…”