Advanced Materials
Advanced Materials
4 years ago

Nanometer-Scale Phase Transformation Determines Threshold and Memory Switching Mechanism

Nanometer-Scale Phase Transformation Determines Threshold and Memory Switching Mechanism
Kyungjoon Baek, Jae-Bok Seol, Hyunsang Hwang, Byeong-Gyu Chae, Chan-Gyung Park, Jeong-Hwan Song, Sang-Ho Oh
Creation of nanometer-scale conductive filaments in resistive switching devices makes them appealing for advanced electrical applications. While in situ electrical probing transmission electron microscopy promotes fundamental investigations of how the conductive filament comes into existence, it does not provide proof-of-principle observations for the filament growth. Here, using advanced microscopy techniques, electrical, 3D compositional, and structural information of the switching-induced conductive filament are described. It is found that during in situ probing microscopy of a Ag/TiO2/Pt device showing both memory- and threshold-switching characteristics, a crystalline Ag-doped TiO2 forms at vacant sites on the device surface and acts as the conductive filament. More importantly, change in filament morphology varying with applied compliance currents determines the underlying switching mechanisms that govern either memory or threshold response. When focusing more on threshold switching features, it is demonstrated that the structural disappearance of the filament arises at the end of the constricted region and leads to the spontaneous phase transformation from crystalline conductive state into an initial amorphous insulator. Use of the proposed method enables a new pathway for observing nanosized features in a variety of devices at the atomic scale in three dimensions. Phase transformation on the nanometer scale determines the electrical, compositional, and structural features of conductive filaments in a Ag/TiO2/Pt device. During in situ probing, a nanometer-sized crystalline Ag-doped TiO2 acts as a conductive filament. Focusing more on threshold switching feature, the structural disappearance of the filament resembles phase transformation from crystalline conductive state into an initial amorphous insulator.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/adma.201701752

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