Nandi Sanjoy Kumar, Nath Shimul Kanti, El-Helou Assaad E, Li Shuai, Ratcliff Thomas, Uenuma Mutsunori, Raad Peter E, Elliman Robert G
Department of Electronic Materials Engineering, Research School of Physics , The Australian National University , Canberra , ACT 2601 , Australia.
Department of Mechanical Engineering , Southern Methodist University , Dallas , Texas 75275 , United States.
ACS Appl Mater Interfaces. 2020 Feb 19;12(7):8422-8428. doi: 10.1021/acsami.9b20252. Epub 2020 Feb 7.
Electroforming is used to initiate the memristive response in metal/oxide/metal devices by creating a filamentary conduction path in the oxide film. Here, we use a simple photoresist-based detection technique to map the spatial distribution of conductive filaments formed in Nb/NbO/Pt devices, and correlate these with current-voltage characteristics and in situ thermoreflectance measurements to identify distinct modes of electroforming in low- and high-conductivity NbO films. In low-conductivity films, the filaments are randomly distributed within the oxide film, consistent with a field-induced weakest-link mechanism, while in high-conductivity films they are concentrated in the center of the film. In the latter case, the current-voltage characteristics and in situ thermoreflectance imaging show that electroforming is associated with current bifurcation into regions of low and high current density. This is supported by finite element modeling of the current distribution and shown to be consistent with predictions of a simple core-shell model of the current distribution. These results clearly demonstrate two distinct modes of electroforming in the same material system and show that the dominant mode depends on the conductivity of the film, with field-induced electroforming dominant in low-conductivity films and current bifurcation-induced electroforming dominant in high-conductivity films.
电铸用于通过在氧化膜中创建丝状传导路径来引发金属/氧化物/金属器件中的忆阻响应。在此，我们使用一种基于光刻胶的简单检测技术来绘制在Nb/NbO/Pt器件中形成的导电细丝的空间分布，并将这些与电流-电压特性和原位热反射测量相关联，以识别低电导率和高电导率NbO薄膜中不同的电铸模式。在低电导率薄膜中，细丝随机分布在氧化膜内，这与场诱导的最弱链机制一致，而在高电导率薄膜中，它们集中在薄膜中心。在后一种情况下，电流-电压特性和原位热反射成像表明，电铸与电流分叉到低电流密度和高电流密度区域有关。这得到了电流分布的有限元建模的支持，并表明与电流分布的简单核壳模型的预测一致。这些结果清楚地证明了同一材料系统中两种不同的电铸模式，并表明主导模式取决于薄膜的电导率，场诱导电铸在低电导率薄膜中占主导，电流分叉诱导电铸在高电导率薄膜中占主导。
