Consiglio Nazionale delle Ricerche-Istituto per lo studio dei Materiali Nanostrutturati (CNR- ISMN), via P. Gobetti 101, 40129 Bologna, Italy.
University of California, Santa Barbara Electrical & Computer Engineering Harold Frank Hall.
Sci Rep. 2014 Feb 26;4:4196. doi: 10.1038/srep04196.
Nanoparticles (NPs) embedded in a conductive or insulating matrix play a key role in memristors and in flash memory devices. However, the role of proximity to the interface of isolated NPs has never been directly observed nor fully understood. Here we show that a reversible local switching in tunnel conductivity can be achieved by applying an appropriate voltage pulse using the tip of a scanning tunnelling microscope on NPs embedded in a TiO2 matrix. The resistive switching occurs in the TiO2 matrix in correlation to the NPs that are in proximity of the surface and it is spatially confined to the single NP size. The tunnel conductivity is increased by more than one order of magnitude. The results are rationalized by a model that include the charge of NPs that work as a nano floating gate inducing local band bending that facilitates charge tunnelling and by the formation and redistribution of oxygen vacancies that concentrate in proximity of the charged NPs. Our study demonstrates the switching in tunnel conductivity in single NP and provides useful information for the understanding mechanism or resistive switching.
纳米粒子（NPs）嵌入在导电或绝缘基质中，在忆阻器和闪存器件中起着关键作用。然而，孤立纳米粒子接近界面的作用从未被直接观察到，也没有被完全理解。在这里，我们展示了通过使用扫描隧道显微镜的尖端施加适当的电压脉冲，可以在 TiO2 基质中嵌入的 NPs 上实现隧道电导率的可逆局部开关。电阻开关发生在与表面附近的 NPs 相关的 TiO2 基质中，并且空间局限于单个 NP 的尺寸。隧道电导率增加了一个数量级以上。结果通过一个模型得到了合理化，该模型包括作为纳米浮栅的 NPs 的电荷，这诱导了局部能带弯曲，从而促进了电荷隧穿，以及氧空位的形成和再分布，这些氧空位集中在带电 NPs 的附近。我们的研究证明了单个 NP 中的隧道电导率开关，并为理解电阻开关机制提供了有用的信息。
