Wang Shujuan, Zhao Jie, Tong Tao, Cheng Baochang, Xiao Yanhe, Lei Shuijin
ACS Appl Mater Interfaces. 2019 Apr 24;11(16):14932-14943. doi: 10.1021/acsami.9b00267. Epub 2019 Apr 9.
ZnO nanostructures are exceedingly important building blocks for nanodevices due to their wide band gap and large exciton binding energy. However, their electronic transport characteristics are unstable and unrepeatable with external environment variation. Here, we demonstrate that electron transport of an individual ZnO nanowire-based device with the two same electrodes can be controllably modulated by applying a relatively large uni-/bidirectional bias. After being modulated, moreover, their electrical properties can well be maintained at relatively low operation bias and room temperature, demonstrating a memory behavior. The presence of surface states related to lattice periodicity breaking and traps associated with oxygen vacancy (V) and zinc interstitial (Zn) deep-level defects plays a crucial role in tunable electron transport with a memory feature. For the single nanowire-based two-terminal device, two back-to-back connected surface barrier diodes with series resistance are formed. The filling and emptying of traps near two end electrodes can remarkably adjust the width and height of the surface barrier. At a relatively low bias, the unmodulated conductance is governed by the electron hopping of bulk traps since the height of emptied traps is higher than that of the surface barrier, whereas at a relatively large bias, it is dominated by thermion emission due to a dramatic decrease of the surface barrier width resulting from the electron injection into traps from a negative electrode. Moreover, it will be beneficial for a thin surface barrier to penetrate UV light and separate photoexcited electron-hole pairs. After being asymmetrically modulated by a unidirectional injection, it can be successfully applied to realize a self-driven UV photodetector based on a photovoltaic effect in the symmetrical two-electrode structure. Our work provides a new route to tune electrical properties of nanostructures, which may inspire the development of novel electronic and optoelectronic devices.
由于具有宽带隙和大激子结合能，氧化锌纳米结构是纳米器件极其重要的构建块。然而，其电子输运特性会随着外部环境变化而不稳定且不可重复。在此，我们证明，通过施加相对较大的单向/双向偏压，可以可控地调制具有两个相同电极的单个氧化锌纳米线基器件的电子输运。此外，经过调制后，其电学性质在相对较低的工作偏压和室温下能够很好地保持，呈现出记忆行为。与晶格周期性破坏相关的表面态以及与氧空位（V）和锌间隙（Zn）深能级缺陷相关的陷阱的存在，在具有记忆特性的可调电子输运中起着关键作用。对于基于单纳米线的两端器件，形成了两个背靠背连接且带有串联电阻的表面势垒二极管。两个端部电极附近陷阱的填充和清空可以显著调节表面势垒的宽度和高度。在相对较低的偏压下，未调制的电导由体陷阱中的电子跳跃控制，因为清空陷阱的高度高于表面势垒，而在相对较大的偏压下，由于电子从负极注入陷阱导致表面势垒宽度急剧减小，电导由热电子发射主导。此外，薄表面势垒有利于穿透紫外光并分离光激发的电子 - 空穴对。经过单向注入不对称调制后，它可以成功应用于在对称两电极结构中基于光伏效应实现自驱动紫外光电探测器。我们的工作为调节纳米结构的电学性质提供了一条新途径，这可能会激发新型电子和光电器件的发展。
