Zafar Amina, Younas Muhammad, Fatima Syeda Arooj, Qian Lizhi, Liu Yanguo, Sun Hongyu, Shaheen Rubina, Nisar Amjad, Karim Shafqat, Nadeem Muhammad, Ahmad Mashkoor
Nanomaterials Research Group, Physics Division, PINSTECH, Islamabad 44000, Pakistan.
Central Analytical Facility Division, PINSTECH, Islamabad 44000, Pakistan.
Nanoscale. 2021 Oct 1;13(37):15711-15720. doi: 10.1039/d1nr03136h.
The synthesis of one-dimensional heterostructures having high dielectric constant and low dielectric loss has remained a great challenge. Until now, the dielectric performance of ZnO-ZnS heterostructures was scarcely investigated. In this work, large-scale ZnO-ZnS heterostructures were synthesized by employing the chemical vapor deposition method. High resolution transmission electron microscopy (HRTEM) confirms the formation of heterostructures. X-ray photoelectron spectroscopy (XPS) shows that S atoms fill up the oxygen vacancy (V) in ZnO, leading to the suppression of charge carrier's movement from ZnO to ZnS; instead there is charge transfer from ZnS to ZnO. Conductivity mismatch between adjacent ZnO and ZnS materials leads to the accumulation of free charges at the interface of the heterostructure and can be considered as a capacitor-like structure. The electrical behaviors of the potential phases of ZnO, ZnS and the ZnO-ZnS heterostructure are well interpreted by a best fitted equivalent circuit model. Each heterostructure acts as a polarization node with a specific flip-flop frequency and all such nodes form continuous transmission of polarization, which jointly increase the dielectric energy-storage performance. The orientational polarization of the polarons and Zn-V dipoles present at the heterostructure interface contributes to the frequency stable dielectric constant at ≥10 Hz. Our findings provide a systematic approach to tailor the electronic transport and dielectric properties at the interface of the heterostructure. We suggest that this approach can be extended for improving the energy harvesting, transformation and storage capabilities of the nanostructures for the development of high-performance energy-storage devices.
合成具有高介电常数和低介电损耗的一维异质结构仍然是一个巨大的挑战。到目前为止，ZnO-ZnS异质结构的介电性能几乎没有得到研究。在这项工作中，采用化学气相沉积法合成了大规模的ZnO-ZnS异质结构。高分辨率透射电子显微镜（HRTEM）证实了异质结构的形成。X射线光电子能谱（XPS）表明，S原子填充了ZnO中的氧空位（V），导致电荷载流子从ZnO向ZnS移动受到抑制；相反，存在从ZnS到ZnO的电荷转移。相邻的ZnO和ZnS材料之间的电导率失配导致异质结构界面处自由电荷的积累，并且可以被视为类似电容器的结构。通过最佳拟合等效电路模型很好地解释了ZnO、ZnS和ZnO-ZnS异质结构的潜在相的电学行为。每个异质结构都作为一个具有特定触发器频率的极化节点，所有这些节点形成连续的极化传输，共同提高介电储能性能。在异质结构界面处存在的极化子和Zn-V偶极子的取向极化有助于在≥10 Hz时实现频率稳定的介电常数。我们的发现提供了一种系统的方法来调整异质结构界面处的电子传输和介电性能。我们建议这种方法可以扩展用于提高纳米结构的能量收集、转换和存储能力，以开发高性能储能器件。
