Jo Y-R, Kim M-W, Kim B-J
School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Korea.
Nanotechnology. 2016 Oct 28;27(43):435704. doi: 10.1088/0957-4484/27/43/435704. Epub 2016 Sep 23.
Nano-scale VO wires with controlled parameters such as electron-doping have attracted intense interest due to their capability of suppressing the temperature of the metal-insulator transition (MIT). However, because their diameters are smaller than the spatial resolutions of the conventional measuring equipment, the ability to perform a thorough examination of the wires has been hindered. Here, we report the fabrication of a transmission electron microscopy (TEM) grid with an optimum design of SiN windows on which the photolithography for individual electron-doped VO nanowire devices can be safely accomplished, allowing the cross-examination of the structural and electrical properties. TEM dark-field imaging was used to quantitatively investigate the fractions of rutile and M1 phases, and their lattice alignments were observed using high-resolution TEM (HRTEM) with small area diffraction. Moreover, electron energy loss spectroscopy (EELS) revealed that the rutile domain would be created by the strain induced by oxygen vacancies. Importantly, we successfully tuned the transition temperature by changing the rutile fraction while maintaining a high level of resistivity change. The resistivity at room temperature linearly decreased with the rutile fraction, following a simple model. Furthermore, the T dependence of the threshold voltage can be attributed to the Joule heating, exhibiting an identical thermal dependence, irrespective of the rutile fraction.
具有诸如电子掺杂等可控参数的纳米级VO线，因其能够抑制金属-绝缘体转变（MIT）的温度而引起了广泛关注。然而，由于它们的直径小于传统测量设备的空间分辨率，对这些线进行全面检查的能力受到了阻碍。在此，我们报告了一种具有优化设计的氮化硅窗口的透射电子显微镜（TEM）网格的制造方法，在该网格上可以安全地完成对单个电子掺杂VO纳米线器件的光刻，从而能够对其结构和电学性质进行交叉检查。利用TEM暗场成像定量研究了金红石相和M1相的比例，并使用具有小面积衍射的高分辨率TEM（HRTEM）观察了它们的晶格排列。此外，电子能量损失谱（EELS）表明，金红石畴是由氧空位诱导的应变产生的。重要的是，我们在保持高电阻率变化水平的同时，通过改变金红石相比例成功地调节了转变温度。室温下的电阻率随金红石相比例呈线性下降，符合一个简单模型。此外，阈值电压的T依赖性可归因于焦耳热，无论金红石相比例如何，都表现出相同的热依赖性。
