Quality enhancement of low temperature metal organic chemical vapor deposited MoS2: an experimental and computational investigation
Quality enhancement of low temperature metal organic chemical vapor deposited MoS2: an experimental and computational investigation
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DOI：
10.1088/1361-6528/ab2c3a
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发表时间：
2019-09-27
期刊：
影响因子：
3.5
通讯作者：
Haque, Aman
中科院分区：
文献类型：
--
作者：
Islam, Zahabul;Zhang, Kehao;Haque, Aman
化学气相沉积二硫化钼的电子质量是结晶度的函数，结晶度随沉积温度的降低而下降。传统的热退火可以提高质量，但需要很高的温度。在这项研究中，我们研究了一种新的低温（室温至400℃）退火工艺，该工艺利用了电流通过时的电子风力。在这里，当电子在晶格或晶界（GBs）中遇到缺陷时，中等电流密度会产生原子尺度的机械力。假设这种力可以在没有温度场的情况下显著提高缺陷迁移率，我们使用原位透射电子显微镜和分子动力学模拟演示了这一过程。在400℃沉积的单层金属有机化学气相沉积MoS2，在低至20℃的温度下进行后处理。实验结果表明，电导率提高了5倍，电子衍射图表明晶粒生长明显。衍射上的离散点表明即使在室温下也有高结晶度的演变。我们的计算模型显示了修复晶格缺陷以及重定向GBs背后的机制。退火前后试样的力学性能模拟也反映了试样微观结构的增强。
Electronic quality of chemical vapor deposited MoS2 is a function of crystallinity, which tends to decline with decrease in deposition temperature. Conventional thermal annealing can improve the quality but requires very high temperatures. In this study, we investigate a novel low temperature (room temperature to 400 degrees C) annealing process that exploits the electron wind force during passage of current. Here, moderate current density gives rise to atomic scale mechanical force whenever the electrons encounter defects in the lattice or grain boundaries (GBs). After hypothesizing that this force can significantly enhance defect mobility without any temperature field, we demonstrate the process using in situ transmission electron microscope and molecular dynamics simulation. Monolayer metal organic chemical vapor deposited MoS2 deposited at 400 degrees C was post processed at temperature as low as 20 degrees C. Experimental results show five times enhancement in electrical conductivity, which is supported by electron diffraction patterns indicating significant grain growth. Discrete spots in diffraction indicate evolution of high crystallinity even at room temperature. Our computational model shows the mechanisms behind healing lattice defects as well as reorienting the GBs. The enhancement in microstructure of the specimen is also reflected in mechanical properties simulations on pre- and post-annealed specimens.