Sinha Abhinav, Verma Manvi, K M Nandeesh Kumar, Kumar Keerthana S, Govind Rajan Ananth, Singh Akshay
Department of Physics, Indian Institute of Science Bengaluru Karnataka 560012 India
Department of Chemical Engineering, Indian Institute of Science Bengaluru Karnataka 560012 India
Nanoscale Adv. 2025 Apr 23. doi: 10.1039/d5na00202h.
Chemical vapor deposition (CVD) is the most widespread approach for two-dimensional (2D) material synthesis, yet control of nucleation density remains a major hurdle towards large-area growth. We find that precursor flux, a function of gas velocity and precursor concentration, is the critical parameter controlling nucleation. We observe that for a vertically aligned substrate, the presence of a cavity/slot in the substrate-supporting plate creates an enhanced growth zone for 2D-MoS. The effect of this confined space on nucleation density is experimentally verified by electron microscopy. To understand this intriguing observation, we developed a hyper-realistic multiphysics computational fluid dynamics model, , a digital twin of our CVD reactor, which reveals that space confinement achieves nearly-zero gas velocities. Digital twin-informed calculations indicate a significantly lower metal precursor flux at the confined space during the initial stages of growth, while precursor concentration is uniform across the substrate. The digital twin also makes an important prediction regarding a large time-lag between the set temperature, reactor environmental temperature, and substrate temperature, with implications for nucleation and growth. We offer a framework for designing confined spaces to control nucleation regulating precursor flux, and for simulating reactor parameters for rapid optimization the digital-twin model.
化学气相沉积（CVD）是二维（2D）材料合成中应用最广泛的方法，但成核密度的控制仍然是大面积生长面临的主要障碍。我们发现前驱体通量（气体速度和前驱体浓度的函数）是控制成核的关键参数。我们观察到，对于垂直排列的衬底，衬底支撑板中的腔/槽的存在为二维MoS创造了一个增强的生长区域。通过电子显微镜实验验证了这种受限空间对成核密度的影响。为了理解这一有趣的观察结果，我们开发了一个超真实的多物理场计算流体动力学模型，即我们CVD反应器的数字孪生模型，该模型揭示了空间限制实现了几乎为零的气体速度。基于数字孪生模型的计算表明，在生长初期，受限空间处的金属前驱体通量显著降低，而前驱体浓度在整个衬底上是均匀的。数字孪生模型还对设定温度、反应器环境温度和衬底温度之间的较大时间滞后做出了重要预测，这对成核和生长有影响。我们提供了一个框架，用于设计受限空间以控制成核、调节前驱体通量，并通过数字孪生模型模拟反应器参数以实现快速优化。
