Abstract For chemical vapor deposition (CVD) of HfS2, HfCl4 is commonly used as the Hf precursor, and a sapphire (Al2O3) substrate is preferred to improve film crystallinity. During the HfS2 CVD process using HfCl4 and S precursors on the sapphire substrate, we observed an anomalous morphological evolution due to the chemical interaction between the Al2O3 substrate and HfCl4, particularly when the substrate was exposed to HfCl4 vapor too early, prior to the introduction of S. The excessive HfCl4-induced local chemical etching produced a serrated surface on the substrate, while pyramid-shaped HfO2 crystals (a by-product of chemical etching) and CVD-HfS2 flakes formed on the unetched and etched substrate surface regions, respectively. A mechanism for the observed morphological evolution is proposed based on thermodynamic and kinetic considerations, which emphasizes the importance of precursor supply timing to minimize the potential process-related defects.

中文翻译：

---

在蓝宝石衬底上使用 HfCl4 和 S 化学气相沉积 HfS2 过程中有趣的形态演变

摘要 对于 HfS2 的化学气相沉积 (CVD)，通常使用 HfCl4 作为 Hf 前驱体，并且首选蓝宝石 (Al2O3) 衬底以提高薄膜结晶度。在蓝宝石衬底上使用 HfCl4 和 S 前体的 HfS2 CVD 过程中，我们观察到由于 Al2O3 衬底和 HfCl4 之间的化学相互作用导致的异常形态演变，特别是当衬底在引入 HfCl4 之前过早暴露于 HfCl4 蒸气时S. 过量的 HfCl4 引起的局部化学蚀刻在基板上产生锯齿状表面，而金字塔形 HfO2 晶体（化学蚀刻的副产品）和 CVD-HfS2 薄片分别形成在未蚀刻和蚀刻的基板表面区域。基于热力学和动力学考虑，提出了观察到的形态演化的机制，