中文摘要：

在以前工作的基础上，进一步研究了SrTiO3（001）（STO）衬底上单层FeSe超导薄膜的分子束外延生长。首先，通过去离子水刻蚀、盐酸溶液腐蚀和纯氧气氛中退火等步骤，获得台阶有序、具有单一TiO2终止的原子级平整表面的STO衬底，这是前提条件。这个过程中酸的选择和退火过程中氧的流量是最为关键的因素。其次，在FeSe薄膜的分子束外延生长中，选择适当的Fe源和Se源束流以及衬底温度是关键因素。如选择适当，生长模式为step-flow生长，这时得到的FeSe薄膜将是原子级平整的。最后一步为退火，这个过程会增强FeSe薄膜结晶性以及它与SrTiO3衬底间的结合强度。

英文摘要：

Based on our previous work, we have systematically investigated the molecular beam epitaxy growth of single unit-cell FeSe films on SrTiO3（001） substrates and studied the surface morphology by scanning tunneling microscopy. We found that there are three key steps to obtain large-scale uniform one unit-cell superconducting FeSe films. First, the STO（001） substrates should be treated by HCl etching and thermal annealing under oxygen flux so that a specific TiO2-terminated STO（001） surface with well-defined step-terrace structure could be obtained. Second, the Fe and Se fluxes and substrate temperature have to be controlled delicately. At last, post-growth annealing is also critical, which can remove extra Se adatoms, and more importantly facilitate the necessary electron transfer for superconductivity transition.