Chen Zheng, Zhang Meng, Ren Tianshuang, Xie Yanwu
Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China.
J Phys Condens Matter. 2019 Dec 18;31(50):505002. doi: 10.1088/1361-648X/ab42af.
Numerous studies have shown that oxygen vacancies play an important role on the formation of two-dimensional electron gas (2DEG) at SrTiO-based heterointerfaces. Previously, it is widely believed that the main mechanism is that the oxygen vacancies in SrTiO directly contribute electrons to the 2DEG. Here, we performed transport measurements during the creation of 2DEG for depositing amorphous LaAlO on SrTiO substrates and related heterostructures. Our result suggests that, unlike the previous viewpoint, in this kind of 2DEG the determinant mechanism is the electron transfer from the oxygen vacancies in the film grown on SrTiO, rather than the oxygen vacancies in SrTiO themselves. This effect is so striking that an amorphous film of less than 10% monolayer coverage on SrTiO, or equivalently 0.04 nm, can already generate a highly conducting 2DEG. The present result may have a general implication and provide a possible way to understand the long-standing debate on the origin of 2DEG at SrTiO-based heterointerfaces.
大量研究表明，氧空位在基于SrTiO的异质界面二维电子气（2DEG）的形成过程中起着重要作用。此前，人们普遍认为主要机制是SrTiO中的氧空位直接为2DEG贡献电子。在此，我们在将非晶LaAlO沉积在SrTiO衬底及相关异质结构上以形成2DEG的过程中进行了输运测量。我们的结果表明，与之前的观点不同，在这种2DEG中，决定性机制是来自生长在SrTiO上的薄膜中的氧空位的电子转移，而非SrTiO本身的氧空位。这种效应非常显著，以至于在SrTiO上覆盖度小于10%单层、即等效于0.04nm的非晶薄膜，就能产生高导电性的2DEG。目前的结果可能具有普遍意义，并为理解关于基于SrTiO的异质界面处2DEG起源的长期争论提供了一种可能的途径。
