In recent years, the two-dimensional electron gas (2DEG) in translated metal oxide heterostructures has attracted extensive attention due to their relative higher mobility, superconductivity and other fascinating physical phenomena.At present, oxide heterostructures are generally synthesized through epitaxial growth on lattice-matched single-crystal substrates. However, their integration with semiconductor substrates for electronic applications is challenging due to the large lattice mismatch and the incompatible growth conditions, hindering their electronic applications.
In this work, we fabricated freestanding films with an atomically precise control of the thickness and surface, and the integration of 2DEG with silicon substrate by a combination of reactive molecular beam epitaxy (OMBE) and wet etching transfer technique. In the experiments, we first transferred TiO2-teminated SrTiO3 (STO) film onto Si by using Sr3Al2O6 (SAO) as a sacrificial buffer layer. Subsequently, amorphous-Al2O3 (aAO) film was deposited on STO/Si, which results in 2DEG with a high mobility (as shown in Figure a). Both the interfacial Ti valance state evolution and the transport results verify that the high mobility 2DEG locates at the interface of amorphous Al2O3/SrTiO3 (as shown in Figure b).
In contrast, directly growing and transferring freestanding aAO/STO heterostructures onto Si only yields insulating interface, which is most likely due to the oxygen backfilling through the thin STO layer during the transferring process.
In short, high mobility 2DEG at oxide interface is successfully integrated on silicon wafer by a growth and transfer method, providing a new to integrate high mobility oxide 2DEG on Si for novel electronic applications.
The work was recently published in ACS Applied Materials & Interfaces:https://doi.org/10.1021/acsami.2c18934.
Leyan Nian (PhD student) is the first author of the paper, and Prof. Yuefeng Nie, Prof. Yufeng Hao and Prof. Deng Yu are the corresponding authors of the paper. Tingting Zhang, Haoying Sun, Tianyi Gao and Yueying Li provided important support for film preparation, transport characterization and mechanism interpretation. Deng Yu, Jiyi Li and Zhichao Wang provided the electron microscopy characterization support for this work.
Figure (a) Schematic diagrams of fabricating freestanding aAO/STO heterostructures on Si. (b) microscopic characterizations and transport measurements of aAO/STOheterostructure on Si.
