Prospect of rich correlated phases in two-dimensional oxide perovskites“Given the outstanding physical and chemical properties of oxide perovskites and novel phenomena emergent at the monolayer limit, this work opens new possibilities in the exploration of quantum behaviors in strongly correlated two-dimensional materials”Xiaoqing Pan
Researchers have developed oxide perovskite crystals in flexible, free-standing layers. Conventional 2D materials possess useful electronic properties, such as high-temperature superconductivity when at reduced dimensionality, and here scientists from the University of California, Irvine, with collaborators from China's Nanjing University and the University of Nebraska, reported a new process for fabricating freestanding ultrathin crystalline oxide perovskite films with high crystalline quality down to the monolayer limit. Such 2D materials are promising building blocks in multifunctional high-tech devices for energy and quantum computing.
While they have a range of interesting physical and chemical properties, it is not easy to produce oxide perovskites in flat layers because of the strongly bonded structure of their crystals. However, as reported in Nature [Ji et al. Nature (2019) DOI: 10.1038/s41586-019-1255-7], the technique of molecular beam epitaxy was used to develop the thin oxide films on a layer-by-layer basis, without any thickness limitation, on a template with a water-dissolvable buffer, before they were etched and transferred onto any desired substrate.
The ability to successfully synthesize high-quality 2D oxide perovskite films could open up new opportunities for emergent 2D correlated quantum phases, as well as new possibilities for correlated 2D phases and interfacial phenomena, and as the crystals have strongly correlated effects it is hoped they will exhibit similar qualities to graphene. The team also reviewed the work at atomic resolution using aberration-corrected transmission electron microscopy to provide feedback on the optimization of film growth conditions.
As co-author Xiaoqing Pan said, “Given the outstanding physical and chemical properties of oxide perovskites and novel phenomena emergent at the monolayer limit, this work opens new possibilities in the exploration of quantum behaviors in strongly correlated two-dimensional materials”. The freestanding 2D oxide perovskites can be directly transferred onto a silicon wafer, which could allow multifunctional electronic devices by combining the properties of both oxides and conventional semiconductors.
There are a range of oxide perovskites with very different properties, so the researchers could look to synthesize 2D sheets of various oxide perovskites and explore their exotic 2D electronic properties. For instance, stacking various oxide perovskite films together could lead to new findings of novel quantum phases, and flexo-related phenomena under external stimuli field is also an area worth investigating.