A team of scientists and engineers at the University of Minnesota Twin Cities has developed a new method (A new technique to create self-supporting membranes of “smart” materials) to create thin films of perovskite oxide semiconductors, a class of “intelligent” materials with unique switchable properties in response to stimuli such as light, magnetic fields or electric fields.
This research will allow researchers to use these materials and even combine them with other emerging nanoscale materials to make smart devices such as sensors, smart textiles and flexible electrical appliances.
This article is published in Science Advances, a peer-reviewed scientific journal published by the American Association for the Advancement of Science (AAAS).
The production of materials in the form of soft materials enables their inclusion in small materials for electronic devices. Many thin films are made using a technique called epitaxy, which involves depositing atoms of material into a substrate, or template, to create a thin, atomic layer at a time. However, many thin films produced by epitaxy are “stuck” to their host substrate, which limits their use. If the thin film is removed from the seed to form a self-supporting skin, it works better.
A team led by the University of Minnesota has discovered a new way (A new technique to create self-supporting membranes of “smart” materials) to create a membrane of a metal oxide – strontium titanate – and their process overcomes many of the problems that have hindered the synthesis of self-supporting metal oxide films in the past.
“We have created a process where we can make a self-supporting membrane of almost any oxide, remove it, and then transfer it to any subject of interest that we want,” Bharat Jalan, director said. The essay of the article and the professor and Shell Chair in the Department of Chemical Engineering and Materials Science at the University of Minnesota said. “Now, we can benefit from the functionality of these materials by combining them with other nanoscale materials, which will make many devices work more efficiently.”
Making a self-supporting membrane of “smart” oxide materials is a challenge because the atoms are connected in three dimensions, unlike in two-dimensional materials, such as graphene. One way to create membranes from oxide materials is using a technique called optical epitaxy, which uses a layer of graphene as an interface between the substrate and the thin film.
This method makes the thin oxide film to form a thin film and remove it, like a sheet, from the fruit, creating a self-supporting membrane. However, the biggest obstacle to using this method with metal oxides is that the oxygen in the material causes the graphene to come into contact, destroying the sample.
Using hybrid molecular beam epitaxy, a technique developed by Jalan’s lab at the University of Minnesota, the researchers were able to overcome this problem by using oxygen-treated titanium. In addition, their system allows automatic stoichiometric control, which means that they can control the composition automatically.
“We have shown for the first time, and finally by doing a lot of research, that we have a new method that allows us to create complex oxide and ensure that graphene is not oxidized. This is a big step in the science of synthesis, Jalan said. “But we now have a way to make these complex oxide membranes with stoichiometric control automatically. No one else can do that.”
Materials scientists and Jalan’s team are working closely with engineering researchers from Professor Steven Koester’s laboratory in the Department of Electrical and Computer Engineering at the University of Minnesota, which focuses on 2D material design.
“These complex oxides are a broad class of materials that have many really important purposes for them,” said Koester, who also conducted the study and director of the Minnesota Nano Center at the University of Minnesota Twin Cities. “Now we can imagine using them to make small transistors for electronic devices, and in many other applications, including flexible sensors, smart textiles and non-volatile memories.”
