An international team of researchers, led by Professor Yu Zou (MSE), is using electrical fields to control the movement of particles. This work has important implications for improving the properties and manufacturing processes of non-destructive and covalent ionic crystals, including semiconductors – crystalline materials that are the main components of electronic chips used for computers and other devices, Scientists use electric fields to control the movement of defects in crystals.
In a new study published in Nature Materials, researchers from U of T Engineering, Dalhousie University, Iowa State University and Peking University show that the optical timing of breaks in monocrystalline zinc sulphide is controlled by use of external electricity.
“This research opens up the possibility of processing materials related to discontinuities, such as mechanical, electrical, thermal and time-varying processes, using electricity, rather than traditional methods,” said MSE PhD student Mingqiang Li, said the first author of the paper.
In materials science, dislocations are linear crystal defects in a crystal structure that have sudden changes in the arrangement of atoms.
It is the most significant defect of crystalline materials, Zou says, because it can affect the strength, ductility, hardness, thermal and electrical conductivities of crystalline materials, such as aircraft steel and silicon used in chips.
In solid crystals, good ductility and formability are often achieved through motion. As such, metals with high mobility can be made into final products through compression, tension, twisting and bending – for example, aluminum cans are hammered into shape.
In contrast, ionic and covalent crystals generally suffer from low reactivity that makes them difficult to repair with functional methods, and are therefore unsuitable for many applications. In the case of semiconductors, they are much less likely to be reproducible and falsified, Zou says.
“The main thing that makes it protest is only in the work pressure, which hinders the design method and the engineering application of many crystalline materials.”
“Our study provides clear evidence for the reversal of uncontrolled impulses, which has been an open question since the 1960s. We also exclude other effects on motion, including Joule heating, electron beam energy, and electrical current.
This study uses transmission electron microscopy to observe changes in zinc sulfide, which is driven by electricity only in the absence of a load. An electric current causes the discharge of negative or positive charges that is caused by an electric current.
The researchers observed a back-and-forth interruption when they changed the direction of the electric current. They also found that the movement of the escapement in the electric field also depends on the nature of their escapement.
Since most semiconductors are copper because of their low dislocation movement, the electric field-controlled dislocation movement in this new study can be used to improve their mechanical reliability and formability, Li says.
“In addition, our work provides an alternative method for reducing defect density in aging semiconductors, insulators, and devices that do not require a wear-and-tear process, which uses heat over time to reduce defects of things,” he adds.
Although the initial study focused on zinc sulfide, the team plans to investigate many different materials, from covalent crystals to ionic crystals.
“As we work to implement this technology, our goal is to work with manufacturers and the manufacturing industry, especially the semiconductor industry, to develop new production methods to reduce the density of defects and improve the properties and performance of semiconductors,” said Zou.
Source: University of Toronto.
