TeYu Chien, a UW assistant professor in the Department of Physics and Astronomy, uses a low-temperature scanning tunneling microscope in his lab to observe the effect of spontaneously-forming electric fields on nanomaterials. Image: University of Wyoming.Spontaneously-forming electric fields can alter the mechanical properties of nanomaterials, say University of Wyoming (UW) researchers.
Led by TeYu Chien, a UW assistant professor in the Department of Physics and Astronomy, the researchers determined that electric fields can alter the fracture toughness of the kind of nanomaterials used in state-of-the-art electronic devices. This represents the first evidence of electric fields changing fracture toughness at a nanometer scale.
Chien is the lead author of a paper reporting this work in Scientific Reports. Other researchers who contributed to the paper are from the University of Arkansas, the University of Tennessee and the Argonne National Laboratory.
Chien and his research team studied the interface between two ceramic materials: lanthanum nickelate and strontium titanate with a small amount of niobium. These two ceramic materials were chosen because one is a metallic oxide while the other is a semiconductor. When these two materials come into contact with each other, an intrinsic electric field spontaneously forms in a region known as the Schottky barrier near the interface between them, Chien explains.
This intrinsic electric field is an inevitable phenomenon that occurs at metal/semiconductor interfaces. However, the effects of this electric field on the mechanical properties of materials have rarely been studied, especially for nanomaterials, but this is what Chien and his team have now done by studying the two ceramics with scanning tunneling microscopy and spectroscopy.
"The electric field changes the inter-atomic bond length in the crystal by pushing positively and negatively charged ions in opposite directions," explains Chien. "Altering bond length changes bond strength. Hence, the mechanical properties, such as fracture toughness.
"The whole picture is this: the intrinsic electric field in the Schottky barrier was created at the interfaces. This then polarized the materials near the interfaces by changing the atomic positions in the crystal. The changed atomic positions altered the inter-atomic bond length inside the materials to change the mechanical properties near the interfaces."
These observations pave the way for a better understanding of the effect of electric fields at metal/semiconductor interfaces. Such an understanding is extremely important for optimizing the performance of nanoelectromechanical systems (NEMS), which are devices such as actuators that integrate electrical and mechanical functionalities at the nanoscale.
This story is adapted from material from the University of Wyoming, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.