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Perovskite Crystals Defect Might Lead To Transparent Conductor

A defect found in barium stannate (BaSnO3) perovskite crystals could one day lead to a new type of transparent conductive film, according to scientists at the University of Minnesota.

The defect is a one-dimensional (line) defect that runs through single crystals of the material aligned with one of the crystal axis.

“The conductive nature and preferential direction of these metallic line defects mean we can make a material that is transparent like glass and at the same time very nicely directionally conductive like a metal,” said chemical engineer Professor Andre Mkhoyan. “This gives us the best of two worlds. We can make windows or new types of touch screens transparent and at the same time conductive. This is very exciting.”

The discovery was made in lanthanum-doped BaSnO3 using transmission electron microscopy on films grown by molecular beam epitaxy on a LaAlO3 substrate.

Lanthanum (yellow in the diagram) replaces some barium atoms which locally distorts the crystal lattice.

When two lanthanum atoms do this close together, they can push tin atoms (purple) between them together. This can happen in layer after layer of crystal, with the defects aligned, resulting in columns of paired tin atoms – viewed from the top in the diagram.

“We easily spotted these line defects in the high-resolution scanning transmission electron microscopy images of these BaSnO3 thin films because of their unique atomic configuration and we only saw them in the plan view,” said fellow researcher Hwanhui Yun.

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Conductivity is therefore up though the thickness of the film, while for touch screens it needs to be across the film.

As the metallic line defects propagate in a known direction, researchers can potentially control how or where line defects appear, and potentially engineer them into useful transparent conductive materials, according to the university.

Source: electronicsweekly

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