Could electric fields help develop efficient semiconductors?

A team of researchers from POSTECH, Seoul National University, and Soongsil University has induced polarisation and polarity in metallic substances. In the field of material science, the phenomena of polarisation and polarity have conventionally been associated with insulators. Polarisation is a redistribution of the centres of positive and negative charges within an object or material, while polarity is the particular state of an object or material — either positive or negative, with reference to the two poles.

Researchers have now discovered a method to induce and control polarisation and polarity states within metals. These research findings could help mitigate power losses attributed to semiconductors and extend the lifespan of batteries integrated into electronic devices. Existing technologies have posed limitations to date despite the extensive research to achieve polarisation and polarity in metals.

Free electrons within metals, given their name, exhibit unrestricted movement, making it difficult to align them in specific directions to induce polarisation or polarity states. The symmetric structure of metal crystals at both ends also poses challenges in inducing these electrical effects. However, the researchers used flexoelectric fields to implement polarisation and polarity states within metals. This type of field arises when the surface of an object undergoes non-uniform deformation, allowing for the manipulation of charge movement and electrical characteristics by altering the lattice structure of metals.

The researchers applied external pressure to strontium ruthenate (SrRuO₃) in the field of electronic components and semiconductors, generating a flexoelectric field. This metal oxide — characterised by heteroepitaxy, where crystals of strontium and ruthenium oxide with different shapes grow in the same direction — possesses a centrosymmetric structure.

The flexoelectric field altered the electronic interactions and lattice structure within strontium ruthenate, leading to the induction of polarisation within the metal, causing a transformation in its electrical and mechanical properties and breaking the previously central symmetric structure. The researchers believe that their findings will help craft highly efficient devices within the semiconductor and electrical fields.

The research findings were published in the international physics journal Nature Physics.

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