Enhanced Photoconductivity at Dislocations in SrTiO₃

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Physics

Background:

• Crystallographic line defects, known as dislocations, are typically detrimental to semiconductor properties.
• However, their role in oxide semiconductors remains less understood, particularly concerning electronic and photoelectric functionalities.

Purpose of the Study:

• To investigate the impact of controlled dislocations on the photoconductivity of strontium titanate single crystals.
• To explore the potential of dislocations in tailoring photoelectric properties of oxide semiconductors.

Main Methods:

• Controlled plastic deformation of strontium titanate single crystals to introduce ordered dislocations.
• Nanoscale conductive atomic force microscopy to probe local photoconductivity around dislocation cores.
• Macroscopic in-plane measurements to assess global photoresponse.

Main Results:

• Dislocations were controllably introduced in strontium titanate via two slip systems with distinct mesoscopic arrangements.
• Significant enhancement of photoconductivity was observed around dislocation cores at the nanoscale.
• Different mesoscopic arrangements of dislocations led to orders of magnitude variation in global photoconductivity.
• Evidence for a bulk photovoltaic effect associated with dislocation strain fields was observed.

Conclusions:

• Dislocations in oxide semiconductors, specifically strontium titanate, can enhance photoconductivity, contrary to their effect in traditional semiconductors.
• The arrangement of dislocations critically influences the macroscopic photoresponse, offering a method for tuning photoelectric properties.
• Dislocations represent a promising research direction for developing novel photoelectric functionalities in oxide materials.