Defect-induced photoluminescence of strontium titanate and its modulation by electrostatic gating

TL;DR

This study investigates how defect-induced photoluminescence in strontium titanate can be modulated by electrostatic gating, revealing temperature-dependent PL peaks and a 20% intensity increase at low temperature.

Contribution

It demonstrates the activation of multicolored PL peaks in irradiated SrTiO3 and their modulation via electrostatic gating, linking PL changes to structural phase transitions.

Findings

Irradiation activates blue, green, and infrared PL peaks.

PL properties change abruptly below ~100 K due to structural transition.

Electrostatic gating enhances PL intensity by ~20% at 20 K.

Abstract

The photoluminescence (PL) spectra of Ar-ion irradiated single crystals of SrTiO3 (STO) excited by the 325 nm line of a He-Cd laser are compared with those of pristine crystals, epitaxial films, and amorphous layers of STO at several temperatures down to 20 K. The 550 eV Ar-beam irradiation activates three distinctly visible PL peaks: blue (~430 nm), green (~550 nm), and infrared (~820 nm) at room temperature, making the photoluminescence multicolored. The abrupt changes in PL properties below ~100 K are discussed in relation with the antiferrodistortive structural phase transition in SrTiO3 from cubic to tetragonal symmetry, which makes it a direct bandgap semiconductor. The photoluminescence spectra are also tuned by an electrostatic gate field in a field-effect transistor geometry. At 20 K, we observed a maximum increase of ~20% in PL intensity under back gating of SrTiO3.